Machine element or mechanism – Gearing
Patent
1984-02-13
1986-10-14
Staab, Lawrence J.
Machine element or mechanism
Gearing
74764, 74805, 74789, F16H 3702
Patent
active
046165290
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase application corresponding to PCT/EP 83/00148 of June 9, 1983 and based in turn on the German application No. P 32 22 117.7 filed June 11, 1982.
1. Field of the Invention
My present invention relates to a strain-wave transmission which is sealable between input and output sides, in particular for a positioning drive for valve bodies, comprising a strain-wave generator, a deformable strain wheel with support members, and at least one annular gear.
2. Background of the Invention
German patent 29 44 123 shows a strain-wave transmission in which the driving and driven shafts are assigned to different pressure spaces, whose strain wheel designed as a cup-shaped case is axially clamped at one end and at its opposite end is provided with a rigid bottom. Axial forces caused by the system pressure, acting on this bottom, must be dissipated via the peripheral surface of the strain wheel, which may lead to bugging and buckling thereof. Depending on the magnitude of the applied forces, a dependable meshing of the gear teeth is no longer assured or the shell suffers a permanent deformation and thereby becomes useless. Tests have shown that the cup-shaped case cannot stand a prolonged period of operation. The useful life of a strain wheel so constructed is short. Although the forces acting laterally on the peripheral surface of the strain wheel are absorbed by support members, compressive forces acting upon the bottom of the strain wheel cannot be dissipated through the rigid support members. The differential pressure thus requires relatively thick walls in the region of the strain wheel, which additionally increases the deformation work of the strain-wave generator. Besides, the alternating tension stresses a relatively large sealing collar of the cup-shaped case and thereby impairs the sealing against the housing.
OBJECT OF THE INVENTION
The invention has the object of providing a strain-wave transmission with excellent sealability constructed to resist higher pressures than the known transmission according to the preamble and so to attain a higher life span.
SUMMARY OF THE INVENTION
According to the invention the problem is solved by the features recited in the characteristic clause of claim 1.
According to the invention the strain wave transmission has a housing sealable between input and output sides, a strain-wave generator connected with a driving shaft, a deformable cylindrical strain wheel meshing with an annular gear of a driven shaft, the end faces of the strain wheel surrounding support members whose frontal edges are tightly connected with the strain wheel. In this construction: sealingly on the housing by means of a tube segment surrounding the driving shaft.
Compared to that which is known, the invention has the advantages that considerably higher system pressures than heretofore can act without detriment upon the strain-wave transmission, and that greater useful life than heretofore is attainable. Thereby the transmission becomes more versatile in use and the intervals between repairs are significantly prolonged.
The bilaterally cup-shaped, open design of the strain wheel according to the invention, and of the two support members tightly connected therewith at the frontal edge which can be relatively thin-walled in proximity to the edge by virtue of the extensive relief from the differential pressure, enables a reduction of the bulging stress, with a much more uniform stress distribution in the strain wheel and at the support members, whereby the danger of rupture from alternating stresses is considerably reduced and comparatively higher pressure loads become possible.
It is also advantageous that the connection between the support members and the housing is now no longer provided via a part of the strain wheel itself but via a considerably thinner tube, between the bottom and the cover of the housing, which is there more reliably sealable by means of a small sealing flange practically unaffected by the alternate bendings
REFERENCES:
patent: 3077792 (1963-02-01), Kinderman
patent: 3101009 (1963-08-01), Musser
patent: 3119283 (1964-01-01), Bentov
patent: 3187605 (1965-06-01), Stiff
patent: 3196713 (1965-07-01), Robinson
patent: 3407902 (1968-10-01), Musser
patent: 3427898 (1969-02-01), Mayer
patent: 3523488 (1970-08-01), Robinson
patent: 4003272 (1977-01-01), Volkov et al.
patent: 4072067 (1978-02-01), Benthake
patent: 4096766 (1978-06-01), Pardo et al.
patent: 4425822 (1984-01-01), Marschner et al.
Diehl Dwight G.
Dubno Herbert
Ross Karl F.
Staab Lawrence J.
ZF-Herion Systemtechnik GmbH
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