Planetary gear transmission systems or components – Planet periphery surrounds axis of interacting gear – Gear has plural circumferential tooth sets
Patent
1999-01-12
2000-10-10
Wright, Dirk
Planetary gear transmission systems or components
Planet periphery surrounds axis of interacting gear
Gear has plural circumferential tooth sets
F16H 132
Patent
active
061296473
DESCRIPTION:
BRIEF SUMMARY
A planacentric gear box has a gear ring with internal teeth meshing with a gear wheel with external teeth, the number of teeth of the gear wheel beeing slightly smaller than the number of teeth of the gear ring, the center-distance between the gear wheel and the gear ring is very small, it is half the difference of number of teeth multiplied by the module. By the means of eccentrics, the gear wheel orbits inside the gear ring, this allows to obtain a big ratio with one gear train, its value is number of teeth of gear ring divided by the difference of number of teeth between gear ring and gear wheel. The orbiting of gear wheel inside the gear ring can be made by a synchronised rotation of two eccentrics whose axles are parallel to the axles of gear wheel and gear ring, those eccentrics rotates in the elements that orbits. The eccentric bearings carry the efforts corresponding to the low speed output torque but they rotate with the speed corresponding to the output speed multiplied by the ratio of the planacentric gear train; consequently those bearings carry big loads with a relatively fast rotation. A way to reduce reactions on those bearings is to increase the center distance between the two eccentrics having them located outside the gear ring, this configuration can be seen on FIG. 1 of Euro patent application 0 465 292 A1 of Mr. Periou but in this case it is the gear ring that orbits around the gear wheel and this does not allow to transmit efforts, their is an incompatibility between the directions of the rotation of the gear wheel and of the efforts on the meshing teeth. When the difference of number of teeth between gear ring and gear wheel is small, 2 or 4, the meshing conditions are such that on one hand it is surfaces and not lines that carry the loads and on the other hand the gliding between the carrying teeth is practically none, the teeth work like splines, consequently the loads that such a planacentric gear train can carry are enormous, their limit is not fixed by the teeth but by the eccentric bearings and by the ovalisation of the gear ring.
The present invention is a planacentric gear box which uses the advantages of this type of gear box:
This minimising the disadvantages:
This planacentric gear box has a low speed hub with a circular rib whose periphery is connected to a gear ring with internal teeth which meshes with a gear wheel with external teeth, this gear wheel orbiting inside the gear ring by the means of two eccentric shafts which are synchronously driven by prime reducers having, in a well known manner, cylindrical gears, bevel gears, worm gears or toothed belts, those prime reducers beeing driven by a common input shaft; planacentric gear box for which the eccentic bearings are located outside the gear ring, this gear ring is rigidly connected to the low speed hub and the gear wheel is fixed on a torque arm which passes beside the gear ring, this torque arm has, diametricaly opposed, two protuberances which receive each the outer ring of the bearings for the eccentrics which are generating the orbitation of the torque arm and consequently of the gear wheel, the median planes of the gear wheel and of the eccentric bearings are close one to the other, the eccentric shafts are journaled in the side walls of the gear box housing. This configuration is good for very low output speeds which means that the centrifugal forces due to orbitation can be neglected. For rotation speeds of the eccentric shafts bigger than 150 R.p.m. the orbiting masses can generate centrifugal forces which may not be neglected, those forces have to be compensated and for the planacentric gear box according to the invention, the low speed hub has a circular rib located in its median plane whose periphery is rigidly connected to the median part of a gear ring with internal teeth which is divided in two equal parts by the circular rib of the hub. Each part of the gear ring meshes with a gear wheel with external teeth which are each respectively connected to a torque arm passing on each side of the gear ring. T
REFERENCES:
patent: 5232412 (1993-08-01), Zheng et al.
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