Ventilation – Electronic cabinet
Reexamination Certificate
1998-10-29
2001-04-17
Joyce, Harold (Department: 3749)
Ventilation
Electronic cabinet
C361S695000
Reexamination Certificate
active
06217440
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an improved air mover system and, more particularly, to an air mover system adapted to reduce reverse air flow.
BACKGROUND OF THE INVENTION
There is an ever-increasing need for electronic devices and systems having improved reliability. One potential source of failure for an electronic system is its cooling system. The electronic components of such systems typically generate a considerable amount of heat in an enclosed or semi-enclosed space. It is often necessary to provide a cooling system in order to prevent temperature gradients that could compromise the function of such electronic components.
One method of cooling is the use of an air mover such as a fan or impeller in order to establish air flow across the electronic components. Such air flow facilitates the dissipation of generated heat by convection heat transfer. In some cooling systems, multiple air movers are mounted in a bank arrangement wherein each of the air movers moves a portion of the air that is being used to cool the electronic system, and the air movers in combination provide the cooling capacity necessary to cool the electronic system.
Multiple air movers are sometimes mounted to move air along air flow paths that are arranged in a parallel orientation. This is not to say that the air flow paths are arranged parallel with respect to one another in the geometric sense; instead, such parallel orientation refers to the movement by each of the air movers of a separable portion of the air flow so that the combined effort of the air movers is sufficient to generate a total air flow requirement for suitable heat transfer.
It has been discovered, however, that the failure of one or more air movers in a system having multiple air movers can change the air-flow pattern in a manner that compromises the dissipation of heat generated by the electronic system. For purposes of illustration,
FIGS. 1 and 2
show schematic representations of examples of air moving systems that include multiple air movers.
Referring first to
FIG. 1
, an air moving system (generally designated by the numeral “
10
”) is intended to dissipate heat that is generated within an enclosure
12
such as a cabinet, chassis, housing or other structure. The enclosure
12
has an interior
14
in which an electronic system can be mounted. Enclosure
12
also has one or more openings such as an opening
16
for intake air flow as well as a pair of openings
18
a
and
18
b
for exhaust air flow. Air movers (not shown) are oriented to urge air flow through opening
16
, into interior
14
, and out to the exterior of enclosure
12
through openings
18
a
and
18
b
. More specifically, intake air flow “A” is urged into opening
16
and exhaust air flow “B
1
” and “B
2
” is urged outwardly through openings
18
a
and
18
b
, respectively. Air is therefore caused to flow along primary air flow paths
20
a
and
20
b
, which are shown in
FIG. 1
as dotted lines extending from opening
16
to openings
18
a
and
18
b.
Although not shown in
FIG. 1
, it will be understood that an air mover is positioned anywhere along each of the primary air flow paths
20
a
and
20
b
in order to urge air flow along the respective paths. For example, an air mover can be positioned within interior
14
proximal to each opening
18
a
and
18
b
, near opening
16
, or anywhere in the space between opening
16
and
18
a
or
18
b
. These air movers cooperate to generate intake air flow A by producing a low pressure zone within interior
14
of enclosure
12
, thereby drawing air into the enclosure and then forcing air outwardly in the form of exhaust air flow B
1
and B
2
.
It has been discovered that the failure of an air mover can result in reverse air flow through the exhaust openings and that such reverse air flow can change the air flow pattern detrimentally and reduce the cooling air flow that is directed across the heat-generating components of the electronic system. For example, if an air mover positioned along primary air flow path
20
a
fails, exhaust air flow B
1
will be replaced by reverse air flow “C
1
” through opening
18
a
due to the low pressure zone within interior
14
. Similarly, failure of an air mover oriented along primary air flow path
20
b
would result in the replacement of exhaust air flow B
2
with reverse air flow “C
2
” through opening
18
b
. A failure of an air mover oriented along primary air flow paths
20
a
or
20
b
would therefore tend to result in air flow along a secondary air flow path
20
c
between openings
18
a
and
18
b
. For example, if an air mover positioned along primary air flow path
20
a
were to fail, then reverse air flow C
1
through opening
18
a
would travel along secondary air flow path
20
c
to opening
18
b
. Such a change in the air flow pattern reduces the flow of air across the heat-generating electronic components and also re-directs air flow away from portions of the interior
14
of enclosure
12
.
Referring now to
FIG. 2
, an air mover system
30
also includes an enclosure
32
with an interior
34
, as well as openings
36
for exhaust air flow and
38
a
and
38
b
for intake air flow. The air mover system
30
in
FIG. 2
differs from the one illustrated in
FIG. 1
because it is adapted for the use of air movers (not shown) that are positioned proximal to openings
38
a
and
38
b
to urge intake air flow A
1
and A
2
into interior
34
and out from interior
34
as exhaust air flow B by creating a high pressure zone within interior
34
. Accordingly, air movers positioned along primary air flow paths
40
a
and
40
b
urge air through the interior
34
from openings
38
a
and
38
b
to opening
36
. Failure of an air mover therefore would result in reverse air flow C
1
or C
2
as well as air flow along a secondary air flow path
40
c.
As illustrated in
FIGS. 1 and 2
, it has been discovered that the failure of an air mover in an air moving system that utilizes multiple air movers can compromise the cooling effect significantly. Not only does such a failure reduce the intake and exhaust air flow by eliminating the contribution of the failed air mover, but such a failure also results in a detrimental change in the air flow pattern and air flow rate within the enclosure from which heat is being dissipated.
Attempts have been made in the past in order to overcome this problem. For example, U.S. Pat. No. 5,438,226, issued to Douglas A. Kuchta, describes the use of louvers that can be added to a fan assembly in order to prevent backwards flow of air through the opening of a failed fan. The Kuchta patent also discloses the arrangement of air movers in series with respect to the air flow as opposed to banked designs which arrange fans in parallel with the air flow. The series air moving system proposed by the Kuchta patent is intended to reduce hot spots which may result when one fan in a parallel fan bank fails and to reduce backward air flow through a failing air mover because the remaining air mover in series establishes flow in the proper direction.
Nevertheless, there remains a need for an improved air mover system that is capable of reducing reverse air flow in the event that one or more of multiple air movers fails.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned objectives and to overcome the disadvantages associated with conventional air mover systems, this invention provides a system adapted for generating air flow using multiple air movers. Each of the air movers is mounted along a desired air flow path.
Each air mover includes means mounted for rotation to generate forward air flow along an air flow path. Each air mover also has means for preventing reverse rotation, thereby reducing reverse air flow along the air flow path.
The air movers can include an impeller or a fan blade or other rotating means for generating air flow. A breaking arm, one-way bearing or other means for preventing reverse rotation can be mounted so that it is capable of permitting forward rotation while preventing reverse rotatio
Smith Grant M.
Wessel Mark William
Adornato Rocco L.
Joyce Harold
Ratner & Prestia
Starr Mark T.
Unisys Corporation
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