Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Patent
1992-08-17
1994-11-29
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
416186R, 416183, E04D 2922
Patent
active
053684435
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a blade wheel for a centrifugal pump. The blade wheel has at least one row of generally radial blades successively in the circumferential direction of the blade wheel, the radially outermost blade ends being at an oblique angle .alpha. with respect to the direction of movement of the periphery of the blade wheel.
Centrifugal pumps are used widely for the transfer of liquid materials and mixtures. Their pumping effect is created by the rotation of a blade wheel in a fixed casing of the pump. The blade wheel subjects the material to be pumped to a centrifugal effect by rotational movement so that, when the material reaches a discharge opening, it is discharged into it under the influence of the centrifugal force and the motion of the blade ends. Such pumps are disclosed, e.g., in DE patent publication 2,525,316 and FI patent 53,747.
A problem with pumps known from the prior art is the pulse-like pressure variation occurring in their discharge conduits, which is disadvantageous under certain operating conditions. In particular, when the pump is used as a feed pump for fibre suspension in the conduit system associated with the head box of a paper machine or the like, the pressure variations cause wave-like variations in the forming paper or cardboard web, thus deteriorating the quality. In an attempt to decrease the pulse, the radially outermost ends of the blades of the blade wheel of a pump have been made oblique in the circumferential direction of the blade wheel, but this has not eliminated the pulse disturbances.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a blade wheel by means of which the output pressure pulse disturbances can be decreased, whereby it will be more suitable for use in the feed pumps for head boxes of paper machines, for instance.
The blade wheel of the invention is characterized in that a circumferential distance between the blades, the axial length of the blades and the angle of the blades in the circumferential direction are such that the leading edge of the trailing blade is in axial alignment with the trailing edge of the leading blade in the circumferential or movement direction, or ahead of said trailing edge in said circumferential direction of movement.
An essential feature of the invention is that the blades of the blade wheel are disposed at such intervals and at such an angle that, when the blade wheel rotates, at least one blade end is always passing by a nose of a discharge conduit of a spiral pump casing for the blade wheel. As a result, the pressure pulse created by the blade end at the nose remains substantially constant all the time, and no appreciable pressure variation occurs in the discharge conduit.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described In greater detail with reference to the attached drawings, in which:
FIG. 1 is a schematic axial sectional view on section I--I of FIG. 2 of a centrifugal pump provided with a blade wheel according to the invention;
FIG. 2 is a partial sectional schematic top plan view of the blade wheel and a nose of FIG. 1 showing the edge of the blade wheel and the radially outermost ends of the blades thereof;
FIG. 3 is a schematic diagram of pressure variation along a discharge conduit of the pump of FIG. 1;
FIG. 4 is a schematic axial sectional view on section IV--IV of FIG. 5 of another centrifugal pump provided with another, two-sided blade wheel according to the invention; and
FIG. 5 is a partial schematic top plan view of the blade wheel of FIG. 4.
DESCRIPTION OF EMBODIMENTS
FIG. 1 shows a centrifugal pump comprising a spiral pump casing 1 within which a blade wheel 3 rotates around the axis of a shaft 2 in the clockwise direction indicated by the arrow. The blade wheel has generally radial blades 4a and 4b successively around its circumference and generally axially between axially opposite-edge discs 3a (only one shown in FIG. 1). The pump casing 1 has a discharge conduit 5 having a nose 6 at the edge of the discharge c
REFERENCES:
patent: 1613816 (1927-01-01), Biggs
patent: 2405283 (1946-08-01), Birmann
patent: 3953150 (1976-04-01), Onal
patent: 4502837 (1985-03-01), Blair et al.
G. Ekman, "The Pulp Industry-Some Difficult Pumping Tasks", Pumps, 1976, pp. 451-455.
Relander Matti
Turkia Erkki
Larson James A.
Look Edward K.
Tampella Forest Oy
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