Planetary gear transmission systems or components – Planet pinion engages flexible belt or chain
Patent
1993-08-17
1994-11-01
Look, Edward K.
Planetary gear transmission systems or components
Planet pinion engages flexible belt or chain
475331, 475169, F16H 358, F16H 376
Patent
active
053603800
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to epicyclic drive transmissions or gear boxes of the kind having a fixed central axis and comprising a rotatable driving element with said fixed axis as its axis of rotation, a rotatable driven element also with said fixed axis as its axis of rotation, a central sun wheel fixed relative to one of said elements so as to rotate in concert with said one element also with said fixed axis as its axis of rotation, a stationary outer ring member co-axial with said elements, a planet carrier fixed relative to the other of said elements so as to rotate in concert with said other element with said fixed axis as its axis of rotation and defining an orbiting axis of rotation parallel to and radially spaced from said fixed axis, and at least one planet wheel mounted on said carrier for rotation about, and orbital movement with, said orbiting axis; said planet wheel being simultaneously engaged with said sun wheel and said ring member.
BACKGROUND ART
Such transmissions are usually reversible and the driving element may become the driven element and vice versa depending on the external circumstances, but for descriptive convenience it is assumed hereinafter that the element fixed to the planet carrier is the driving element.
Briefly stated, such transmissions operate as follows. The driving element is rotated by an external power source and it causes the planet carrier to rotate about the transmission's stationary axis. The planet carrier therefore causes the planet wheel to orbit with the orbiting axis, that is to say causes the planet wheel to roll around the stationary ring member, which causes the planet wheel to rotate about its own (the orbiting) axis. The planet wheel is engaged with the sun wheel and therefore the rotation of the planet wheel causes the sun wheel to rotate to a greater or lesser extent, depending on the extent to which the orbital movement of the planet wheel about the sun wheel augments or diminishes the effect of its rotation on that wheel. The rotation of the sun wheel induced by the combined effect on it of the orbital movement and rotation of the planet wheel is transmitted to the driven element.
The velocity ratio of such a transmission is determined by the relative values of the diameters of the ring member, planet wheel and sun wheel. Thus if the diameters of the planet wheel and sun wheel are left unchanged, the velocity ratio could be varied by altering the diameter of the ring member. Indeed proposals to provide variable ratio epicyclic or similar transmissions wherein the ring member is of variable diameter have been put forward hitherto. One such is the transmission described and illustrated in the International patent application PCT/AU/89/00241 published under publication No. WO 89/12185.
DISCLOSURE OF INVENTION
There are two design problems inherent in such variable ratio transmissions, namely member and sun wheel as the ring member's diameter is varied.
In common with many other variable ratio drive transmissions, for example non-epicyclic variable ratio drives, the transmission of the above mentioned International application overcomes design problem (i) above by utilising frictional contact between the ring member and that proposal's equivalent of a planet wheel, for the transmission of torque therebetween. It is relatively easy to vary the effective geometry of the ring member while maintaining a simple rolling contact with another component, but the problem is much more intractable if a more positive, meshing gear type engagement is required, so as to retain the greater torque transfer capability of such by comparison with that available from mere frictional contact. That prior art proposal meets (ii) above by a complex arrangement of nested eccentrics.
Therefore an object of the present invention is to provide a simple, efficient, variable ratio, epicyclic drive transmission providing a positive drive between the driving and driven elements.
In meeting that object the invention addresses problem (i) above by providing a ring mem
REFERENCES:
patent: 3675509 (1972-07-01), Widdershoven
patent: 3949619 (1976-04-01), Kuehl
patent: 4567789 (1986-02-01), Wilkes
patent: 5033995 (1991-07-01), Salesse
patent: 5074829 (1991-12-01), Menge, Sr.
Lee Michael S.
Look Edward K.
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