Engineers at Stober Drives Inc., Maysville, Ky., have added two smaller sizes to the company’s line of Servo-Fit PHQ gear units. The PHQ gears feature a four-planet design that handles high torque levels with little backlash, good rigidity, and smooth operation.

The new sizes, PHQ4 and PHQ5, can be equipped with a single or double stage and have ratios ranging from 5.5:1 to 55:1. They handle up to 430 Nm of acceleration torque. Larger versions have gear ratios up to 600:1, and withstand 22,000 Nm of acceleration torque. Backlash for all units is rated at 3 arc-min, but a special version, the PHQA version, can be set up to have backlash as low as 1 arc-min.

The single-piece housing is made of high-tensile tempered steel, and the ring gear is machined into the housing, not welded or pressed in, for better concentricity and more precise alignment. The oversized planet carrier is a single-piece unit that allows it to use higher-load capacity bearings for more torsional stiffness. The FKM seals have the smallest possible diameters for less friction and heat buildup, which allows continuous operation without addition cooling.

The motor-shaft adapter design lets technicians install the units in minutes without special tools. The patented motor coupling handles thermal expansion of the motor shaft, ensuring long motor life by preventing thrust loads on the motor bearings. The triple-split collet, designed for greater concentricity and low inertia, exceeds the gearhead torque capacity. Adapter bushings to fit all motor shafts are provided when necessary and no shaft key is required.

The gear units are said to be well suited for robotics, automation, food packaging, plastic injection molding, and tube bending.