Abstract: A driving hub (6) connected to a first shaft (3) rotatably carries primary planet wheels (10) meshing with first (11) and second (12) sun wheels in coaxial relation. The first sun wheel (11) is fastened to a helical crown gear (16) meshing with auxiliary planet wheels (18) rotatably linked to the second sun wheel (12). Eccentrically projecting from the auxiliary planet wheels are respective interconnecting elements (22) guided in a trochoidal rolling track (23) formed in a guide member (24) fastened to a second shaft (5). Each auxiliary planet wheel (18) is driven by a piston (28) engaged in a pressurization chamber (29) formed in the second sun wheel (12). A fluid supplying circuit (30-35) sends oil under pressure into the pressurization chambers (29) in order to transmit axial thrusts to the auxiliary planet wheels (18), which thrusts, by effect of the helical toothings, produce balanced forces interacting with a motive power so as to transmit motion from the first (3) to the second (5) shaft.

Abstract: The device comprises a driving hub (4, 18) coaxially connected to one shaft (20) and oscillatably engaging a number of planetary gear elements (8, 25) homogeneously distributed around the axis of said hub. The planetary gear elements (8, 25) are engaged between a driven crown wheel (6, 21) which is coaxially fastened to a second shaft (3, 23) and an intermediate crown wheel (7, 24) oscillatably linked to the driven crown wheel (6, 21). The planetary gear elements (8, 25) driven in rotation by the hub (4, 18), are guided by the driven crown wheel (6, 21) and the intermediate crown wheel (7, 24) according to an elliptic path submitting them to a cyclic reciprocating movement relative to the axis of the driving hub (4, 18). An actuator (12, 35) tends to cause the driven crown wheel (6, 21) and intermediate crown wheel (7, 24) to rotate in opposite ways in view of transmitting resultant forces counteracting their being driven by the hub (4, 18) to the planetary gear elements (8, 25).