Preloading bearing unit

Details Preloading bearing unit Preloading bearing unit

1999-09-08

2001-01-09

Footland, Lenard A. (Department: 3682)

Bearings

Rotary bearing

Hydraulic or pneumatic bearing support

C384S517000

Reexamination Certificate

active

06170987

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a preloading bearing unit for use with spindle means or the like, and more particularly to such a preloading bearing unit that can be conveniently controlled to impart one of three different preloading pressures.
In order to eliminate the occurrence of a clearance in between a spindle (revolving shaft) and an antifriction bearing, a preloading means may be installed. However, regular preloading bearing means are not adjustable. Adjustable preloading means are seen in U.S. Pat. Nos. 5,388,917 and 5,803,619. However, these two designs still have drawbacks as follows:
1. The preloading pressure can only be adjusted between two levels, namely, the low preloading pressure level and the high preloading pressure level.
2. The hydraulic fluid pressure has to be controlled when adjusting the preloading pressure.
3. Because these design commonly use a single annular hydraulic cylinder to achieve preloading pressure control, the moving parts of the preloading device tend to be stuck.
SUMMARY OF THE INVENTION
The present invention has been accomplished to provide a preloading bearing unit, which eliminates the aforesaid drawbacks. According to the present invention, the preloading bearing unit is mounted within a casing to support an antifriction bearing and the motor shaft of a motor in the antifriction bearing inside the casing. The preloading bearing unit comprises a bushing mounted within the casing around the antifriction bearing, and a hydraulic cylinder assembly controlled to displace the bushing axially on the antifriction bearing, the hydraulic cylinder assembly including first miniature hydraulic cylinders and second miniature hydraulic cylinders alternatively arranged around the bushing, the first and second miniature hydraulic cylinders each having a spring respectively stopped at an outside annular flange at the bushing to impart a pressure to the bushing, first hydraulic fluid delivery pipes and second hydraulic fluid delivery pipes respectively connected to the first and second miniature hydraulic cylinders, a first annular hydraulic fluid accumulation chamber communicated with the first hydraulic fluid delivery pipes for guiding a hydraulic fluid to the first miniature hydraulic cylinders, and a second annular hydraulic fluid accumulation chamber communicated with the second hydraulic delivery pipes for guiding a hydraulic fluid to the second miniature hydraulic cylinders. A different preloading pressure is given to the bushing by turning on the first miniature hydraulic cylinders, the second miniature hydraulic cylinders, or both the first and second miniature hydraulic cylinders, without the need of regulating the pressure of the hydraulic fluid. Because the preloading pressure adjustment is achieved by controlling the operation of the first miniature hydraulic cylinders and the second miniature hydraulic cylinders without changing the pressure of the hydraulic fluid, the hydraulic fluid supply system is less complicated. Therefore, the manufacturing cost of the whole system is relatively low. Further, because multiple miniature hydraulic cylinders are installed, the movable parts of the whole system can be smoothly displaced, and will not be stuck easily.


REFERENCES:
patent: 5743016 (1998-04-01), Manne et al.
patent: 6015264 (2000-01-01), Violette et al.

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