Precision drive for positioning solar energy apparatus

Claim 1

A pair of precision drive trains drivable in opposite directions of rotation for positioning a solar energy collection apparatus by angular adjustment of such apparatus along a pair of perpendicular positioning axes, each drive train including electric motor means, a high transmission ratio primary stage gearing, the electric motor means drivingly engaging the primary stage gearing, the primary stage gearing comprising a harmonic drive, and a secondary stage gear train, the gear train comprising a monoplanetary gear being free of a sun gear and including a planet carrier, the harmonic drive being in driving engagement with the planet carrier, a planet gear, means rotatably mounting the planet gear to the planet carrier about an axis eccentric to the axis of the carrier, the carrier axis being parallel to the respective positioning axis associated with each drive train, an internal ring gear coaxial with the carrier axis, means fixing the ring gear against rotation, the planet gear including gearing means for engagement with the fixed ring gear, a further internal ring gear coaxial with the carrier axis and axially juxtaposed with the fixed ring gear, the further ring gear having a different number of teeth than the fixed ring gear, the planet gearing means comprising a pair of axially contiguous spur gear means, the contiguous spur gear means comprising parts of the same wide gear teeth, one of the spur gear means being in engagement with the fixed ring gear and the other spur gear means being in engagement with the further ring gear, rotation of the planet carrier causing rotation of the planet gear and rotation of the planet gear drivingly rotating the further ring gear by engagement of the planet gear gearing means with the further ring gear, the further ring gear comprising a driven element of the gear train, the planet gear, the spur gear means and the ring gears comprising precision machined gearings assembled for operation with the absence of lash, the secondary stage gear train being self locking in the presence of externally applied torque at the driven element, each gear train further including a pinion, means nonrotationally joining the pinion and the further ring gear, a spur gear, the pinion being in driving engagement with the spur gear, each spur gear being disposed coaxially to the respective positioning axis of each drive train, a casing, the casing carrying both drive trains, the fixed ring gear being fixed relative to the casing, the drive trains further including means for rotatably mounting the casing about one positioning axis and means drivingly interconnecting one drive train with the one positioning axis for rotation of the casing about the one positioning axis by operation of the one drive train, the other drive train further including means drivingly interconnecting the spur gear associated therewith and a driven part, and means mounting the driven part within the casing for rotation about the other positioning axis, the casing comprising two halves joined along a plane extending through the one positioning axis, the driven part coaxial with the other positioning axis being mounted substantially within the casing dividing plane.