The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 31, 2002
Filed:
Jul. 30, 2001
Soichiro Ohga, Nara-ken, JP;
Tsubaki Nakashima Co., Ltd., Nara-Ken, JP;
Abstract
A ball screw comprising a screw shaft made of steel and having a thread groove on outer peripheral surface, a ball nut made of steel and having a thread groove opposing the thread groove on inner peripheral surface, a return tube attached on the ball nut and a plurality of balls inserted between the two thread grooves and and in the return tube As the balls, steel balls made of bearing steel and ceramic balls made of silicon nitride are disposed alternately at a given ratio. Diameter Dc of the ceramic ball is set to a value smaller than diameter Ds of the steel ball so that contact stress acted on contact surfaces of the ceramic ball and the two thread grooves and will be equal to contact stress acted on contact surfaces of the steel ball and the two thread grooves and