Rotary kinetic fluid motors or pumps – With sound or vibratory wave absorbing or preventing means...
Reexamination Certificate
1999-01-19
2001-07-03
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With sound or vibratory wave absorbing or preventing means...
C415S204000, C415S206000, C415S207000, C415S212100
Reexamination Certificate
active
06254336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sirocco fan, and more particularly, to a cutoff which divides an inlet and outlet side of the sirocco fan.
2. Discussion of the Related Art
Generally, a sirocco fan is kind of blower which is used for air-conditioning and ventilating, and is used in an air-conditioner or fan-coil heater. Also, the sirocco fan is called a multi-blade fan because it has about 30 to 50 blades. In this respect, the sirocco fan is compared differently with the radial fan having blades smaller than those of the sirocco fan.
FIGS. 1 and 2
are perspective and side views illustrating a related art sirocco fan.
The related art sirocco fan will be described with reference to
FIGS. 1 and 2
.
The sirocco fan
1
includes a scroll
2
which acts as air passage, and an impeller
3
which is provided in the scroll
2
and used for inlet and outlet of the air by the driving force of a motor (not shown).
The impeller
3
includes a pair of rims
3
a
and a plurality of blades
10
which are parallel to the rims
3
a.
The scroll
2
is divided into a circular main body
2
a
where the impeller
3
is located and a diffuser
20
connected with the main body
2
a
. And the main body
2
a
includes an inlet wall
8
having an inlet
4
and a closed endwall
9
which is opposed to the inlet wall
8
. A front end of the diffuser
20
acts as an outlet
5
.
Therefore, in the sirocco fan
1
, the air is sucked from the inlet
4
at the inlet wall
8
of the scroll
2
and exhausted out through the outlet
5
of the diffuser
20
.
A reference numeral
6
which is not described is a bell-mouth which is located at the inlet
4
and fitted into the scroll
2
to guide sucking air and at the same time to shield the impeller
3
.
In addition, the starting point in the diffuser
20
of the scroll
2
is a cutoff
7
. The cutoff
7
is the standard point of the expansion radius of the scroll
2
and the important part to divide the inlet and outlet side.
In other words, since the cutoff
7
is the starting point which changes dynamic pressure into static pressure, it acts as the starting point of air outlet and quick change of pressure periodically occurs therein.
As shown in
FIG. 2
b
, in the related art sirocco fan
1
, the cutoff
7
is parallel to the blade
10
of the impeller
3
or it is tapered at about 2° or less so as to easily separate the scroll
2
from the mold when producing the scroll
2
.
Referring to
FIGS. 2
a
and
2
b
, the operation of the related art sirocco fan will be described below.
Once the impeller
3
which is located in the scroll
2
is rotated by the driving force of the motor, suction power occurs by the rotation of the impeller
3
, so that the air is sucked into the scroll
2
through the inlet
4
formed in the inlet wall
8
of the scroll
2
. The sucked air is exhausted out of the scroll
2
through the outlet
5
formed in the scroll
2
while flowing inside the scroll
2
by the continuous rotation of the impeller
3
.
However, the related art sirocco fan has the following problems.
First, since the cutoff
7
is parallel to the blade
10
of the impeller, abnormal noise occurs significantly due to the blade passing frequency (BPF). The reason is, when the blade
10
of the impeller
3
meets the cutoff
7
by the rotation of the impeller
3
, the blade
10
is parallel to the cutoff
7
and at the same time the entire sections of the blade
10
meet the entire sections of the cuttoff
7
so that there occurs abnormal noise due to the BPF in the entire length direction of the blade.
Second, as shown in the
FIG. 3
, the speed of the incoming air does not decrease until it hits the endwall
9
of the sirocco fan
1
. Therefore the incoming air retains the axial speed component until the time it passes through the blade
10
of the impeller
3
. For this reason, the air that has hit the endwall
9
is re-circulated along the side of the scroll
2
.
Also, since the scroll
2
cannot transfer the dynamic pressure into static pressure, the flow speed of the point close to the endwall
9
at the outlet
9
is comparatively fast and at the inlet wall
8
the flow speed is rather slow, thereby causing flow of the exhausting air to be irregular. Moreover, counterflow A may sometimes occur.
In summary, in the related art sirocco far, there is a problem that the air flow is poor due to abnormal noise.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a sirocco fan that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a sirocco fan which reduces abnormal noise due to the BPF.
Other object of the present invention is to a sirocco fan which increases air flow rate and enables stable air flow.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a sirocco fan according to the present invention includes: a scroll with an inlet wall and a closed endwall, the inlet wall having an inlet and the endwall being opposed to the inlet wall; and an impeller provided in the scroll, for suctioning and exhausting air, wherein a cutoff of the sirocco fan is inclined so as not to allow entire sections of the blade of the impeller to be simultaneously met entire sections of the cutoff when the blade of the impeller passes through the cutoff, thereby achieving stable air flow.
It is preferable that the cutoff is inclined towards the endwall from the inlet wall of the scroll and it may have a straight lined shape or a curved shape. Also, the cutoff has preferably an inclined angle in the range of 20° between 50°, more preferably in the range of 30° between 40°. Therefore, the sirocco fan of the present invention can reduce abnormal noise and also achieve high air flow rate and stability of air flow.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 353994 (1886-12-01), Walker et al.
patent: 3687360 (1972-08-01), Prew et al.
patent: 1100399 (1989-04-01), None
W. Neise, “Noise Reduction In Centrifugal Fans: A Literature Survey”, Journal Sound and Vibration (1976), 45(3), 375-403.
LG Electronics Inc.
Look Edward K.
Nguyen Ninh
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