| 摘要 |
A drive assembly includes a casing containing a planetary gear assembly. A speed control arrangement is provided in association with the planetary gear assembly to vary the speed of rotation of an output member relative to the speed of rotation of an input member. The speed control arrangement includes a first disc pack which is engaged under the influence of a spring to prevent relative rotation between a ring gear and a planet carrier. A second disc pack is also engageable under the influence of a spring to prevent rotation of the ring gear relative to the casing. Hydraulic motors are selectively operable to release the disc packs against the influence of the associated springs. In the event of a failure in the source of hydraulic fluid, both disc packs are engaged with a resulting braking of rotation of the driven wheel. A secondary or towing clutch is selectively disengageable to release the output member and wheel for rotation, even though both of the disc packs are engaged. The springs cooperate with the disc packs in such a manner that wear is minimized. Compact construction of the drive assembly is promoted by eliminating the use of bearings to hold the ring gear against sidewise movement. The compact construction of the drive assembly is also promoted by forming the ring gear with a pair of annular side sections which have the same inside diameter and which extend axially outwardly from opposite sides of the ring gear into engagement with disc packs.
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