CA1043163A

CA1043163A - Propeller pump

Info

Publication number: CA1043163A
Application number: CA232,039A
Authority: CA
Inventors: Bengt-Ake Brandt; Bo G. Stjernstrom
Original assignee: ITT Industries Inc
Current assignee: ITT Inc
Priority date: 1974-07-23
Filing date: 1975-07-22
Publication date: 1978-11-28
Also published as: GB1510846A; JPS5949435B2; CS191936B2; DE2530214A1; FR2279954A1; NL7508481A; HU175761B; BR7504203A; JPS5148804A; SE384070B; FR2279954B1; SE7409547L; IT1039300B

Abstract

PROPELLER PUMP

Abstract of the Disclosure:

A propeller pump for waste water is supplied which includes a special diffusor having vanes attached to a cylindrical pump housing so that a free central passage is open through the diffusor part, thus diminishing the risks of stoppage from waste material. In addition, the impeller blades are swept backwards and the impeller hub is prolonged forwards and backwards to eliminate winding up of elongated fibres in the pumped medium.

Description

10~3~63

- 2 - ~. A. Brandt et al 4-6 - ~Rev.) BACKGROU~ID Ol;' T}IF, INVENTION
1. Field of the Invention.

This invention concerns a pump of the so called propeller type, which includes a pipe formed as a pump housing and a rotatable impellcr supported thereln.
2. Description of the Prior Art Pumps of this type are often called Axial Flow Pumps, as they are so formed that the pumped medium passes mainly axially through the impeller. In conventional centrifugal pumps, or Radial Flow Pumps, the pumped medium is on the contrary perpendic-- ular linked when it passes the impeller.
~ Pumps of the last mentioned type are very common in a number of fields of application and for use in pumping waste water they have been dominant up to now. A disadvantage with this type of pump is that it, because of its construction, always has a certain limited through-way area, which prevents bigger obiects from passiny.
Furthermore elongated non-rigid objects, for instance ropes and .
strings, may have'a tendency to wind up on the impeller thus causing ~toppage.
- Another disadvantage of radifll pumps, in comparison with axial flow pumps, is that they are of more complicated construc,tion and re~uire a larger amount of material per unit.
It has therefore long appeared desirable to be able to , use pumps of the axial flow type for pumping waste water. This appears especially so when l~rge volumcs of flow are involved, as the savings of materials are more important with larger pump units.
A reduced material demand means naturally both decreased weight and lower costs.

- 2'-10431~3

- 3 - B. ~. Brandt et al 4-6 (Rev.) Up to now, tests of axial flow pumps used for pumping waste water have not been successful, above all oecause of the fact that the efficiencies of such pumps have been too low. In ordcr to obtain an acceptable efficiency, the pump housing must be provided with a diffusor aftcr the impeller, wbich diffusor transfers the moving energy of the pumped medium into pressure energy. Diffusors, which mainly consist of a number of vanes fix~d to a central hub, have proven to be a cause of stoppages of the O pumps.
SU~IM~RY or T~IE INVF.T~TI~I~
According to the invention, the problem has been solved by providing the pump housing, at its pressure side, with a number of radial diffusor vanes, which extend inward from the mantle surface of the pump housing and are so formed that a free central passage remains and the diffusor vanes have a decreasing radial extcntion in the dircction towards the pump im~eller.
Brief Description Of The Drawings ~ ~ -The invention is described more closely below with reference to the enclosed drawing, showing an embodiment of the invention in partial section.
Description of a Preferred Embodiment .
!0 In the figurcs, 1 stands for a cylinder formed pump housins with a pump i~pellcr 2, 3 stands for the driving shaft, 4 the impeller blades, 5 the prolongcd inlet collar of the impeller and 6 its extended hub. 7 Stands for the gap between the impeller and the pump housing, 8 rcprescnts the diffusor vancs and 9 an empty ccntral space.
~5 Thc pumpcd mcdiu~ flows in the direction of thc arrows.
In order to prcvcnt material with elongatcd fibers from beincJ wound up around the driving shaft 3, the pump impeller is elongated and ` 1~)431~;3

- 4 - B. A. Brandt et al 4-6~Rev.) terminated with an inlet collar 6 having a relatively big diameter.
This construction enables fibrous material to go further without being wound up.
The impeller blades 4 are secured to a relatively large hub and have a maximum radius which is somewhat smaller than the inner radius of the pump housing, so that a gap occurs between the impeller blades and the pump housing wall. This gap, which is of a size of up to 10~ of the inner diametcr of the pump housing, is provided to assure that material with long fibers will not get stuc~
O between the outer parts of the blades and the pump housing wall.
Further, the lcading edges of the blades are swept backwards thus transporting long fibers outwards against the periphery.
The pump impeller has a hub 6 prolonged backw~rds, which is necessary to reduce the pressure drop after the impeller. The prolonged hub may be formed like a cut cone or a hemisphere. It is important that the sur~ace be smooth so that objecLs do no, stick to the surface but skid off of it. In theory it is possible to replace the prolonged hub by a body of about the same shape attached to the pump housing. In practice, however, it is difficult to attach O it to the pump housing without running the risk of thc attaching means originating stoppages.
The diffusor part, 8, is also formed to minlmize the risk of stoppage.By attaching the vanes to the inner periphery of the pump housing, the conventional diffusor hub is eliminated, thus providing a free central through-way 9. Further, the leading edges of the vanes heading thc flow direction are swept backwards to bring long fibers towards the center and the free through-way 9. The risk of such material causing stoppages is then almost eliminated.
8y a combination of steps according to the invention, a device ha~

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1043~63

- 5 - B.A.Brandt et al 4-6(Rev.) thus been obtained which unites the best qualitics of conventional centrifugal and axial flow pumps regarding efficiency and ability to transport media containing big solid bodies as well as material of a long fiber nature. The pump is primarily meant for pumping of i sewage water but applications in other fiélds are possible.
While the principles of the invelltion have been described a~ove in connection with specific apparatus and applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.

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Claims

WE CLAIM:

1. A propeller pump comprising a pump housing having a substantially cylindrical section with an interior mantle sur-face, means supporting a rotatable pump impeller in said housing, the housing providing a path for fluid flow along the axis of the pump impeller, the impeller including a number of radial blades to enable high pressure to be supplied near one end of the impeller, the radial blades having outer edges which are spaced-apart from said interior mantle surface to provide a blade-free space within the interior mantle surface forming an annular axial passageway for the passage of fibers therethrough, the pump housing supporting a number of radial diffusor vanes near the high pressure end of the impeller, said diffusor vanes extending inwardly from the mantle surface of the pump housing to leave a free central passage through the housing, and said impeller blades and said diffusor vanes having leading edges swept backwards to promote the movement of fibers toward said annular passageway and said central passage.