Machine element or mechanism – Gearing – Teeth
Patent
1999-06-07
2000-09-12
Marmor, Charles A
Machine element or mechanism
Gearing
Teeth
744248, F16H 5517, F16H 118
Patent
active
061161098
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an apparatus for converting a rotational movement into a rectilinear movement, including a threaded spindle, a nut which surrounds the threaded spindle concentrically at a spacing, and a plurality of rolling bodies arranged in this spacing and rolling on the track-forming outer thread of the threaded spindle as well as on the corresponding track-forming thread of the nut, with the rolling bodies being guided by a cage which includes slot-shaped pockets, disposed sequentially at spacings in circumferential direction, for receiving the rolling bodies, wherein during a rotation of the threaded spindle relative to the nut, each rolling body is axially displaceable within the cage by the amount of thread pitch and can be returned to its initial position at the end of this revolution within an axial groove of the nut by a respective cam arranged in vicinity of an end face of the cage.
BACKGROUND OF THE INVENTION
A field of application for a threaded drive of this type for converting a rotational movement into a translational movement is the automobile industry where large-scale production is required while demands on the precision are not of foremost concern. A cost-efficient solution with high degree of efficiency and good load-carrying capability is, however, demanded. German publication DE-OS 21 50 739 discloses such a screw mechanism which has rolling bodies in the form rollers, and includes a massive nut body and two annular cam members which are also massive and have regions with ring-shaped cam surfaces for engagement in ring-shaped recesses on the end face of a cage for the rollers. This design is highly complicated to manufacture, so that a very expensive construction is effected.
German publication DE-OS 22 31 541 discloses a screw mechanism in which a plurality of balls roll between a helical track on a spindle and a helical track of a spindle nut. The spindle nut is made of sheet metal and received in an additional sleeve. For returning the rolling bodies, a circumferential area of the nut has openings to enable the balls to reach the neighboring track winding of the threaded spindle. The additional sleeve is, i.a., required to close the openings to the outside.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a threaded drive which is simple in structure and more cost-efficient to make.
This object is attained in accordance with the invention by arranging as rolling bodies groups of balls in several cage elements, and guiding each cage element for displacement in an axis-parallel manner within one of the slot-shaped pockets of the cage relative to the threaded spindle. This design eliminates the need for an additional sleeve witch surrounds the nut so as to simplify the structure of the threaded drive.
The nut may be a thin-walled sheet metal sleeve formed without cutting. In this manner, a significant material reduction is realized so that the apparatus has a smaller weight.
The sheet metal sleeve, which forms the nut, can be press-fitted in a bore of the housing that receives the apparatus. The press-fit affords the thin-walled, formed without cutting, its precise shape and precise dimensions. Moreover, it can be drawn from a circular blank. During the drawing process, the axial nut for return of the cage elements with the balls can be formed at the same time. The inner thread of the sheet metal sleeve can be made through a roll-forming process.
It is, however, also possible to bend the nut from a sheet metal strip, with the inner thread being previously rolled in. Subsequently, the thus-obtained sleeve is welded along the butt seam.
BRIEF DESCRIPTION OF THE DRAWING
Exemplified embodiments of the invention will now be described in more detail with reference to the drawings, in which:
FIG. 1 is a conventional ball-type threaded drive with a threaded spindle and a nut which is arranged in an additional sleeve;
FIG. 2 is a longitudinal section of a ball-type threaded drive according to the invention, with incorporated cage;
REFERENCES:
patent: 2715925 (1955-08-01), Morgan
patent: 2770155 (1956-11-01), Morgan
patent: 3062070 (1962-11-01), Beatty et al.
patent: 3214993 (1965-11-01), Teramachi
patent: 3884090 (1975-05-01), Dock
patent: 4186621 (1980-02-01), Brusasco
patent: 4542661 (1985-09-01), Teramachi
Feiereisen Henry M.
Ina Walzlager Schaeffler OHG
Marmor Charles A
Pang Roger
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