Machine element or mechanism – Gearing – Teeth
Reexamination Certificate
1999-08-25
2001-05-29
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Gearing
Teeth
C074S441000, C277S354000
Reexamination Certificate
active
06237434
ABSTRACT:
BACKGROUND OF THE INVENTION
It is known to the art to provide the nut of a ball nut and screw assembly with a wiper member having an inner helical thread that is received in the helical groove of the screw. The wiper is typically preloaded by a spring in a direction axially away from the nut end wall, causing the thread of the wiper to be forced axially in one direction against a portion of the side wall of the screw groove in order to minimize axial play or lash between the nut and screw. As the thread of the wiper traverses the screw groove during operation of the assembly, it has a tendency to completely wipe lubricant from this wall portion of the screw groove.
It is a principal object of the present invention to address the lubrication problem associated with the use of a preloaded wiper.
SUMMARY OF THE INVENTION
A ball nut and screw assembly constructed according to the invention comprises a nut and screw having complemental helical lands and grooves providing a helical path or raceway for a plurality of recirculating load bearing balls. A wiper member is carried on the nut and is formed on its inner surface with a helical thread that has the same lead as and rides along the groove of the screw during operation of the assembly. The wiper is displaced axially away from a nut wall by a spring or other preloading or biasing assembly, forcing the thread of the wiper axially in one direction against an opposing side wall of the screw groove in order to minimize axial play or lash between the nut and screw. According to the invention, the axially outboard (relative to the nut) side surface of the wiper thread is formed with a helically extending lubricant collection and retention groove that is operative to retain a corresponding helical ribbon of the lubricant on the radial or side wall of the screw groove in order to insure the most desirable lubrication of the load bearing balls when they come into contact with this side portion of the screw's helical groove.
The invention also contemplates a method of constructing and operating such a ball nut and screw assembly including the provision of the lubricant-retention groove in the load applying face of the wiper thread such that, when assembled with the screw, the wiper of the present invention serves to retain a predetermined amount of lubrication on the wiper-engaged side wall of the screw groove for the benefit of the load bearing balls.
REFERENCES:
patent: 3643521 (1972-02-01), Nilsson
patent: 4052076 (1977-10-01), Wysong
patent: 4407511 (1983-10-01), Benton et al.
patent: 5029877 (1991-07-01), Fedeli
patent: 5906136 (1999-05-01), Yabe et al.
Brown Mark P.
Sepesi David A.
Herrmann Allan D.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Thompson Saginaw Ball Screw Company, LLC.
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