Acoustic cooling system with noise reduction function

Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – From appliance

Reexamination Certificate

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Details

C381S071100, C381S071110

Reexamination Certificate

active

06625285

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an acoustic cooling system which cools a cooling object making use of an endothermic action when desired coolant in the form of gas, liquid or the like contained in a vessel expands after a sound wave (acoustic oscillatory wave) is forwarded into the vessel to compress the coolant in the vessel, and more particularly to an acoustic cooling system with a noise reduction function by which noise produced when a sound wave is forwarded into a vessel can be reduced.
2. Description of the Related Art
FIG. 9
is a perspective view schematically showing an example of an appearance of a typical acoustic cooling system, and
FIG. 10
is a diagrammatic view schematically showing a construction of part of the acoustic cooling system shown in FIG.
9
. Referring to
FIGS. 9 and 10
, the acoustic cooling system
100
shown includes an acoustic compressor
110
, a condenser
120
, a carburetor
130
, an oscillation circuit
140
and a control circuit
180
. The acoustic compressor
110
and the condenser
120
are connected to each other by a discharge pipe
150
, and the acoustic compressor
110
and the carburetor
130
are connected to each other by a suction pipe
160
. Further, an exit
121
of the condenser
120
and an entrance
131
of the carburetor
130
are connected to each other by a capillary tube
170
.
The acoustic compressor
110
compresses desired coolant such as, for example, freon gas for cooling a cooling object such as, for example, air in a refrigerator making use of a sound wave (acoustic oscillatory wave). The acoustic compressor
110
includes, as seen in
FIG. 10
, a tubular chamber (vessel)
111
in which the coolant is contained, and an acoustic driver (sound source)
112
provided adjacent an opening
115
of the chamber
111
for forwarding a sound wave into the chamber
111
. The acoustic driver
112
is driven with a predetermined frequency by the oscillation circuit
140
so that it forwards a sound wave of a predetermined wavelength into the chamber
111
to produce an acoustic standing wave in the chamber
111
to compress the coolant.
The acoustic driver
112
is controlled by the control circuit
180
so that the sound pressure of a sound wave to be forwarded may be optimized to keep the temperature and the pressure of the coolant at respective predetermined optimum values. The function just described is realized, for example, by supervising the temperature and the pressure of the coolant which is in the chamber
111
or which passes through a pipe which forms the condenser
120
using temperature and pressure sensors or like devices.
The chamber
111
has a length L set to 3&lgr;/4 (where &lgr; is the wavelength of a sound wave forwarded from the acoustic driver
112
) so that one pressure node
117
and one pressure antinode
118
of a standing wave may be produced in the chamber
111
as seen in FIG.
10
.
The chamber
111
has a discharge chamber
113
and a suction chamber
114
provided at locations on a curved face thereof which correspond to the positions at which the pressure node
117
and the pressure antinode
118
are produced. The discharge chamber
113
is provided for communication with the chamber
111
through a discharge valve
113
a
, and the suction chamber
114
is provided for communication with the chamber
111
through a suction valve
114
a
. If the pressure around the pressure node
117
becomes higher than a predetermined value, then the discharge valve
113
a
is opened to allow the compressed coolant to be discharged into the discharge pipe
150
through the discharge chamber
113
. When the pressure around the pressure antinode
118
becomes lower than a predetermined value as a result of the discharging operation, the suction valve
114
a
is opened to allow the coolant, which has circulated through the condenser
120
and the carburetor
130
, to be sucked into the chamber
111
through the suction chamber
114
.
The condenser
120
radiates heat of the coolant, which is compressed by the acoustic compressor
110
and flows as gas of a high temperature and a high pressure into the condenser
120
through the discharge pipe
150
, to the outside to condense the coolant into coolant of a room temperature and a high pressure in the form of liquid. The capillary tube
170
reduces the pressure of the coolant of a room temperature and a high pressure in the form of liquid by the flow resistance thereof. If the pressure of the liquid coolant is reduced lower than a certain fixed value by the flow resistance, then the liquid coolant begins to partially vaporize (evaporate) and enter into a low temperature, low pressure state.
The carburetor
130
fully vaporizes (expands) the liquid coolant, which has begun to partially vaporize and flows into the carburetor
130
through the capillary tube
170
, into high temperature, high pressure gas, whereupon the carburetor
130
derives heat necessary for such vaporization from a cooling object such as, for example, air in a cooling space
132
of the refrigerator to cool the cooling object. It is to be noted that the coolant (gas) of a high temperature and a low pressure which has derived heat from the cooling object in this manner is sucked into the acoustic compressor
110
through the suction pipe
160
and the suction chamber
114
and compressed again by the acoustic compressor
110
, and consequently, it is discharged as high temperature, high pressure coolant into the condenser
120
through the discharge pipe
150
.
In the typical acoustic cooling system
100
having such a construction as described above, when the acoustic driver
112
is driven by the oscillation circuit
140
first, a sound wave having, for example, a wavelength &lgr; is forwarded into the chamber
111
. Consequently, the sound wave (progressive wave) is reflected in a condition displaced by
180
degrees in phase by a face of an end wall
116
of the chamber
111
. Since the length L of the chamber
111
is 3&lgr;/4, the reflected wave resonates with the progressive wave from the acoustic driver
112
to form an acoustic standing wave which has a pressure node
117
and a pressure antinode
118
.
In this condition, if the control circuit
180
controls the sound pressure of the sound wave to be forwarded from the acoustic driver
112
so that the pressure around the pressure node
117
may be higher than the predetermined value, then the discharge valve
113
a
is opened. Consequently, the compressed coolant (gas) of a high temperature and a high voltage is discharged into the discharge pipe
150
through the discharge chamber
113
. The coolant is then forwarded into the condenser
120
through the discharge pipe
150
, and in the condenser
120
, the coolant discharges its heat to the outside (into the air). Consequently, the coolant changes into coolant of a low temperature and a high pressure in the form of liquid.
Then, the liquid coolant is forwarded into the carburetor
130
through the capillary tube
170
. When the liquid coolant passes the capillary tube
170
, the pressure thereof is reduced by the flow resistance of the capillary tube
170
and the liquid coolant partially begins to vaporize (becomes coolant of a low temperature and a low pressure). When the liquid coolant which has begun to partially vaporize flows into the carburetor
130
from the capillary tube
170
, it derives heat from the cooling object (air) in the cooling space
132
, whereupon it is vaporized fully (becomes coolant of a high temperature and a low pressure).
The coolant which has derived heat from the cooling object in this manner is forwarded into the suction chamber
114
of the acoustic compressor
110
through the suction pipe
160
. Then, the coolant is sucked into the chamber
111
from the suction chamber
114
as the suction valve
114
a
is opened when compressed coolant is discharged through the discharge chamber
113
until the pressure around the pressure antinode
118
in the chamber
111
becomes lower than the predetermined v

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