Planetary gear transmission systems or components – Planet periphery surrounds axis of interacting gear – Means to change speed ratio between input and output
Patent
1995-05-05
1997-11-11
Wright, Dirk
Planetary gear transmission systems or components
Planet periphery surrounds axis of interacting gear
Means to change speed ratio between input and output
74117, F16H 2916, F16H 2918, F16H 2920, F16H 4816
Patent
active
056857942
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to transmission mechanisms, and preferably to transmission mechanisms capable of providing infinite variation in the drive ratio between the input and output.
Infinitely variable transmissions which operate on a friction principle are well known. One such transmission comprises a vee-belt and pulley system. The pulleys are each split into two frusto-conical portions which are movable axially towards or away from each other so as to vary the effective pulley diameter at which the belt contacts the pulley. The major problem with this and other friction transmissions is that they are unable to transmit high torques, at least without making a transmission of excessive size as to be impractical.
A requirement accordingly exists for a variable ratio transmission which is able to transmit high torques in a practical manner. Transmission systems capable of coping with large torque loads in relatively small units, are inevitably based on rigid body elements such as gears formed in metals. This poses great problems for infinitely variable transmissions, and no practical system exists at this time.
There is disclosed in my patent application PCT/AU81/00146 an infinitely variable mechanical transmission. Basically, this mechanism comprises means for transforming a circular input motion into non-circular periodic motion of a plurality of elements, or iterated operations of a single element, utilising only a part of the periodic motion of each element and transforming this part back into a rotary output motion. These parts of the periodic motion of the plurality of elements are connected or "assembled" sequentially to provide the output motion. This process is what is termed "motion transformation" and results in so-called "torque conversion".
In the transmission disclosed in the above patent application, rotary motion of an input shaft is converted by an eccentric of variable eccentricity into a periodic motion of a plurality of racks. The periodic motion of each rack is converted into a rotary periodic motion of a pinion, and a selected part of the motion of the pinion is applied to a separate satellite gear of a planetary gear arrangement. The resultant output motion of a sun gear of the planetary gear arrangement is effected by the sequential action of each satellite gear. More specifically each rack operates in sequence to apply part of its motion to is associated satellite gear and thus to the output sun gear, a switching device being incorporated in the mechanism to switch on and off an operative connection between a pinion gear which is continually driven by the rack, and the associated satellite gear. While it may be theoretically possible to achieve either instantaneous switching or precise synchronism between the switching off of the operative connection between one rack and its associated satellite gear and the switching on of the operative connection between the next rack in the sequence and its associated satellite gear, it is not possible in practice to achieve this, and as a result the output will not be completely smooth; this may manifest itself as a slight jerkiness which can be felt in the output while under load. Whereas for some uses this lack of smoothness may be tolerated, for many uses it is necessary to obtain a flat or smooth output.
Thus, attempts to produce rigid body continuous variable transmissions have been based on the production of a plurality of partial intermediate circular or non-circular motions produced by a circular input and at some stage transformed back to a collated circular motion. Pires U.S. Pat. No. 4,983,151 issued Jan. 8, 1991 discloses a mechanism which attempts to provide a smooth output by what Pires terms "averaging intermediate rotations". The device disclosed in Pires requires considerable precision and whilst the output is smoother than the transmission referred to in PCT/AU81/00146, the output still is not sufficiently smooth for many applications.
All of these attempts including my earlier patent application No. PCT/AU81/00146, depe
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patent: 5029486 (1991-07-01), Mercat
patent: 5048358 (1991-09-01), Shook
patent: 5454766 (1995-10-01), Mills
Aimbridge Pty. Ltd.
Wright Dirk
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