U.S. patent application number 10/638585 was filed with the patent office on 2005-02-17 for time-extended cooling system for line-powered apparatus.
Invention is credited to Dietz, Paul H., Leigh, Darren L..
Application Number | 20050034468 10/638585 |
Document ID | / |
Family ID | 34135692 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050034468 |
Kind Code |
A1 |
Dietz, Paul H. ; et
al. |
February 17, 2005 |
Time-extended cooling system for line-powered apparatus
Abstract
Certain electrical systems, such as projectors, contain
components, which get very hot and require active cooling systems.
During normal operation, a switch operates a cooling fan from a
primary power supply. Upon detecting a failure in the primary power
supply, the switch connects the cooling fan to a secondary power
supply.
Inventors: |
Dietz, Paul H.; (Hopkinton,
MA) ; Leigh, Darren L.; (Belmont, MA) |
Correspondence
Address: |
Patent Department
Mitsubishi Electric Research Laboratories, Inc.
201 Broadway
Cambridge
MA
02139
US
|
Family ID: |
34135692 |
Appl. No.: |
10/638585 |
Filed: |
August 11, 2003 |
Current U.S.
Class: |
62/236 |
Current CPC
Class: |
F21V 29/67 20150115;
F25B 21/02 20130101; F25B 27/00 20130101; H04N 9/3144 20130101;
F25D 2700/16 20130101; F21V 29/56 20150115 |
Class at
Publication: |
062/236 |
International
Class: |
F25B 027/00 |
Claims
We claim:
1. A time-extended cooling apparatus, comprising: means for
cooling; a primary power supply connected to the means for cooling;
a secondary power supply connected to the means for cooling; means
for operating the means for cooling from the primary power supply;
means for sensing a failure in the primary power supply; and means
for switching the means for cooling to the secondary power supply
in response to sensing the failure in the primary power supply.
2. The apparatus of claim 1 wherein the means for cooling is a
fan.
3. The apparatus of claim 1 wherein the means for cooling is a
liquid cooling system.
4. The apparatus of claim 1 wherein the means for cooling is a
Peltier device.
5. The apparatus of claim 1 wherein the means for cooling is a
refrigeration system.
6. The apparatus of claim 1 further comprising: a projector lamp
generating heat.
7. The apparatus of claim 1 wherein the secondary power supply is a
rechargeable battery.
8. The apparatus of claim 1 wherein the secondary power supply,
means for operating, means for sensing, and means for switching are
embedded in the means for cooling.
9. The apparatus of claim 1 wherein the secondary power supply is a
spring.
10. The apparatus of claim 1 wherein the secondary power supply is
a capacitor.
11. The apparatus of claim 1 wherein the means for operating
maximizes a time the means for cooling operates.
12. The apparatus of claim 1 further comprising: means for sensing
a temperature of a component cooled by the means for cooling.
13. The apparatus of claim 1 further comprising: a heat sensitive
device; means for sensing a temperature of the heat sensitive
device; and means for operating the means for cooling from the
secondary power supply until the heat sensitive device reaches a
predetermine reduced temperature.
14. The apparatus of claim 13 wherein the heat sensitive device is
a projector lamp.
15. A time-extended cooling apparatus, comprising: means for
cooling mounted in close proximity to a lamp in a projector; a
primary power supply connected to the means for cooling; a
secondary power supply connected to the means for cooling; means
for operating the means for cooling from the primary power supply;
means for sensing a failure in the primary power supply; means for
sensing a temperature of the lamp; and means for switching the
means for cooling to the secondary power supply in response to
sensing the failure in the primary power supply until the lamp
reaches a predetermined reduced temperature.
16. A method for time-extended cooling, comprising: operating a
cooling system from a primary power supply; sensing a failure in
the primary power supply; and operating the cooling system from a
secondary power supply in response to sensing the failure in the
primary power supply.
17. The method of claim 15 further comprising: sensing a
temperature of a heat sensitive device; and operating the cooling
system from a secondary power supply until the heat sensitive
device reaches a predetermined reduced temperature.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to cooling systems,
and more particularly to line-powered electrical devices that
generate heat.
BACKGROUND OF THE INVENTION
[0002] Many electrical devices and systems require active cooling
systems to prevent over-heating. In passive cooling systems, the
heat generated from internal components is conducted away to a
cooler area via a path of sufficiently low thermal resistance. If
the thermal resistance is too high or if the temperature difference
is too small to support sufficient heat flow, active cooling
systems must be employed. Forced air-cooling is often used for this
purpose. It effectively lowers the thermal resistance, and thus
lowers the temperature rise with respect to ambient conditions for
a given amount of thermal energy.
[0003] In some systems, the heat generating components can get
extremely hot. The temperature inside the component is often
sufficient to destroy neighboring parts, unless the components are
cooled. For example, the temperature inside a video projector bulb
can exceed several thousand degrees. Damage is prevented by keeping
the thermal resistance from those surrounding areas to the ambient
air as low as possible compared to the thermal resistance from the
heat source to the surrounding areas. In effect, the very high
temperatures are contained in a small area through this thermal
resistance mismatch. Often, a fan or other cooling device is
employed to keep the outer thermal resistance as low as
possible.
[0004] It is useful to consider what happens when line-power is
suddenly lost in actively cooled equipment with a high temperature
component. Although no further heat is generated in the component,
the thermal mass of the component has stored some amount of heat
energy, which must be dissipated. Thus, heat continues to flow out
of the component. If an active cooling system ceases to function,
the outer thermal resistance increases, slowing the flow of heat to
the ambient environment, and in effect, creating an outer, somewhat
more thermally insulated layer. This can cause a dramatic
temperature rise in the parts surrounding the hot component, which
can be destructive.
[0005] To combat this problem, many electronic systems with hot
components have a special power-down cycle, which immediately
removes power from the heat-generating component, but continues to
run the cooling system for sufficient time to cool down the hot
component. A severe problem arises if all power is lost
unexpectedly, and a normal cool down cycle is not possible. For
video projectors, sudden loss of power and the resulting inability
to properly cool the lamp results in a premature device failure.
There is a clear need for a method of cooling devices and systems
in a controlled manner, even in the event of the loss of line
power.
[0006] A similar thermal problem occurs in an internal combustion
engine, where heat must be dissipated after the engine has been
turned off. U.S. Pat. No. 5,828,967 describes a method of using a
by-pass line to continue to run the cooling fan for some time after
the engine is turned off. In this case, the fan power comes
typically from a battery. Because the battery is needed to start
the engine, the amount of energy that is used for running the fan
after shutdown is minimized.
[0007] U.S. Pat. No. 6,472,828 describes a method for controlling
fan speed in a projector in order to allow faster bulb turn-on. By
running the fan at low speeds initially, the thermal resistance is
momentarily higher, allowing the temperature to rise rapidly. The
fan speed is then increased to prevent overheating during normal
operation. However, the system does not address cool down in the
event of line power loss.
[0008] U.S. Pat. No. 5,938,407 addresses an entirely different
problem. There, it is desired to keep a coal stove fire as hot as
possible in the event of a primary power loss. That system includes
two motors that run a fan. The backup motor mechanically engages
with the fan, and an alternate power source controlled by a backup
circuit. When power is lost, a solenoid is de-energized, depressing
a switch and completing the backup circuit to the alternate power
source. The backup motor rotates into contact with the fan to
ensure uninterrupted airflow. That backup system is for powering an
air distribution fan that ensures sufficient oxygen reaches a coal
fire burning within a coal stove to maintain the coal fire hot
until primary power is restored.
[0009] Many clocks have a battery-backup feature. In this case,
time keeping is the issue rather than thermal concerns. Similarly,
backup generators and uninterruptible power supplies are commonly
used to keep computers and other vital equipment running during a
power failure.
[0010] Various thermal fuses and other protection devices exist
which cut power to equipment when excessive temperatures are
detected. They do not function in the event of a power failure.
SUMMARY OF THE INVENTION
[0011] It is an objective of the present invention to provide
cooling to high temperature components in electronic equipment in
the event of the loss of line power.
[0012] It is another objective of the invention to prevent damage
to electrical equipment in the event of the loss of line power as
caused by the stored heat of certain high temperature
components.
[0013] The electrical equipment containing the invention is
provided with an energy storage device. This energy storage device
receives and stores energy during normal line-powered operation.
When line power is lost, the energy storage device provides power
to operate an active cooling system for a period of time sufficient
to prevent thermal damage.
[0014] The energy storage device can take one or more forms,
including, but not limited to the following: a battery, a
capacitor, a spring, a flywheel, a compressed gas, and the
like.
[0015] The cooling system can take one or more of a plurality of
forms, including, but not limited to the following: a fan, a liquid
cooling system, a Peltier device, a refrigeration system, and the
like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram of a system using a time-extended
cooling apparatus according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] FIG. 1 shows a projector system 100 that uses the invention.
It should be understood that the invention can also be used by
other heat generating electrical systems and devices.
[0018] The projector includes a heat source 110, i.e., a lamp. The
temperature of the lamp can reach several thousand degrees. If the
lamp gets too hot, then it can self-destruct, as well as damage
nearby components. Therefore, during normal operation, a fan 120 is
used to cool the lamp. The fan is connected to a primary power
supply 130, normally a power line.
[0019] In most modern projectors, the fan will continue to run for
several minutes after the projector has been shut off to cool the
lamp. However, should there be a failure in the power line, damage
can still occur.
[0020] Therefore, the projector 100 also includes a secondary power
supply 140, for example, a rechargeable battery. Should there be a
failure in the primary power supply, then a switch 150 can cause
the fan 120 to be operated from the secondary power supply until a
sensor 160 determines that the lamp has cooled sufficiently. The
sensor can also control the speed of the fan to maximize battery
lifetime.
[0021] In the preferred embodiment, the rechargeable battery is
contained in an accessible compartment 170. The switch or another
simple sensor determines the presence or absence of the battery. If
the battery is not installed, or the battery is low in charge, an
audible or visual warning can be given. Alternatively, a network
can be used to send an alert message to a system operator.
[0022] An alternative embodiment of the invention embeds the
secondary power supply, sensor and switch in the fan. A fan thus
configured can be installed in any place where time-extended
cooling is required.
[0023] It is possible to use mechanical energy storage devices to
the same effect. In another alternative embodiment, the fan is
modified to wind a clock spring to a certain tension and maintain
it at a given level. When primary power is removed, the spring
provides the power to spin the fan for some additional time.
[0024] Although the invention has been described by way of examples
of preferred embodiments, it is to be understood that various other
adaptations and modifications may be made within the spirit and
scope of the invention. Therefore, it is the object of the appended
claims to cover all such variations and modifications.
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