Seal for ball screw and ball screw utilizing same

• US 20020144560A1
• Filed: 04/01/2002
• Published: 10/10/2002
• Est. Priority Date: 04/05/2001
• Status: Active Grant

• Current Assignee: THK Company Limited
• Original Assignee: THK Company Limited
• Inventors: Nishide, Tetsuhiro, Yatsushiro, Daisuke
• Granted Patent: US 6,931,955 B2
• Time in Patent Office: Days
• US Class Current: 74/89.4
• 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 74/18576 including screw and nut
• CPC Class Codes: Y10T 74/18712 Contamination related
• CPC Class Codes: Y10T 74/18744 Lubrication
• CPC Class Codes: Y10T 74/19702 Screw and nut
• CPC Class Codes: Y10T 74/19744 Rolling element engaging thread

Abstract

A seal for a ball screw is provided with a foreign material removing member having a hole of a shape corresponding to a sectional shape of a ball screw shaft taken perpendicularly to an axis thereof to prevent a foreign material from invading from an outside of a ball screw nut and a seal member having a hole of a shape corresponding to a sectional shape of the ball screw shaft to retain a lubricant existing inside the ball screw nut. The foreign material removing member and the seal member are mounted to the ball screw shaft, at each of both the axial ends of the nut, while being overlapped to each other in a state that inner peripheral portions of the foreign material removing member and the seal member contact an outer peripheral surface of the ball screw shaft and the ball rolling groove thereof. The foreign material removing member is disposed outside the seal member in the axial direction of the ball screw nut.

Claims

1. A seal for a ball screw including a ball screw shaft, a ball screw nut and a number of balls accommodated between the ball screw shaft and the ball screw nut, in which the ball screw shaft has an outer peripheral surface on which a ball rolling groove is formed and the ball screw nut has an inner peripheral surface on which a ball rolling groove corresponding to the ball rolling groove of the screw shaft is formed, said seal for the ball screw being disposed at each of both end portions of the ball screw nut and comprising:

a foreign material removing member having a hole of a shape corresponding to a sectional shape of the ball screw shaft taken perpendicularly to an axis thereof to prevent a foreign material from invading from an outside of the ball screw nut to an inside thereof; and

a seal member having a hole of a shape corresponding to a sectional shape of the ball screw shaft taken perpendicularly to an axis thereof to retain a lubricant existing inside the ball screw nut,

said foreign material removing member and said seal member being mounted to the ball screw shaft while being overlapped to each other in a state that inner peripheral portions of the foreign material removing member and the seal member contact an outer peripheral surface of the ball screw shaft and the ball rolling groove thereof, said foreign material removing member being disposed outside the seal member in the axial direction of the ball screw nut.

2. A seal for a ball screw according to claim 1, wherein said seal member is formed from soft material and said foreign material removing member is formed from a material harder than the material of the seal member.

3. A seal for a ball screw according to claim 1, wherein said seal member is formed from a material absorbing lubricant.

4. A seal for a ball screw according to claim 3, wherein said seal member is formed of a nonwoven fabric.

5. A seal for a ball screw according to claim 1, wherein said foreign material removing member and said seal member are formed in shape of thin plate and another foreign material removing member of the same character as that of the first mentioned one is disposed inside the seal member in the axial direction of the ball screw nut so as to sandwich the seal member between the foreign material removing members.

6. A seal for a ball screw according to claim 1, wherein said foreign material removing member and said seal member are provided with positioning portions so as to be overlapped to each other in a state shifted in circumferential directions thereof at a predetermined angle.

7. A seal for a ball screw according to claim 1, wherein said foreign material removing members and said seal member are formed by punching out thin plates.

8. A seal for a ball screw according to claim 1, wherein said foreign material removing member is provided, at an inner peripheral surface thereof, with a protruded portion in form of spiral to be fitted to the ball rolling surface of the screw shaft and a foreign material removing opening formed so as to extend from an end face of the foreign material removing member directed outward in the axial direction of the nut to a middle portion thereof for scraping and discharging the foreign material outside the nut.

9. A ball screw comprising:

a ball screw shaft having an outer peripheral surface on which a ball rolling groove is formed;

a ball screw nut having an inner peripheral surface on which a ball rolling groove corresponding to the ball rolling groove of the screw shaft is formed;

a number of balls accommodated between the ball screw shaft and the ball screw nut and rolling therebetween; and

seals mounted to both end portions of the ball screw nut in an axial direction thereof,

each of said seals comprising;

a foreign material removing member having a hole of a shape corresponding to a sectional shape of the ball screw shaft taken perpendicularly to an axis thereof to prevent a foreign material from invading from an outside of the ball screw nut to an inside thereof; and

a seal member having a hole of a shape corresponding to a sectional shape of the ball screw shaft taken perpendicularly to an axis thereof to retain a lubricant existing inside the ball screw nut,

said foreign material removing member and said seal member being mounted to the ball screw shaft while being overlapped to each other in a state that inner peripheral portions of the foreign material removing member and the seal member contact an outer peripheral surface of the ball screw shaft and the ball rolling groove thereof, said foreign material removing member being disposed outside the seal member in the axial direction of the ball screw nut.