Importance

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Abstract

An earth-working machine includes a mobile chassis, a turntable rotatably mounted on the mobile chassis, a carriage rotatably mounted on the turntable in eccentric relation thereto, an earth-working mechanism mounted on the carriage, a source of a fluid pressure, a pair of first and second fluid motors for rotating the turntable and the carriage, respectively, and a fluid rate synchronizer composed of a pair of third and fourth fluid motors interconnected by a common output shaft for discharging amounts of fluid under pressure at a predetermined ratio, the source being operatively coupled to the third and fourth fluid motors, the first and second fluid motors being operatively coupled to the third and fourth fluid motors, respectively, whereby the turntable and the carriage will be angularly moved about their own axes at a constant angular displacement ratio. First and second position detectors are provided for respectively detecting a first angular position of the turntable with respect to the mobile chassis and a second angular position of the carriage with respect to the turntable. An electric control circuit controls solenoid-operated valves to stop the rotation of the first and second fluid motors when the first and second angular positions are reached.

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First Claim