Centrifugal blower

Details Centrifugal blower Centrifugal blower

1999-12-02

2001-08-14

Ryznic, John E. (Department: 3745)

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Casing having tangential inlet or outlet

C415S207000

Reexamination Certificate

active

06273679

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a centrifugal blower, and more particularly to a scroll casing of a centrifugal blower.
2. Description of the Prior Art
As illustrated in
FIG. 1
, a centrifugal blower according to the prior art includes a siroco fan
2
having a plurality of fins in peripheral directions, and a scroll casing spirally forming a draft passage at an external side of the siroco fan
2
, where air is infused along an axle direction of the siroco fan
2
to form an eddy current in the scroll casing at a 90 degree direction relative to an air intake, to thereby be discharged via a discharge outlet
6
.
A spiral of the scroll casing in the conventional centrifugal blower consists of an Archimedean spiral and a logarithmic spiral, where a spiral start point (P
1
) is situated at an inner side of a spiral chamber (S) from a line connecting a center (O) of the siroco fan
2
and a spiral end point (F
1
), such that a scroll angle is over 360 degrees.
Furthermore, as illustrated in
FIG. 2
, the Archimedean spiral is a curved line where a scroll radius (a distance from a center of an siroco fan to a spiral) is linearly increased as a scroll angle (an angle measured from a spiral start point to a spiral end point) is increased, and the logarithmic spiral is a curved line where a scroll radius is linearly and almost straightly increased as a scroll angle is increased.
There is a problem however in that a scroll casing manufactured by utilizing the Archimedean spiral or the logarithmic spiral can easily form a curved line and is easy in manufacturing but eddy current is dispersed at a certain range of a peripheral direction to thereby reduce a blowing efficiency such that performance of a blower is decreased to thereby increase a noise.
In order to complement those problems at the scroll casing manufactured by using the Archimedean spiral or the logarithmic spiral, Japanese laid-open patent No. Hei 6-117397 is disclosed where a spiral is correctively manufactured to have a non-linear shape.
As illustrated in
FIG. 3
, a spiral of a scroll casing
14
in the Japanese laid-open patent No. Hei 6-117397 constitutes a scroll radius formed in a certain expanded angle from a spiral start point (P
2
) to an optional scroll angle, (&thgr;
1
) where a scroll radius from the scroll angle (&thgr;
1
) to a spiral end point (F
2
) is greater than a scroll radius formed in a predetermined expanded angle from the spiral start point (P
2
) to the spiral end point (F
2
), and a scroll radius of the spiral end point (F
2
) is the same as a scroll radius formed in a predetermined expanded angle from the spiral start point (P
2
) to the spiral end point (F
2
).
In other words, as illustrated in
FIG. 4
, when a scroll angle of the spiral start point (P
2
) is given as O and a scroll angle of the spiral end point (F
2
) is given as &thgr;
2
, a scroll radius of spiral at a scroll casing
14
can be described in the following formula.
r(&thgr;)=r
0
+r
1
exp(n&thgr;)+R(&thgr;),
where
R(&thgr;)=0 in case of 0<&thgr;<&thgr;
1,
and
R(&thgr;)=K
1
sin{&pgr;/2×(&thgr;−&thgr;
1
)/(&thgr;−&thgr;
2
)} in case of &thgr;
1
<&thgr;<&thgr;
2
,
and where
r
0
=distance between a peripheral surface of an siroco fan and spiral start point (P
2
), r
1
=siroco fan radius, n=expanded angle and &thgr;=a voluntary angle measured on the spiral start point (P
2
).
A solid line in
FIG. 4
represents a scroll radius formed in a predetermined expanded angle from the spiral start point (P
2
) to the spiral end point (F
2
), and a dotted line defines a scroll radius from the voluntary scroll angle (&thgr;
1
) to the scroll angle (&thgr;
2
) at the spiral end point. Furthermore, the spiral start point (P
2
) moves towards external side of the spiral chamber (S) on a line connecting the center (
0
) of the siroco fan
12
to the spiral end point (F
2
). The range of the scroll angle is below 360 degrees.
However, there is a problem in the scroll casing according to the Japanese laid open patent No. Hei 6-117397 in that it is very difficult to manufacture same in accurate non-linear curve according to the numerical formula. There is another problem in that frictional resistance between airs and between inner surfaces of scroll casing is not much reduced to decrease a blowing efficiency and performances of a blower and to thereby increase a noise.
SUMMARY OF THE INVENTION
The present invention is disclosed to solve the aforementioned problems and it is an object of the present invention to provide a centrifugal blower capable of being easily manufactured and having a higher blowing efficiency but with less noise.
In accordance with the object of the present invention, there is provided a centrifugal blower, the blower comprising:
a siroco fan having a plurality of blowing fans; and
a scroll casing forming a spiral draft passage at an external side of the siroco fan, where, the siroco fan is so mounted as to allow centre of the siroco fan to be detached at a predetermined distance from centre of a spiral comprising the draft passage of the scroll casing.
The spiral of the scroll casing is an Archimedean spiral or an logarithmic spiral.
A scroll start point and scroll end point of the scroll casing are situated on a same line, such that a scroll angle varies from zero (0) degree to 360 degrees but the scroll angle can be ranged below 360 degrees or above 360 degrees.
The centre of the siroco fan is moved from a spiral centre of the scroll casing towards an opposite direction of the scroll start point. However, it should be noted that the centre of the siroco fan may be variably moved horizontally and vertically from the spiral center of the scroll casing to make the spiral of the scroll casing a non-linear scroll curve when viewed from the centre of the siroco fan.
Distance (D) where the centre of the siroco fan is detached from the spiral centre of the scroll casing is preferred to satisfy a formula, 0<D≦0.15 R
p3
, where R
p3
is a spiral radius of the scroll start point.


REFERENCES:
patent: 3824028 (1974-07-01), Zenkner et al.
patent: 4143994 (1979-03-01), Yamaguchi
patent: 4512716 (1985-04-01), Marr et al.
patent: 4735551 (1988-04-01), Schilling
patent: 5813834 (1998-09-01), Hopfensperger et al.
patent: 732579 (1980-05-01), None

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