Belt-driven linear actuators from Bell-Everman, Goleta, Calif. have had linear force and payload restrictions that limited their use in heavy-duty applications such as packaging and material handling. Recently, however, company engineers addressed this problem by designing the ServoBelt Heavy (SBH). It has 300 lbf of maximum continuous linear force, or four times what previous ServoBelt models could handle.

Maximum payload has also increased, going from 100 to 300 lb, thanks to beefed-up components‚ including the chassis, bearings, and steel-reinforced polyurethane belts.

The new actuator uses Bell-Everman’s dual-belt arrangement in which the lower static belt is adhesively bonded to the chassis and meshed with the upper dynamic belt. A motor-driven pinion riding between the two belts drives the carriage, acting more like a rack and pinion than a traditional belt drive.

Only a small portion of the upper belt is under load at any given carriage position, making the actuator stiffer and more accurate than traditional belt drives. For example, SBH provides a unidirectional positioning accuracy of ±12 μm at speeds up to 13 fps. Dynamic belt life is 5 million cycles at 1,334 N.

With a chassis based on standard aluminum extrusions, SBH can be engineered for travel distances up to 164 ft. A single SBH axis can also support several independently moving carriages.

Applications for the heavy-duty drive include packaging, laser cutting and welding, industrial fabrication, wet-bench systems, and material handling. Multiaxis configurations include Cartesian motion systems and gantry robots.