Rotary kinetic fluid motors or pumps – Bearing – seal – or liner between runner portion and static part – Means to seal radial flow pump runner inlet from outlet
Reexamination Certificate
1999-04-12
2001-03-13
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Bearing, seal, or liner between runner portion and static part
Means to seal radial flow pump runner inlet from outlet
C415S200000, C415S204000, C415S206000, C415S214100, C415S915000
Reexamination Certificate
active
06200090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved pump casing for a sheet metal pump and particularly to a pump casing that includes a sheet metal pump body with a reinforced member which has a guide water unit made by casting or injection molding.
2. Description of the Prior Art
Conventional centrifugal pumps are generally made by casting or pressing of sheet metals. The casting method uses cast iron as material which has low stiffness, poor corrosion resistance, and is heavy weight and bulky. It generally has poor durability. It is therefore mainly used for low price pumps. Sheet metal pump made by pressing may have greater mechanical strength, better corrosion resistance such as those made of stainless steel and is light weight and more durable. However sheet meal pump generally has thin casing which is prone to deform under heavy external forces.
It is generally known that the inlet and outlet of the pump casing connecting with outside piping system have to endure great stress resulting from pumping pressure, impeller induced torque and stress, metal strain and stress caused by temperature change and the like. As a result, the pump casing around the inlet and outlet are most likely to deform under pressure. That may cause impeller vibration at high speed and produce excessive friction and noise. To remedy this problem, a number of improvements have been introduced. European Pat. No. EXPO-00442070A1 (Ghiotto) and U.S. Pat. No. 5,310,310 are two of the examples. As shown in
FIG. 1
, the Ghiotto disclosed a sheet metal pump casing
21
which has a seal ring
23
(or wear ring as also may be called) engaged with the pump casing
21
near the inlet end plate
26
adjacent the inlet
22
located at a front end
25
of the impeller
24
of the centrifugal pump
20
.
The seal ring
23
keeps a small gap between the front end of the impeller
24
and the inside wall of the pump casing
21
so that friction may become lower when the impeller
24
rotates at high speed while still having desirable pumping performance. The gap set forth above directly affects pumping efficiency, noise level and durability. Conventional pump has the seal ring fixing to the inlet end plate adjacent the inlet where the deformation is most likely to take place because of the causes given above. Such deformation will cause position shifting of the seal ring and result in greater friction and noise, dropping of pumping efficiency, and shorter durability. Furthermore, the structural strength of conventional sheet metal pumps is general not very strong and consequently reduces its thermo stress strength. Hence the sheet metal pumps made by conventional technique usually work mainly in environments under 150° C.
Moreover, sheet metal pumps made by conventional technique is done by pressing. It is a complex and multiple stages pressing or stamping process to form the tapering cross-section of the volute for containing the impeller. U.S. Pat. No. 5,310,310 discloses a technique that uses multi-stage pressing operations for such purpose. It needs a plurality of different molds. Its production time is longer and the cost is higher. The pressing or stamping operation also tends to produce metal stress concentration that might weaken the mechanical strength of the pump casing.
Conventional metal pump structure also is mostly focused on the reinforcement of the pump casing at the inlet. The pump casing engaging with the motor has often being overlooked. The issues of mechanical strength noise problem and durability at this portion has rarely being addressed. Some may put a back cover
27
(shown in
FIG. 1
) as a supporting means for the pump casing and the motor. It usually does not have strong enough mechanical strength and may produce heavy vibration at high-speed and great noise and results in poor durability as well.
SUMMARY OF THE INVENTION
In view of aforesaid problems and disadvantages, it is therefore an object of this invention to provide an improved metal sheet pump that has a pump casing of greater mechanical strength, lower noise level, better shaped volute and greater durability.
It is another object of this invention to provide an improved metal sheep pump casing that has a separately made water guide unit engaging with a seal ring so that the seal ring may be positioned more precisely and maintain precise gap with the impeller even under pump casing deformation for obtaining lower noise, better efficiency and greater durability.
It is a further object of this invention to provide an improved metal sheet pump casing that has a reinforced structure for the engagement of the pump casing and the motor.
It is yet another object of this invention to provide an improved sheet metal pump casing that has an independent water guide unit which may be made separately from the pump casing so that the pump casing may be produced easily with less stress concentration. The water guide unit may also be produced more precisely by means of 3D machining for enhancing pumping efficiency.
A preferred embodiment of the sheet metal pump casing according to this invention includes a pump body made by pressing or roll forming a sheet metal. The pump body has a basin shape with an inlet end plate at one side and an annular motor end plate at another side. The inlet end plate has an inlet while the motor end plate has an outlet. There is an independent reinforced member made by casting or CNC (computer numerical control) machining. The reinforced member has an annular shape to be housed within the pump body and includes a water guide unit and a flange unit. The water guide unit has a volute formed therein to house an impeller. The flange unit has a plurality of screw bores formed in a lateral side opposite to the inlet. A seal ring is engaged with the reinforced member at the inlet side and has an inner circumference adjacent the impeller around the inlet. The water guide unit and the flange unit may be produced separately and then be assembled together by means of soldering, riveting, adhering, screwing, latching or other mans known in the art. The flange unit may have a wall of cut away openings (or areas) to reduce weight. The water guide unit may be made of plastics through injection molding process and may engage with the seal ring in the injection molding process.
According to one aspect of this invention, the seal ring and the water guide unit may be integrally formed to get greater strength. A dividing ring may be provided and attached to the inlet end plate, and has an annular flange extending toward the impeller adjacent the seal ring for reducing pressure difference between two sides of the seal ring so that the seal ring may be positioned more precisely and has less deformation under pumping pressure. This helps for enhancing pumping efficiency, lowering noise and greater durability.
REFERENCES:
patent: 5069599 (1991-12-01), Carretta
patent: 5112190 (1992-05-01), Kajiwara et al.
patent: 5358380 (1994-10-01), Arakawa
patent: 5385444 (1995-01-01), Kobayashi et al.
Chien Huan-Jan
Pen Charlie
Shih Ming-Chuan
Tang Kuo-Yu
Dougherty & Troxell
Industrial Technology Research Institute
Look Edward K.
Nguyen Ninh
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