Rotary expansible chamber devices – With mechanical sealing – Axially movable end wall or end wall portion
Reexamination Certificate
1999-07-08
2001-04-03
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
With mechanical sealing
Axially movable end wall or end wall portion
C418S206100, C418S206400, C418S001000
Reexamination Certificate
active
06210138
ABSTRACT:
TECHNICAL FIELD
This invention relates to rotary pump apparatus incorporating structure for reducing cavitation during pump operation and reducing pump damage caused by cavitation. The invention also encompasses a method.
BACKGROUND OF THE INVENTION
Rotary pumps are well known structures employed to pump fluids from one location to another. Rotary gear pumps conventionally employ two gears having meshing teeth disposed in a rotary pump housing to deliver fluid entering the housing interior from an inlet opening to an outlet opening. One of the toothed gears is a drive gear rotated by a motor or other suitable means while the other gear conventionally is a driven gear driven by and rotating in response to rotation of the drive gear.
It is not at all unusual for cavitation pitting damage to occur in rotary pumps. Typically such damage will be in the form of pitting occurring within the interior of the pump housing. Pump life can be drastically reduced and considerable time and expense can be involved when repairing or replacing pumps having cavitation pitting damage.
DISCLOSURE OF INVENTION
The present invention is directed to a rotary pump apparatus and to a method for reducing cavitation damage.
The rotary pump apparatus of the present invention includes a pump housing defining a housing interior, a fluid inlet opening in communication with the interior and a fluid outlet opening in communication with the interior and spaced from the fluid inlet opening.
A drive gear having drive gear teeth is rotatably mounted relative to the pump housing and located within the housing interior.
A driven gear having gear teeth is rotatably mounted relative to the pump housing and located within the housing interior. The gear teeth of the drive gear mesh with the gear teeth of the driven gear and define therewith a space located between the meshing drive gear teeth and the driven gear teeth varying in volume during rotation of the drive and driven gears.
A fluid-flow passageway extends between the inlet fluid opening and the space for introducing fluid into the space from the fluid inlet opening during increase in volume of the space during rotation of the drive and driven gears to relieve negative fluid pressure within the space during the increase in volume.
The invention further encompasses a method of reducing cavitation in a rotary pump, the pump including a pump housing forming a housing interior and a pair of rotating toothed gears forming a gear mesh located in the housing with the teeth of the gears engaged in the mesh forming a volumetrically variable space during gear rotation.
The method includes the step of establishing a fluid-flow passageway extending to the gear mesh.
Fluid is introduced into the fluid-flow passageway and the method further includes the step of flowing the introduced fluid through the fluid-flow passageway.
The fluid flowing through the fluid-flow passageway is directed into the space during rotation of the gears to relieve negative fluid pressure in the space caused by the rotation.
In the illustrated preferred embodiment, a fluid inlet opening is formed in the pump housing and the fluid-flow passageway is established between the fluid inlet opening and the gear mesh, the fluid flowing into the fluid-flow passageway from the fluid inlet opening.
Other features, advantages, and objects of the present invention will become apparent with reference to the following description and accompanying drawings.
REFERENCES:
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patent: 4830592 (1989-05-01), Weidhaas
patent: 5131829 (1992-07-01), Hampton
patent: 6042352 (2000-03-01), Halter et al.
Denion Thomas
Lampe Thomas R.
Trieu Theresa
Tuthill Pump Group, a subsidiary of Tuthill Corporation
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