Harmonic drive with crowned drive ring

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#The present invention relates to a harmonic drive according to the preamble of the main claim.

#Reference is made to the further claims and to the following description of a preferred exemplary embodiment of the achievement of the object according to the present invention in regard to further advantages and particular embodiments and refinements and their advantages. In the drawing, which is restricted to the elements essential to the construction and is approximately to scale,

#FIG. 1 shows the construction of the harmonic drive with the housing still unmounted in an exploded view,

#FIG. 2 shows the completely assembled harmonic drive in a view toward the baseplate of its housing, and

#Harmonic drive 10, sketched in FIG. 1 of the drawing in an exploded view, manufactured completely from injection molded plastic parts, and implemented according to the present invention, has a housing 11 with a baseplate 12 in the form of a circular disk. A central through hole 13 is used for engaging drive shaft 14 of a drive motor 15 in drive 10. The diameter of hole 13 is, however, greater than that of shaft 14, so that no radial bearing function occurs in this case.

#Baseplate 12 is equipped in its edge region 16 with profiles such as notches and/or holes for positive engagement with complementary profiles in face region 17 of a support ring 18, to be positioned fixed to the housing, having dimensionally stable internal teeth 19. Therefore, support ring 18 may be, independently from a housing cup 20 to be overlapped later with radial play, fixed on its face using form fit or friction—for example through crimping or soldering and/or gluing—concentrically to through hole 13 and rotationally fixed on baseplate 12. Support ring 18 is then axially and radially overlapped by cap-shaped cup 20, having drive ring 27 inserted, which is also mounted on its face on baseplate 12. Wall 21 of cup 20 is equipped around the circumference with several spring hooks 22, parallel to the axis, for engaging with edge region 16 and baseplate 12 (cf. FIG. 2), like those sketched, in the form of flexible springs cut free in the form of clips having angled free front ends for engaging behind profiled edge region 16. Support ring 18 mounted separately on baseplate 12 in this way provides the particular advantage over a support ring integrated in the hollow cylindrical inner wall of cup 20, as already described above, of its inner teeth 19 being able to be produced more precisely circularly and therefore being able to achieve a low loss, and therefore also particularly low noise, drive operation.

#Opposing bottom 23 of cup 20 represents the free face of housing 11, and therefore also drive 10, and contains the single bearing of this drive 10. For this purpose, cup bottom 23 is equipped with a socket-shaped reinforcement as an end plate for implementing a radial mounting 24 for a drive driven shaft 25 projecting coaxially to motor drive shaft 14. This bottom is connected so it is rotationally fixed to a driven ring 27, which is also cup-shaped or cap-shapedand is provided with dimensionally stable internal teeth 26. Its average diameter is approximately equal to that of support ring 18, which is fixed to the housing and placed axially in front of it in relation to baseplate 12, so that driven ring 27 is axially guided between it and the internal surface of bottom 23 in cup 20. The radial mounting of driven ring 27 is performed in housing bearing 24 using its driven shaft 25, which is anchored in the cup bottom or implemented in one piece with it, and, if necessary, additionally in relation to the hollow cylindrical internal lateral surface of cup or housing wall 21.