Implements or apparatus for applying pushing or pulling force – Screw – Geared
Reexamination Certificate
2001-07-23
2002-12-31
Watson, Robert C. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Screw
Geared
Reexamination Certificate
active
06499722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a screw jack used for raising a structural object or a work piece, and more particularly to a screw jack that utilizes a screw.
2. Description of the Prior Art
The conventional automatic three-stage screw jack, as shown in
FIG. 6
, is structurally designed to equip a ball bearing C on a bed B at a lower end of an external cylinder A to receive and support a screw shaft D on the ball bearing C. Therefore, there is a disadvantage that the jack is able to raise an object only up to a level from which the thickness of the ball bearing has subtracted.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a screw jack that is able raise an object up to a higher level in comparison with the conventional one.
According to the present invention, there is provided a screw jack that comprises a thin metal bearing arranged on a bottom surface of a jack body, where the thin metal bearing receives and supports a main screw shaft on the jack body. The thin metal bearing is constructed so as to have a large outer diameter while a stepped sliding-surface is constructed so as to have a small diameter and provided on the top or bottom surface of the large-diameter metal bearing.
REFERENCES:
patent: 5173797 (1992-12-01), Zedekar et al.
patent: 5664762 (1997-09-01), Rothbauer
patent: 6164707 (2000-12-01), Ungchusrie et al.
Darby & Darby
Kawasaki Industrial Co., Ltd.
Watson Robert C.
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