Information
-
Patent Grant
-
6450764
-
Patent Number
6,450,764
-
Date Filed
Friday, December 15, 200023 years ago
-
Date Issued
Tuesday, September 17, 200221 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Look; Edward K.
- Woo; Richard
Agents
- Lerner, David, Littenberg, Krumholz & Mentlik, LLP
-
CPC
-
US Classifications
Field of Search
US
- 415 1691
- 415 143
- 415 1692
- 415 1693
- 415 131
- 416 223 B
- 417 53
- 417 202
- 417 69
-
International Classifications
-
Abstract
Apparatus is disclosed for pumping a pulp suspension including a housing and an impeller including a central hub, a wheel disk surrounding the central hub, and pump blades extending radially from the central hub along the wheel disk, which includes at least one opening for discharge of an entrained gas from the pump suspension, a vacuum pump at the rear face of the impeller, and vacuum pump blades mounted for rotation within the vacuum pump housing, which includes an outer wall which is eccentrically disposed with respect to the vacuum pump blade, and a rear wall which includes a suction port for receiving the entrained gas, and with the vacuum pump housing mounted adjacent to the central hub to provide a gap therebetween, so that vacuum pump housing is axially adjustable so that the gap can be altered by axial adjustment of the vacuum pump housing.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal pump for pulp suspensions of lignocellulosic material. More particularly, the present invention relates to a pump where gas, such as air, can be separated from the pulp in the pump.
The presence of gas, which follows along with the pulp, causes problems during pumping by centrifugal pumps. The gas in the pulp forms into bubbles, which accumulate in front of the impeller and thereby deteriorate the capacity of the pump. This problem can be remedied by evacuating the gas from the space in front of the impeller, for example by means of vacuum pumps of the liquid ring type. The pumps are often a separate vacuum pump, the suction pipe of which is connected to the sealing space of the pulp pump. They can also be designed as a separate vacuum impeller in the form of a liquid ring impeller located on the shaft of the pulp pump so that a common drive for both impellers is obtained.
In those cases when a separate vacuum pump is used, the pulp pump becomes relatively complicated and expensive, because more components are required in the system. When a separate liquid ring impeller of a conventional type is placed on the same shaft as the pulp pump, the capacity of the liquid ring impeller is restricted for space reasons.
SUMMARY OF THE INVENTION
In accordance with the present invention, these and other problems in the prior art have been eliminated by the discovery of apparatus for pumping a pulp suspension including entrained gas comprising a housing including an inlet for the pulp suspension and an outlet for the pulp suspension, a rotary shaft, an impeller mounted for rotation on the rotary shaft within the housing, the impeller having a front face and a rear face and including a central hub, a wheel disk surrounding the central hub, a plurality of pump blades extending radially from the central hub along the wheel disk, the wheel disk including at least one opening for the discharge of the entrained gas therethrough, a vacuum pump disposed at the rear face of the impeller, the vacuum pump including a vacuum pump housing, a plurality of vacuum pump blades mounted for rotation within the vacuum pump housing, the vacuum pump housing including an outer wall eccentrically disposed with respect to the plurality of vacuum pump blades and a rear vacuum pump wall including a suction port for receiving the entrained gas, the vacuum pump housing being mounted adjacent to the central hub to provide a gap therebetween, an exhaust port for exhausting the exhaust gas therefrom, the vacuum pump housing being axially adjustably mounted whereby the gap between the central hub and the vacuum pump housing can be altered by axial adjustment of the vacuum pump housing, a gas passage disposed radially outside the outer wall of the vacuum pump housing for connecting the at least one opening in the wheel disk with the suction port, and a gas evacuation chamber connected to the exhaust port for evacuation of the entrained gas therefrom. In accordance with a preferred embodiment of the apparatus of the present invention, the apparatus includes a liquid inlet connected to the gas passage for the supply of liquid thereto.
In accordance with another embodiment of the apparatus of the present invention, the apparatus includes a passageway disposed outside the outer wall of the vacuum pump housing for connection of a separate vacuum pump to the gas passage.
The present invention suggests that these problems can be eliminated by the fact that the vacuum impeller is designed to be integrated into the impeller of the pulp pump. The construction is compact and simple, and the capacity of the vacuum pump can be easily controlled. Moreover, the arrangement is formed so that it can easily be combined with a separate vacuum pump so that both pumps can be used in parallel. Alternatively, the separate vacuum pump can be connected at an operation drop-out of the integrated vacuum pump according to the present invention in order thereby to ensure the accessibility for the centrifugal pump.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is described in greater detail in the following detailed description, with reference to the accompanying Figures illustrating an embodiment of the present invention, in which:
FIG. 1
is a side, elevational, sectional view of a centrifugal pump according to the present invention; and
FIG. 2
is a front, elevational, sectional view, taken along line A—A in FIG.
1
.
DETAILED DESCRIPTION
Referring to the Figures, the centrifugal pump shown in
FIG. 1
comprises a pump housing
10
with an inlet
11
and an outlet
12
for the pulp suspension. Such pumps are used at relatively high pulp concentrations, for example from about 8 to 12%. On a rotary shaft
13
in the pump housing
10
an impeller
14
with pump blades
15
is located, which pump blades
15
extend from a hub
16
outward along a wheel disk
17
. On the rear side of the wheel disk
17
rear blades
18
are located. The wheel disk
17
is formed with openings
19
for the discharge of gas collected in front of the impeller. The openings are preferably designed as slits extending from the hub
16
outward.
Behind the wheel disk
17
the hub
16
is provided with vacuum pump blades
20
, which are surrounded by a vacuum pump housing
21
. The vacuum pump housing
21
comprises a cylindrical outer wall
22
and a rear wall
23
. The cylindrical wall
22
is eccentric in relation to the vacuum pump blades
20
so that a liquid ring pump is formed. In the rear wall
23
a suction port
24
and an exhaust port
25
for gas are, respectively, located. The ports,
24
and
25
, are spaced from each other in the circumferential direction, counted for gas suction into the vacuum pump housing and gas exhaust out of the vacuum pump housing, respectively. This effect is brought about by the rotation of the vacuum pump blades and the variations in volume in the circumferential direction of the vacuum pump housing as a consequence of the eccentric location of the wall
22
. The exhaust port
25
communicates with a chamber
26
behind the rear wall
23
for gas evacuation through a gas outlet
27
. In a sealing housing
28
in the pump housing
10
outside the outer wall
22
a gas passage
29
is located for communication between the openings
19
in the wheel disk
17
and suction port
24
.
The vacuum pump housing
21
is axially adjustable in the sealing housing
28
by an adjustment means
30
for setting a gap
31
between the hub
16
of the wheel disk and the outer wall
22
.
An inlet
32
for liquid is connected to the sealing housing
28
for the supply of liquid in the gas passage
29
. The liquid thus supplied is utilized both as drive liquid for the liquid ring in the vacuum pump as well as flush liquid in the passage
29
and in the sealing housing
28
for external flushing of the shaft sealing
34
.
An additional connection opening
33
in the sealing housing
28
to the gas passage
29
can preferably be provided for rendering it possible to connect a separate vacuum pump (not shown).
During the pumping of a pulp suspension from the inlet
11
to the outlet
12
gas enclosed in the pulp will be collected in front of the impeller
14
. The vacuum pump integrated in the hub
16
will then suck in the gas through the openings
19
in the wheel disk
17
and from there through the gas passage
29
into the vacuum pump through the suction port
24
. By the pumping effect brought about by the vacuum pump blades
20
together with the rotating liquid ring in the vacuum pump housing
21
eccentric with respect to the hub
16
, the gas is pumped through the exhaust port
25
and evacuated through the gas outlet
27
.
By adjusting the gap
31
the capacity of the vacuum pump can be controlled. By increasing the gap width the liquid leakage through the gap will increase, whereby the capacity of the vacuum pump is reduced, and vice versa.
In the case when a separate vacuum pump is connected to the connection
33
, this vacuum pump can serve in parallel with the integrated vacuum pump according to the present invention or be connected at an operational drop-out of the integrated vacuum pump. The operation of the centrifugal pump is thereby ensured.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.
Claims
- 1. Apparatus for pumping a pulp suspension including entrained gas comprisinga housing including an inlet for said pulp suspension and an outlet for said pulp suspension, a rotary shaft, an impeller mounted for rotation on said rotary shaft within said housing, said impeller having a front face and a rear face and including a central hub, a wheel disk surrounding said central hub, a plurality of pump blades extending radially from said central hub along said wheel disk, said wheel disk including at least one opening for the discharge of said entrained gas therethrough, a vacuum pump disposed at said rear face of said impeller, said vacuum pump including a vacuum pump housing, a plurality of vacuum pump blades mounted for rotation within said vacuum pump housing, said vacuum pump housing including an outer wall eccentrically disposed with respect to said plurality of vacuum pump blades and a rear vacuum pump wall including a suction port for receiving said entrained gas, said vacuum pump housing being mounted adjacent to said central hub to provide a gap therebetween, an exhaust port for exhausting said exhaust gas therefrom, said vacuum pump housing being axially adjustably mounted whereby said gap between said central hub and said vacuum pump housing can be altered by axial adjustment of said vacuum pump housing, a gas passage disposed radially outside said outer wall of said vacuum pump housing for connecting said at least one opening in said wheel disk with said suction port, and a gas evacuation chamber connected to said exhaust port for evacuation of said entrained gas therefrom.
- 2. The apparatus of claim 1 including a liquid inlet connected to said gas passage for the supply of liquid thereto.
- 3. The apparatus of claim 1 including a passageway disposed outside said outer wall of said vacuum pump housing for connection of a separate vacuum pump to said gas passage.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9802178 |
Jun 1998 |
SE |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/SE99/01002 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO99/66209 |
12/23/1999 |
WO |
A |
US Referenced Citations (6)
Number |
Name |
Date |
Kind |
3644061 |
McFarlin |
Feb 1972 |
A |
4776758 |
Gullichsen |
Oct 1988 |
A |
4981413 |
Elonen et al. |
Jan 1991 |
A |
5116198 |
Vesala et al. |
May 1992 |
A |
5167678 |
Elonen et al. |
Dec 1992 |
A |
5324166 |
Elonen et al. |
Jun 1994 |
A |
Foreign Referenced Citations (3)
Number |
Date |
Country |
0 474 478 |
Mar 1992 |
EP |
0 481 598 |
Apr 1992 |
EP |
WO 9211458 |
Jul 1992 |
WO |