Anti-backlash mechanism for machine drive

Abstract

An anti-backlash mechanism for a machine drive is disclosed, wherein a shaft carries a rotary worm wheel having drive connections to the tangs of two back-to-back clutch units. The first clutch unit is connected to a rotatable shaft, concentric with the worm wheel, and having a first helical gear on its end. A second helical gear on the support shaft is torsionally and axially free to slip. The second gear is connected to the second clutch unit by a torque tube permitting relative axial movement to occur between the two. A first actuator biases the two gears apart, and a second actuator between the second helical gear and the clutch units provides clamping force to engage the mechanism. An output bull gear is in mesh with the pair of helical gears. To engage the mechanism, the second actuator is energized, impressing a snugging force on the discs of the clutch units, and driving the second helical gear in an axial direction toward the first helical gear. Continued movement in an axial direction causes the clearance to be taken up between the teeth of the helical gears and the tooth space of the bull gear and will cause the gears to roll with respect to one another, thus taking the shake out of the spline teeth and drive tang connections between the clutch units and the worm wheel. When the second helical gear 'bottoms', pressure build-up in the second actuator will cause maximum clamping force to be realized by the clutch units thereby preloading all parts for maximum drive stiffness.