Fluid reaction surfaces (i.e. – impellers) – Rotor having flow confining or deflecting web – shroud or... – Radially extending web or end plate
Reexamination Certificate
2000-01-12
2001-04-24
Ryznic, John E. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Rotor having flow confining or deflecting web, shroud or...
Radially extending web or end plate
C416S235000
Reexamination Certificate
active
06220819
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a centrifugal pump impeller and particularly to an impeller that can prevent turbulence at the inlet of the pump for improving pumping efficiency and enables accurate positioning of the vane for the impeller.
2. Description of the Prior Art
In the design and fabrication of impeller for centrifugal pump, how to improve pumping efficiency of the vane and to make positioning of the vane simple in the assembly are some of the heavily focused issues. The surface smoothness at the inlet of the impeller may directly affect flow streamline in the passage and pumping efficiency. To avoid forming abrupt surface change at the impeller inlet is one of the key design consideration. As an impeller usually has at least six blades and each blade is formed in an irregular spiral shape, to accurately position the blades for assembling the vane is not easy. When the blades are not accurately-positioned, the pumping efficiency will be negatively impacted.
Furthermore conventional rear vane cover plate of the pump usually is made by pressing. The cover plate has relatively large size and may result in lower structural strength. It also tends to form corrugation (with rough surface). This phenomenon happens most often to an impeller (or pump) with smaller specific speed. Conventional technique uses increased vane cover plate thickness to enhance strength and employs high cost machining work to further improve cover plate precision. It increases cost and drags down fabrication efficiency.
Some improvement techniques have been announced to address these issues. U.S. Pat. No. 5,082,425 discloses a technique that forms a plurality of corrugation structure on the vane cover plate mating with the vane base to facilitate the blade positioning in the impeller. The corrugation structure needs elaborated design and high precision machining, and also needs accurate soldering work to put the blades in place. The design and fabrication are expensive. Moreover the vanes at the inlet side still cannot totally align with the front end of the hub and suction port. As a result, a not smooth surface will be formed for the vane around the hub and suction port at the inlet area. Flowing fluid easily produces turbulence at this area and greatly impact pumping efficiency.
German Pat. No. DE 44 46 193 C2 discloses another impeller structure that has a plurality of thin spiral vanes soldering to the front and rear vane cover plate by means of laser soldering operation. It may improve surface smoothness of the vane at the inlet and reduce turbulence. However laser soldering operation costs higher, and the blade positioning problem remains unresolved.
SUMMARY OF THE INVENTION
In view of aforesaid disadvantages, it is therefore an object of this invention to provide a centrifugal pump impeller that has smooth surface at the inlet for reducing turbulence and enhancing pumping efficiency. It has simpler structure and costs lower to produce. The vane may be accurately positioned easily.
The pump impeller according to this invention includes a hub, a rear cover plate engaged with the hub, a front cover plate having an inlet and a plurality of vanes. Each vane has a front blade engaged with the front cover plate, a rear blade engaged with the rear cover plate and a blade bridges the front and rear blades. The vanes are located between the front and rear cover plates to form a plurality of spiral pumping passages. The impeller has the following characteristics:
The front blade adjacent the inlet has an indent section which does not extends out of cover plate at the inlet circumference. During pumping operation, fluid may flow into the impeller through the inlet smoothly without producing resistant flow.
The rear blade adjacent the pump spindle has a curved front edge mating closely with the impeller rim for initial positioning use. It also helps to make the vane passage smooth at the inlet around the hub for preventing turbulence. The rear blade has a vane balance hole formed at a front end close to the curved edge mating with a balance hole formed in the rear cover plate. The rear blade further has a positioning hole formed at a rear end thereof. Through these features, the vane may be accurately and easily positioned between the front and rear cover plates. It costs lower and is easier to fabricate and assemble.
In one aspect of this invention, the curved front edge of the rear blade further has a radial cutting edge located at a side remote from the blade. During vane positioning, the cutting edge is extending radially along the spindle. The front tip of the curved front edge of a rear vane (which has a radial cutting angle) may be close to the radial cutting edge of a front vane for preventing turbulence.
In another aspect, the rear cover plate has an outer fold rim formed by pressing that may enhance structural strength with greater precision and avoid the formation of corrugation at the outer rim of the rear cover plate.
It still another aspect, there is a rear sealing ring engaged between the rear cover plate and the impeller. The rear sealing ring has a ring balance hole mating against the rear cover plate balance hole. The rear sealing ring further has teeth-shaped inner ring formed by pressing for engaging with the hub for enhancing the axial alignment and bonding accuracy of the rear sealing ring with he spindle.
REFERENCES:
patent: 751315 (1904-02-01), Lindmark
patent: 1032287 (1912-07-01), Kreher
patent: 1983201 (1934-12-01), Rijswijk
patent: 3260443 (1966-07-01), Garnett et al.
patent: 3298444 (1967-01-01), Haas
patent: 3368744 (1968-02-01), Jenn
patent: 4236871 (1980-12-01), Hirst et al.
patent: 5707209 (1998-01-01), Iyer et al.
Chen Jing-Fuh
Chien Huan-Jan
Kao Shu-Fen
Ou Pao-Yin
Dougherty & Troxell
Industrial Technology Research Institute
Ryznic John E.
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