Positive displacement pump and thrust bearing assembly

Details Positive displacement pump and thrust bearing assembly Positive displacement pump and thrust bearing assembly

1999-10-26

2001-08-07

Walberg, Teresa (Department: 3742)

Pumps

Motor driven

Electric or magnetic motor

Reexamination Certificate

active

06270324

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a positive displacement pump and thrust bearing assembly and in particular to a positive displacement pump having a thrust bearing assembly located in communication with the fluid chamber of the pump for controlling rotor clearances between the cover and bracket faces of the fluid chamber.
The optimum clearances between the rotor and the cover and bracket faces in a positive displacement pump must be closely maintained during operation of the pump as these clearances are critical to providing a consistent flow of fluid from the pump. Centrifugal pumps, as opposed to positive displacement pumps, do not require that clearances between the rotor and the cover and bracket faces of the pump fluid chamber be as closely maintained during operation in order to provide a consistent flow of fluid from a centrifugal pump. Magnetically driven positive displacement pumps are shown and described in U.S. Pat. No. 5,165,868, issued Nov. 24, 1992, U.S. Pat. No. 5,263,829, issued Nov. 23, 1993 and U.S. Pat. No. 5,494,416, issued Feb. 27, 1996, all of which are assigned to Tuthill Corporation.
During operation of a positive displacement gear pump the rotor may be pushed towards the cover of the pump by a thrust force created by hydraulic loading on the rotor. The hydraulic loading on the rotor and the resulting thrust force are inherent in the design and operation of a positive displacement gear pump. The magnitude of the thrust force pushing the rotor towards the cover increases as the diameter of the rotor increases and as the pressure of the pumped fluid increases. As the rotor is pushed towards the cover, the clearances between the rotor and the cover and bracket faces of the pump chamber are changed thereby changing the operating efficiency of the pump. The rotor may also be forced into contact with the cover resulting in damage to the pump. The use of a thrust bearing in a positive displacement pump is made additionally difficult due to the exposure of the thrust bearing to the pumped fluid which may contain particulates or which may have poor lubricating qualities resulting in premature wear to the bearing.
SUMMARY OF THE INVENTION
The present invention is directed to an improved thrust bearing assembly for a positive displacement pump. The pump includes a housing defining an internal fluid chamber having front and rear inner walls and a rotor positioned in the fluid chamber for rotation therein. The rotor includes a front face and a rear face, with each rotor face being spaced apart from a corresponding inner wall of the fluid chamber to define a predetermined clearance therebetween. A shaft is connected at one end of the rotor to provide rotation. The shaft extends through a bore within a bracket.
The thrust bearing assembly includes an adjusting collar, a retainer and a thrust bushing. The thrust bushing is positioned within the bore through which the shaft extends and is prevented from moving axially toward the cover of the fluid chamber by a retainer positioned within the bore. The retainer prevents longitudinal movement of the thrust bushing within the bore. An interference fit prevents rotation of the bushing. The bushing radially supports the shaft. The adjusting collar is selectively attachable to the shaft and includes a central bore through which the shaft extends. The adjusting collar includes a circular wall which extends around the shaft. The adjusting collar is connected to the shaft for rotation therewith such that an annular surface of the circular wall of the adjusting collar is in relative rotatable engagement with an annular surface of the bushing. The interaction of the adjusting collar and the bushing prevent movement of the shaft and the rotor in a longitudinal direction toward the cover of the fluid chamber such that the predetermined clearances between the faces of the rotor and the cover and bracket faces are substantially uniformly maintained as the rotor rotates.


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