Rotary expansible chamber devices – Non-metallic working member – cylinder or partition
Reexamination Certificate
2000-03-29
2001-12-04
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Non-metallic working member, cylinder or partition
C418S206900, C418S206100, C418S182000, C264S331110
Reexamination Certificate
active
06325604
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
(Not Applicable)
STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT
(Not Applicable)
BACKGROUND OF THE INVENTION
The present invention generally relates to gear pumps and more particularly to a gear pump housing manufactured from a plastic material which maintains exacting tolerances for proper pumping operation.
Gear pumps are used to transfer fluid from one location to another by pressurizing the fluid. Typically, the gear pump comprises two intermeshing rotatable gears. One of the gears is a drive gear coupled to a driver motor operable to rotate the drive gear to facilitate the transfer and pressurization of fluid. The second gear is an idler gear cooperatively engaged to the drive gear. Both the drive gear and the idler gear contain complementary teeth which mesh with each other in order to rotate the idler gear and transfer fluid.
Both the idler gear and the drive gear are disposed within a gear pump housing manufactured from a metallic material to exacting tolerances. The idler gear and the drive gear are disposed within the gear pump housing such that the outer diameters of each make contact and seal against the gear pump housing. Accordingly, the gear pump housing is partitioned into two chambers defined by the idler gear and the drive gear. Specifically, a bottom chamber of the gear pump housing is defined by the bottom halves of each of the idler gear and the drive gear. Correspondingly, the upper chamber of the gear pump housing is defined by the upper halves of the idler gear and the drive gear. The bottom half or lower chamber of the gear pump housing fluidly communicates with a fluid intake port, whereas the upper half or upper chamber of the gear pump housing fluidly communicates with a fluid outlet port. It will be recognized that by reversing the direction of rotation of the drive gear, the fluid intake port disposed in the lower chamber of the gear pump housing will then become the fluid outlet port and the fluid outlet port disposed on the upper chamber of the gear pump housing will then become the fluid intake port.
During operation of the gear pump, both the idler and drive gears rotate within the gear pump housing. In this respect, fluid may be drawn into the lower chamber of the gear pump housing through the intake port. The rotation of the idler and drive gears within the gear pump housing forces the fluid into the upper chamber of the gear pump housing and hence into the outlet port. The fluid exits the upper chamber of the gear pump housing through the outlet port formed therein. It will be recognized that in order to transfer the fluid from the lower chamber to the upper chamber, both the idler gear and the drive gear must maintain contact with the interior surfaces of the gear pump housing to form a seal therebetween. Additionally, both the idler gear and the drive gear must tightly intermesh in order to form a seal which segregates the lower chamber from the upper chamber.
As previously mentioned, prior art gear pump housings have been fabricated from metallic materials in order to maintain an exacting tolerance between the idler gear and between the drive gear. In this regard, the metallic gear pump housing is manufactured to a size which maintains a seal against the drive gear and idler gear as required for proper operation. However, metallic gear pump housings are expensive to manufacture due to the time and effort required to form the gear pump housing to the correct dimensions. Additionally, metallic gear pump housings are heavy and difficult to work with. Therefore, there is presently a need for a gear pump housing which is inexpensive to fabricate and easy to assemble into a complete gear pump.
The present invention addresses the above-mentioned deficiencies in prior art gear pump housings by providing a gear pump housing which is formed from a plastic material. In this respect, the gear pump housing of the present invention is easy to manufacture and handle. Additionally, the present invention provides a method of forming a plastic gear pump housing which maintains the tolerances needed for proper operation. Specifically, the present invention provides a method wherein the plastic gear pump housing can be manufactured to the tolerances needed for operation with the idler gear and drive gear.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a gear pump comprising a plastic gear pump housing having an interior surface. The gear pump further includes a drive gear and an idler gear each rotatably attached to the gear pump housing and cooperatively engaged to one another. In the preferred embodiment, the interior surface of the plastic gear pump housing is sized to contact the drive gear and the idler gear in a manner to provide a seal therebetween. The gear pump may further include an outer cover engageable to the plastic gear pump housing in a manner wherein the plastic gear pump housing and the cover collectively define an interior chamber of the gear pump. The interior chamber is sized and configured to receive the drive gear and the idler gear of the gear pump.
In the preferred embodiment of the present invention, the drive gear is attached to a drive shaft rotatably connected to the plastic gear pump housing and the idler gear is attached to an idler shaft rotatably connected to the plastic gear pump housing. In this respect, the plastic gear pump housing defines a first axis spaced form the interior surface by a first distance substantially equal to the radius of the drive gear. Similarly, the plastic gear pump housing defines a second axis spaced from the interior surface by a second distance substantially equal to the radius of the idler gear. In the preferred embodiment, the drive shaft extends along the first axis and the idler shaft extends along the second axis.
The drive shaft is coupled to a motor for rotation of the drive shaft and corresponding drive gear. Furthermore, in order to rotate the drive shaft, the motor may include a coupler drive attached to a motor shaft and the drive shaft may include a coupler. In this respect the coupler drive is engageable to the coupler in order to transfer rotation to the drive shaft and drive gear. Furthermore, the coupler or drive coupler may be fabricated from a rubber material in order to prevent wobble and vibration between the drive shaft and the motor.
In accordance with the present invention there is provided a method of forming a plastic gear pump housing for a gear pump. The method comprises forming a plug and then a mold for the plastic gear pump housing. Next, the plug is inserted and secured to the mold in a prescribed position. The plastic gear pump housing is molded by injecting a plastic material into the mold. Finally, the molded plastic gear pump housing is removed from the mold and the plug is removed from the interior of the gear pump housing to thereby form an interior surface of the gear pump housing. The plug is formed with a first plug positioning hole spaced from a first arcuate portion by a first distance substantially equal to the radius of the drive gear. Additionally, the plug is formed with a second plug positioning hole space from a second arcuate portion by a second distance substantially equal to the radius of the idler gear. Typically, the plug is secured within the mold by a drive shaft and idler shaft of the gear pump. Furthermore, it will be recognized that the plug is secured in a position whereat the plug forms an interior surface of the gear pump housing that seals against an idler gear and drive gear of the gear pump.
REFERENCES:
patent: 2833224 (1958-05-01), Meyer et al.
patent: 2966860 (1961-01-01), Maynard
patent: 3128710 (1964-04-01), Blomgren et al.
patent: 3139834 (1964-07-01), Blomgren et al.
patent: 3390638 (1968-07-01), Adams
patent: 3859014 (1975-01-01), Dworak et al.
patent: 4273503 (1981-06-01), Damron
patent: 4583924 (1986-04-01), Zenglein et al.
patent: 4747762 (1988-05-01), Fairbairn
patent: 4925370 (1990-05-01), Tallarita
patent: 6004119 (1999-12-01)
Denion Thomas
Stetina Brunda Garred & Brucker
Trieu Theresa
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