Rotary expansible chamber devices – With mechanical sealing – By axially relatively moving working member sections
Reexamination Certificate
1998-04-20
2001-03-27
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
With mechanical sealing
By axially relatively moving working member sections
C418S206100
Reexamination Certificate
active
06206666
ABSTRACT:
TECHNICAL FIELD
The present invention relates to gear pumps generally and more particularly to a unique gear pump having a floating split gear arrangement to enhance pump efficiency.
BACKGROUND OF THE INVENTION
In the past, gear pumps employing a meshed gear set have been used to draw fluid from an input or suction port within a pump housing and to pressurize and pass the fluid to an opposed output or pressure port within the pump housing. Conventionally, such gear pumps have included two elongate meshed gears extending longitudinally of the pump housing between the suction and pressure ports which are located on opposite sides of the meshed gears. The gears are mounted to rotate in gear pockets in the pump housing, and hypothetically when rotating seal against each other in the areas where the gear teeth mesh so that fluid from the suction port is carried around the perimeter of a gear pocket into the pressure port. This action pressurizes the fluid being delivered to the pressure port, and the resulting pressure gradient between the pressure and suction ports results in fluid leakage through any clearances present between the teeth of the meshing gears. These clearances invariably exist due to gear tooth lead error which is waviness or profile error of the involute along the length of the gear. Lead tooth error provides a fluid flow path which increases in area as the axial length of the gears increases, thereby resulting in degradation of the volumetric efficiency of gear pumps employing only two meshed gears.
The volumetric efficiency of known gear pumps is further degraded by fluid leakage between the suction and pressure ports around the ends of the gears. Thus gear tooth manufacturing lead error and the gear end clearance relative to the gear housing result in significant internal fluid pumping losses for a gear pump.
Gear pumps have often been employed as fuel pumps for internal combustion engines, and to meet demands for ever increasing fuel system efficiency, engine performance and lower emissions, it has become necessary to enhance the volumetric efficiency of gear type fuel pumps. To accomplish this, fluid leakage between the low pressure and high pressure portions of the pump must be minimized.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a novel and improved high efficiency gear pump for pressurizing and pumping fluid between a low pressure and a high pressure port while minimizing internal fluid leakage between these ports.
Another object of the present invention is to provide a novel and improved high efficiency gear pump employing split gears to reduce manufacturing gear tooth lead error and internal fluid leakage resulting therefrom.
A further object of the present invention is to provide a novel and improved high efficiency gear pump which provides improved volumetric efficiency by reducing the ability of gear end clearance to cause internal fluid leakage.
Yet another object of the present invention is to provide a novel and improved high efficiency gear pump employing two split coaxial drive gears and two split coaxial idler gears meshing with the drive gears. The split drive and idler gears are mounted for floating axial movement.
A still further object of the present invention is to provide a novel and improved high efficiency gear pump having a pump chamber with spaced endwalls. Two split coaxial drive gears and two split coaxial idler gears meshing with the drive gears are mounted for rotation within the pump chamber between the endwalls with the axes of rotation for the drive and idler gears being normal to the pump chamber endwalls. The split drive and idler gears are mounted for floating axial movement relative to each other and the pump chamber endwalls, and are separated by a single snap ring between each set of gears to insure sealing with the chamber endwalls.
These and other objects of the present invention are accomplished by providing a pump housing which defines an internal pump chamber having first and second spaced endwalls. Between the endwalls, the pump chamber includes opposed first and second elongate gear receiving sections spaced on opposite sides of a central chamber section. The first and second gear receiving sections each have an arcuate peripheral wall which extends between a low pressure chamber section or port and a high pressure chamber section or port positioned on opposite sides of the central chamber section between the first and second gear receiving sections.
A drive shaft is mounted for rotation on the pump housing to extend between the first and second endwalls of the pump chamber. Keyed to the drive shaft for rotation therewith are first and second pump drive gears having teeth which rotate in contact or close relationship with the arcuate peripheral wall of the first gear receiving section. This invention is not specific to any particular key design (woodruff, square, round, etc.). The feature or characteristic of importance is the fact that the key's fit does not prevent axial float of gears. The first and second pump drive gears are coaxially mounted for floating axial movement relative to each other and the pump chamber endwalls, and a single snap ring is positioned therebetween. An idler shaft is mounted in substantially parallel spaced relationship to the drive shaft on the pump housing to extend between the first and second endwalls of the pump chamber. Mounted for rotation on the idler shaft are third and fourth pump idler gears having teeth which mesh with the teeth of the first and second pump drive gears respectively in the central chamber section. The teeth of the third and fourth idler pump gears rotate in contact or close relationship with the arcuate peripheral wall of the second gear receiving section. The third and fourth pump idler gears are mounted for floating axial movement relative to each other and the pump chamber endwalls, and a single snap ring is positioned therebetween.
REFERENCES:
patent: 2955537 (1960-10-01), Gaubatz
patent: 2965036 (1960-12-01), Wood
patent: 3272140 (1966-09-01), Curry et al.
patent: 4259045 (1981-03-01), Teruyama
patent: 4776779 (1988-10-01), Crump
patent: 5092751 (1992-03-01), Viktora
patent: 355193 (1922-06-01), None
patent: 609108 (1948-09-01), None
patent: 1420244 (1988-08-01), None
patent: 1495510 (1989-07-01), None
Barning Jerry R.
Steinrock James G.
Cummins Engine Company, Inc.
Leedom Jr. Charles M.
Nixon & Peabody LLP
Sixbey Daniel W.
Vrablik John J.
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