Stoves and furnaces – Hot-air furnaces – Liquid or gaseous fuel
Reexamination Certificate
2000-02-25
2002-06-11
Clarke, Sara (Department: 3743)
Stoves and furnaces
Hot-air furnaces
Liquid or gaseous fuel
C431S020000
Reexamination Certificate
active
06401708
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas furnace, and more particularly, to a device for sensing an internal pressure difference of a gas furnace, and a method for controlling operation of the gas furnace by using a pressure sensing device.
2. Background of the Related Art
In general, the gas furnace is a device which alters cold air into a warm air by a heat exchange using a heat from combustion of gas, and heats a room by using the warm air. A basic structure of such a gas furnace is shown in
FIG. 1
, referring to which the gas furnace will be explained. There is an air inlet
2
at a lower portion of a front surface of a body
1
for drawing cold air in the room, and an air outlet
4
at an upper portion of the front surface of the body
1
for discharging the air heat exchanged in the gas furnace. And, there is a partition
15
having an opening between opposite sidewalls of the body
1
to divide an inside cavity of the body
1
, a combustion chamber
6
over the partition for burning the gas, and a housing
2
under the partition having a blower
3
mounted therein. There is a burner
7
in the combustion chamber
6
connected to a gas supply tube
8
for mixing air and gas, and igniting the mixed gas for producing flame, and a gas shut off valve between the gas supply tube
8
and the burner
7
for selective shut off of the gas supply. And, there is a heat exchanger
13
over the combustion chamber for altering a cold air drawn inside of the body
1
by movement of exhaust gas into warm air. There is an exhaust gas pipe
14
connected to the heat exchanger
13
for discharging the exhaust gas heat exchanged with the cold air, and an air supply pipe
9
to the burner
7
for supplying fresh air required for combustion. And, there is an air supply fan
11
connected to the air supply pipe for supplying the fresh air to the burner
7
. There is a space at one side of the upper portion of the partition
15
for mounting various parts including a controller
16
, and a barrier
5
for supporting the parts. Such a gas furnace conducts a pre-purge when the gas furnace is put into operation, in which a fresh air from the air supply fan
11
is passed through the combustion chamber
6
, the heat exchanger
13
and the exhaust gas pipe
14
for a few minutes without burning the gas for driving out unburned gas remained in the combustion chamber
6
and etc. After the pre-purge process is finished, an actual combustion is started in the combustion chamber
6
, and the fresh air introduced from outside of the gas furnace by the air supply fan
3
is heated as the air passes through the combustion chamber
7
and the heat exchanger
13
. Finally, the heated air is supplied to the room through a discharge hole
10
, and the gas furnace keeps supplying the heated air until a preset temperature is reached. In this instance, the pre-purge is carried out as the air supply fan
11
is operated by the controller
16
, and, after the pre-purge is finished, the combustion is carried out as the gas valve
12
is opened by the controller
16
. However, in using the related art gas furnace, there are cases in actual operation of the gas furnace when the air supply pipe or the exhaust gas pipe are clogged from various reasons, that impedes normal operation of the gas furnace. That is, if a combustion process is conducted in a state the air supply pipe
9
or the exhaust gas pipe is clogged, the mixed gas is burned in the combustion chamber incompletely because fresh air supply to the combustion chamber is reduced significantly in comparison to the gas supply. This incomplete combustion may cause explosion of the unburned gas in the combustion chamber
6
, pollution of an environment, or inflow of the unburned gas into the room.
In the meantime, in order to solve this problem, the applicant filed a patent, Korea Patent application No. 98-38517, titled “device and method for sensing an air pressure in a gas furnace”, of which systems are shown in
FIGS. 2A and 2B
, schematically. The application suggests to provide an air pressure sensing switch for sensing a supply side pressure either on an inlet side or an outlet side with reference to the air supply fan
11
, for sensing clogging of the air supply pipe
9
and the exhaust gas pipe
14
according to a difference of the air pressure sensed by the air pressure sensing switch and the atmospheric pressure. In detail, as shown in
FIG. 2A
, in a first embodiment of the Korea patent application No. 98-38517, a first air opening of the air pressure sensing switch is connected to the air supply pipe on the inlet side of the air supply fan
11
, and the second air opening is opened to the air. And, as shown in
FIG. 2B
, in a second embodiment of the Korea patent application No. 98-38517, the first air opening of the air pressure sensing switch is opened to the air, and the second air opening is connected to the air supply pipe on the outlet side of the air supply fan
11
. In the foregoing embodiments of the Korea patent application No. 98-38517, the air pressure switch generates a signal only when a pressure difference(&Dgr;P=a second air opening pressure—a first air opening pressure) between the second air opening pressure and the first air opening pressure is increased.
In the meantime, when it is assumed that an inlet side pressure is P
1
and an outlet side pressure is P
2
with reference to the air supply fan
11
, the pressures P
1
and P
2
are the first air opening pressure and the second air opening pressure, respectively. And, both pressures P
1
and P
2
are reduced when the air supply pipe
9
is clogged, and increased when the gas exhaust pipe
14
is clogged. However, as explained, while the air pressure switch generates the signal only when the pressure difference is increased, and the pressure difference of the air pressure switch is reduced sometimes depending on conditions, such as clogging of the air supply pipe
9
or clogging of the exhaust gas pipe
14
. That is, when the gas exhaust pipe
14
is clogged in the first embodiment, a pressure difference(&Dgr;P=P
2
-atmospheric pressure) of the air pressure switch is dropped as an outlet pressure P
2
of the air supply fan
11
is dropped. Therefore, in the invention disclosed by the Korea patent No. 98-38517, clogging of the air supply pipe
9
only is sensed when the air pressure sensing switch is fitted to the inlet side of the air supply fan
11
of the air supply pipe
9
, and clogging of the exhaust gas pipe
14
only is sensed when the air pressure sensing switch is fitted to the outlet side of the air supply fan
11
. Accordingly, there has been a problem in that both clogging of the air supply pipe
9
and clogging of the exhaust gas pipe
14
can not be sensed by using one air pressure sensing switch. Though the air pressure sensing switches may be fitted to both the inlet side and the outlet side of the air supply fan
11
, the increased number of the air pressure sensing switches leads to an increased production cost and a complicated structure.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a device for sensing an internal pressure difference of the gas furnace, and a method for controlling operation of a gas furnace by using a pressure sensing device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
The object of the present invention is to provide a device for sensing a pressure in a gas furnace, and a method for controlling operation of a gas furnace by using a pressure sensing device, which can detect both clogging of an air supply pipe and clogging of an exhaust air pipe.
Other object of the present invention is to provide a device for sensing a pressure which costs low and has a simple structure.
Another object of the present invention is to provide a method for controlling operation of a gas furnace by using a pressure sensing device which can sense clogging both of air supply pipe and an exhaust gas pipe.
Kim In Kyu
Kim Kyeong Soo
Kim Yang Ho
Kim Yeong Soo
Clarke Sara
Fleshner & Kim LLP
LG Electronics Inc.
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