Ball-screw nut with over-molded shell

Patent metadata

Field	Value
Publication number	US-11530740-B2
Application number	US-201916562649-A
Country	US
Kind code	B2
Filing date	Sep 6, 2019
Priority date	Sep 6, 2019
Publication date	Dec 20, 2022
Grant date	Dec 20, 2022

Abstract

A ball-screw actuator includes a screw nut having a metal core and an over-molded plastic outer shell. The plastic outer shell includes features which would be expensive to manufacture in a single piece metal screw nut, such as an anti-rotation feature, an axial position control feature, and a lateral position control feature. The anti-rotation feature may take the form of an axial groove or of an axial ridge.

First claim

What is claimed is:

1. An actuator comprising:
a screw nut having a metal core and a plastic over-molded outer shell, the metal core having internal threads, and the outer shell having an anti-rotation feature configured to engage a mating feature of a housing to prevent relative rotation therebetween;
a spindle extending through the screw nut, the spindle having external threads;
a plurality of rolling elements disposed between the external threads and the internal threads; and
a locating feature configured to orient the metal core for a molding process of the screw nut, the locating feature configured as a cavity that extends axially from an end of the metal core.

2. The actuator of claim 1 wherein the locating feature:
extends axially from an end of the screw nut; and
includes a first portion arranged on an outer surface of the metal core, and a second portion arranged on the plastic outer shell.

3. The actuator of claim 2 wherein the first and second portions form a blind bore.

4. An actuator comprising:
a screw nut having a metal core and a plastic over-molded outer shell, the metal core having internal threads, and the outer shell having an anti-rotation feature configured to engage a mating feature of a housing to prevent relative rotation therebetween;
a spindle extending through the screw nut, the spindle having external threads;
a plurality of rolling elements disposed between the external threads and the internal threads; and
a locating feature configured to orient the metal core for a molding process of the screw nut; and
the internal threads define recirculation paths arranged radially inwardly of an outer surface of the metal core.

5. The actuator of claim 1 wherein the anti-rotation feature is a groove extending axially along an outer surface of the plastic outer shell.

6. The actuator of claim 5 , further comprising insertable recirculation units configured to redirect rolling elements from a first thread to a second thread adjacent to the first thread, and the groove is arranged circumferentially between recirculation units.

7. The actuator of claim 1 wherein the locating feature is arranged on an outer surface of the metal core.

8. A screw nut for a ball-screw actuator, the screw nut comprising:
a metal core having:
internal threads; and
a plurality of insertable recirculation units configured to redirect rolling elements from a first internal thread to a second internal thread adjacent to the first internal thread, the plurality of insertable recirculation units and internal threads defining recirculation paths configured for the railing elements;

a plastic over-molded outer shell having an anti-rotation feature configured to engage a mating feature of a housing to prevent relative rotation therebetween; and
the recirculation paths arranged radially inwardly of an outer surface of the metal core.

9. The screw nut of claim 8 wherein the plastic outer shell includes an axial position control feature.

10. The screw nut of claim 8 wherein the plastic outer shell includes a lateral position control feature.

11. The screw nut of claim 8 further comprising a locating feature configured to orient the metal core for a molding process of the screw nut.

12. The screw nut of claim 11 , wherein the locating feature is a cavity that extends axially from an end of the metal core.

13. The screw nut of claim 8 wherein the anti-rotation feature includes a thinner portion circumferentially between the recirculation units and a thicker portion covering the recirculation units.

Assignees

• Schaeffler Technologies Ag

Inventors

• De Paula Renato
• Kreutzer Mario
• Adler Dieter
• Zinnecker Michael

Classifications

• F16H2025/204

  Axial sliding means, i.e. for rotary support and axial guiding of nut or screw shaft · CPC title

• F16H2025/2481

  Special features for facilitating the manufacturing of spindles, nuts, or sleeves of screw devices · CPC title

• F16H25/2223 Primary

  Cross over deflectors between adjacent thread turns, e.g. S-form deflectors connecting neighbouring threads · CPC title

• F16H25/2233

  with cages or means to hold the balls in position · CPC title

• F16H2025/249

  Materials or coatings for screws or nuts · CPC title