Ball nut with tangential no load-guided return path

• US 5,142,929 A
• Filed: 03/29/1991
• Issued: 09/01/1992
• Est. Priority Date: 03/29/1991
• Status: Expired due to Fees

• Current Assignee: Robec Incorporated Rancho Cordova California
• Original Assignee: Robec, Inc. (AmeriQuest Technologies, Inc.)
• Inventors: Simpson, Glenn R. III
• Primary Examiner(s): Herrmann, Allan D.
• Assistant Examiner(s): LAUB, DAVID
• Application Number:
  US07/677,797
• Time in Patent Office: 522 Days
• Field of Search: 74/89.15, 74/424.8 R, 74/459
• US Class Current: 74/424.87
• CPC Class Codes: F16H 2025/2242 Thread profile of the screw or nut showing a pointed "gothic" arch in cross-section
• CPC Class Codes: F16H 25/2214 with elements for guiding the circulating balls
• CPC Class Codes: Y10T 74/19772 Rolling element deflector

Abstract

A ball nut (60) has internal return paths (62) for a pair of parallel helical tracks (64). The return paths (62) are formed by grooves (66) machined into the body of the ball nut (60) from one end of the helical tracks (64) to the other. Return guide covers (68) and return guide inserts (69) are inserted into the ball groove tracks (64) on each end of the tracks. These covers (68) and inserts (69) divert the ball bearings through the grooves (66) and into the opposite end of the circuit formed by the helical tracks (64). The ball bearings (82) are deflected by the return guide insert (69) smoothly in a tangential path from the helical track (64). Thus, no abrupt change in direction for the ball bearings (82) while they are under load is encountered.

Claims

1. A ball nut, which comprises a body having an axial bore extending through said body, at least one substantially helical path track on said axial bore for receiving a plurality of ball bearings for engaging threads of a lead screw, at least one return path for said plurality of ball bearings connecting ends of said at least one substantially helical path track and at least one pick-off for said plurality of ball bearings connecting said at least one substantially helical path track and said at least one return path to deflect said plurality of ball bearings from said at least one substantially helical path track while said plurality of ball bearings are under no load, said at least one pick-off engaging said at least one substantially helical path track tangent to said at least one substantially helical path track, said at least one pick-off comprising a return guide insert engaging said at least one substantially helical path track and said at least one return path including a return guide cover engaging said return guide insert, said return guide insert and said return path cover each having mating curved passages to define a smooth curve path from said at least one substantially helical path track to said at least one return path, said at least one substantially helical path track being configured adjacent to said at least one pick-off so that one of said plurality of ball bearings is free of load when adjacent to said at least one pick-off.

2. The ball nut of claim 1 in which said at least one return path comprises a groove in an outer surface of said body, said ball nut additionally having a sleeve over the outer surface of said body.

3. The ball nut of claim 2 in which said body has a plurality of parallel substantially helical path tracks for receiving the plurality of ball bearings and a return path groove in the outer surface of said body for each of said plurality of parallel substantially helical path

4. The ball nut of claim 1 in which said at least one return path has one of said at least one return guide insert and one of said at least one return guide cover at each end of said return path, one of said at least one return guide insert and said return guide cover serving as one of said at least one pick-off, and another one of aid at least one return guide insert and said at least one return guide cover serving to supply said plurality of ball bearings from said at least one return path to said at least one substantially helical path track.

5. The ball nut of claim 1 in which said at least one substantially helical path track and said at least one pick-off are configured and positioned relative to one another so that one of said plurality of ball bearings entering said at least one pick-off is free of load when deflected from said at least one substantially helical path track by said at least one pick-off by providing a gap between the one of said plurality of ball bearings and said at least one substantially helical path track adjacent to said at least one pick off.

6. A ball nut assembly, comprising the ball nut of claim 1 in combination with a lead screw in said axial bore, and a plurality of ball bearings between said at least one substantially helical path track and said lead screw.

12. A ball nut assembly, comprising the ball nut of claim 6, a lead screw in said axial bore, and a plurality of ball bearings between said spiral track and said lead screw.

13. The ball nut of claim 1 in which said return guide cover and said return guide insert are configured so that said return guide cover fits over and engages said return guide insert to connect said return guide insert and said return path.

7. In a ball nut having a body with an axial bore having a spiral track for receiving a plurality of ball bearings between the spiral track and threads of a lead screw, a return path connecting first and second ends of the spiral track, and a pick-off connected between the first end of the spiral track and the return path, the improvement comprising said pick-off including a return guide insert engaging said spiral track and said return path including a return guide cover engaging said return guide insert, said return guide insert and said return path cover each having mating curved passages to define a smooth curve path from said spiral track to said return path, said spiral track being configured adjacent to said pick-off so that one of said plurality of ball bearings is free of load when adjacent to said pick-off.

8. The ball nut of claim 7 in which said return path comprises a groove in an outer surface of said body, said ball nut additionally having a sleeve over the outer surface of said body.

9. The ball nut of claim 8 in which said body has a plurality of parallel spiral tracks for receiving the plurality of ball bearings and a return path groove in the outer surface of said body for each of said plurality of parallel spiral tracks.

10. The nut of claim 7 in which said return path has said return guide insert and said return guide cover at a first end of aid return path and a second return guide insert and a second return guide cover at a second end of said return path, one of said return guide insert and said second return guide insert and said return guide cover and said second return guide cover serving as said pick-off, and another one of said return guide insert and said second return guide insert and said return guide cover and said second return guide cover serving to supply said plurality of ball bearings from said return path to said spiral track.

11. The ball nut of claim 7 in which said spiral track and said pick-off are configured and positioned relative to one another so that one of said plurality of ball bearings entering said pick-off is free of load when deflected from said spiral track by said pick-off by providing a gap between the one of said plurality of ball bearings and said spiral track adjacent to said pick off.

14. The ball nut of claim 7 in which said return guide cover and said return guide insert are configured so that said return guide cover fits over and engages said return guide insert to connect said return guide insert and said return path.

15. In a ball nut having a body with an axial bore having a spiral track for receiving a plurality of ball bearings between the spiral track and threads of a lead screw, a return path connecting first and second ends of the spiral track, a first pick-off connected between the first end of the spiral track and the return path, and a second pick-off connected between the second end of the spiral track and the return path, the improvement comprising said return path being formed in an outer surface of said body, said first and second pick offs including first and second return guide inserts respectively engaging the first and second ends of said spiral track and said return path including first and second return guide covers respectively engaging said first and second return guide inserts, said first and second return guide inserts and said first and second return path covers each having mating curved passages to define a smooth curve path from said spiral track to said return path, said first and second return guide covers and said first and second return guide inserts being configures so that said first and second return guide covers fit over and engage said first and second return guide inserts to connect said first and second return guide inserts and said return path, and a continuous, cylindrical sleeve fitting over said body and covering said return path, said first and second inserts and aid first and second return guide covers.