Torque limiter

A torque limiter has an outer sleeve whose interior wall possesses at least one peripheral groove and a plurality of recesses running parallel to the axis. An elastic ring is inserted in each groove. A rolling-element cage has the same number of slots as the number of recesses possessed by the outer sleeve that receives it. A plurality of the rolling elements that are inserted into the rolling element slots. The inner sleeve which slots into the rolling-element cage and whose exterior wall possesses the same number of V-shaped notches—running parallel to the axis—as the number of rolling element slots is provided. A tool or system is provided to restrict the relative torsion between the rolling-element cage and the outer sleeve between a first received position—and a second received position—when the outer sleeve is loosened by rotation and the rolling elements which slot into the notches on the inner sleeve change position vis-à-vis the recesses on the outer sleeve.

BACKGROUND OF THE INVENTION

The invention concerns a torque limiter, in particular a torque limiter suitable for the limitation of the torque of a surgical screwdriver.

Such a torque limiter for a surgical screwdriver is known from DE 600 04 376 T2 and U.S. Pat. No. 6,132,435. The mechanics of the torque limiter is highly sophisticated.

SUMMARY OF THE INVENTION

The invention is based on the task of creating a torque limiter which uses a simple mechanism.

The invention accomplished this task through an outer sleeve whose interior wall possesses at least one peripheral groove and a plurality of recesses running parallel to the axis, (one) elastic ring(s) inserted in the groove(s), one rolling-element cage with the same number of slots as the number of recesses possessed by the outer sleeve that receives it, a plurality of the rolling elements that are inserted into the rolling-element slots, the inner sleeve which slots into the rolling-element cage and whose external wall possesses the same number of V-shaped notches—running parallel to the axis—as the number of rolling-element slots, and the tool to restrict the relative torsion between the rolling-element cage and the outer sleeve between a first received position—when the outer sleeve is turned in the rotational direction whereupon the tool effects a transfer of the torque and the rolling elements align with the recesses and enter the inner sleeve from the notches under pressure from the elastic ring(s) having attained the maximum torque of transfer—and a second received position—when the outer sleeve is loosened by rotation and the rolling elements which slot into the notches on the inner sleeve change position vis-à-vis the recesses on the outer sleeve.

An alternative design consists of an inner sleeve whose exterior wall possesses at least one peripheral groove and a plurality of recesses running parallel to the axis, (one) elastic ring(s) inserted in the groove(s), a rolling-element cage adjacent to the interior sleeve with the same number of slots as the number of recesses, a plurality of the rolling elements inserted in the slots of the rolling-element cage, a rolling-element cage, adjacent to the inner sleeve, whose interior wall possesses the same number of V-shaped notches as the number of rolling-element slots, and the tool to restrict relative torsion between the rolling-element cage and the interior sleeve between a first received position—when the exterior sleeve is turned in the rotational direction whereupon the rolling elements lying in the notches of the external sleeve align with the recesses that they enter from the notches under the force of the elastic ring(s) having attained the maximum transferable torque—and a second received position—when the outer sleeve is loosened by rotation and the rolling elements that slot into the notches change position vis-à-vis the recesses.

The tool operates through the movement of the rolling-element cage vis-à-vis the rolling-element slots so as to create penetrative noses that enter the recesses running parallel to the axis.

The rolling elements may consist of pins or cylinders. The rolling element possessed by the cage may be in the form of needles.

The elastic ring(s) should preferably consist of (an) O-ring(s) manufactured from an elastic material.

The invention will be explained below by reference to drawings which will show

DETAILED DESCRIPTION

The torque limiter consists of an outer sleeve10through which rotational force is exerted on the torque limiter. The inner wall of the outer sleeve10possesses at least one peripheral groove12and a plurality of recesses14that run parallel to the axis and therefore at right angles to the groove. An elastic O-ring16is inserted into each of the grooves12.

The outer sleeve incorporates a rolling-element cage with the same number of recesses14as the number of rolling-element slots18. A rolling element22capable of radial movement is slotted into each of the rolling-element slots18.

The rolling-element cage20possesses a number of noses28that run parallel to the axis and penetrate the recesses14in the outer sleeve10that also run parallel to the axis; these noses28are narrower than the width of the recesses14so that the rolling-element cage20may be rotated at an angle to the outer sleeve until the sides of the noses28nudge against either side of the recesses14.

The rolling-element cage20possesses an inner sleeve24in which the shaft of a screwdriver (not shown) is inserted. The external walls of the inner sleeve24possess V-shaped notches26which may be entered by the rolling elements22.

In the first received position—upon turning the outer sleeve10in the torsional direction—the rolling elements22align with the recesses14. The noses28that lie against one of the walls of the recesses transfer the torque from the outer sleeve10to the rolling-element cage20. Upon the attainment of the maximum transferable torque, the rolling elements22exit the V-shaped notches26in the inner sleeve and penetrate the elastic rings16in the recesses14of the outer sleeve10. This position does not permit any transfer of force between the inner sleeve24and the outer sleeve10that accompanies the rolling-element cage20; further torsion is therefore impossible.

In the second received position—upon turning the outer sleeve in order to loosen it—the rolling elements22received by the notches26in the inner sleeve24change position vis-à-vis the recesses of the outer sleeve10. The rolling elements are returned into the notches26under the pressure of the O-rings16. The noses28, which now lie against the other wall of the recess, effect a transfer of the torque from the outer sleeve to the rolling-element cage and therefore between the outer sleeve and the inner sleeve.

The maximum torque is determined by selecting the O-ring with the desired shore hardness or according to the number of rolling elements that are inserted.

In the alternative design which is shown in cross-section inFIG. 7the grooves12and recesses14are formed on the inner sleeve24and the elastic rings16are inserted in the inner sleeve grooves12and the notches26are formed in the outer sleeve10.FIG. 7is similar toFIG. 3except that the grooves12with elastic rings16are formed on the inner sleeve24and notches26are formed in the outer sleeve10. The outer surface of inner sleeve24has a number of recesses14spaced around the sleeve running parallel to a longitudinal axis of the inner sleeve. The corresponding notches26extend axially along the inner wall of outer sleeve10. Thus this embodiment is the inverse of the design ofFIGS. 1-6.