Ball screw

• US 20050087029A1
• Filed: 05/06/2004
• Published: 04/28/2005
• Est. Priority Date: 05/16/2003
• Status: Abandoned Application

• Current Assignee: Umbra Cuscinetti S.p.A.
• Original Assignee: Umbra Cuscinetti S.p.A.
• Inventors: Chiarappa, Marco, Pacieri, Francesca, Pizzoni, Luciano, Perni, Federico
• Application Number:
  US10/840,193
• Publication Number:
  US 20050087029A1
• Time in Patent Office: Days
• US Class Current: 74/89.400
• CPC Class Codes: F16H 25/2204 with balls
• CPC Class Codes: F16H 25/2418 Screw seals, wipers, scrapers or the like
• CPC Class Codes: Y10T 74/18712 Contamination related
• CPC Class Codes: Y10T 74/19753 Plural independent recirculating element paths

Abstract

A ball screw has a spiral casing mounted coaxially with a shaft; a set of balls interposed between the shaft and the casing; and two seals fitted between the shaft and the casing to define, together with the shaft and the casing, a chamber for containing lubricant; each seal being defined by an annular member made of a first material having a first coefficient of thermal expansion, and by at least one insert located inside the annular member and made of a second material having a second coefficient of thermal expansion lower than the first coefficient.

Claims

1. ) A ball screw comprising a shaft (2) having a given longitudinal axis (3) and an external thread (5);

a spiral casing (6) mounted coaxially with said shaft (2);

at least one set of balls interposed between the shaft (2) and the casing (6); and

two seals (16) fitted, coaxially with said axis (3), between the shaft (2) and the casing (6) to define, together with the shaft (2) and the casing (6), a chamber (17) for containing lubricant; and

characterized in that each seal (16) comprises an annular member (18) made of a first material having a first coefficient of thermal expansion; and

at least one insert (19) located inside said annular member (18) and made of a second material having a second coefficient of thermal expansion lower than said first coefficient.

2. ) A screw as claimed in claim 1, wherein said insert (19) is an annular insert.

3. ) A screw as claimed in claim 1, wherein said insert (19) has a substantially circular cross section.

4. ) A screw as claimed in claim 1, wherein said first material is a plastic material.

5. ) A screw as claimed in claim 1, wherein said first material is a polymer material.

6. ) A screw as claimed in claim 1, wherein said second material is a metal material.

7. ) A screw as claimed in claim 1, wherein each annular member (18) is defined externally by a surface (18a) substantially coaxial with said axis (3), comprises an annular recess (28) opening outwards at said surface (18a), and has an O-ring (29) housed in said annular recess (28).

8. ) A screw as claimed in claim 1, wherein each annular member (18) is defined axially by two surfaces (20) substantially perpendicular to said axis (3), and comprises a number of teeth (23) projecting axially from one of said surfaces (20) and equally spaced about said axis (3).

9. ) A screw as claimed in claim 8, wherein each tooth (23) is substantially sector-shaped.

10. ) A screw as claimed in claim 1, wherein each annular member (18) has an internal thread (22) of substantially the same hand as the external thread (5).