Belts and chains in vertical arrangements

BEMA Series synchronized XYZ gantries from IntelLIDrives use motorized belt mechanisms on their axes to deliver speeds to 2 m/sec — making the gantries suitable for high-speed positioning of medium payloads. Load capacity in X-Y is 30 kg; on the vertical axis it is 2 kg.

Vertical motion axes present potentially dangeroussituations to personnel and workpieces — so usually necessitatefailsafe brakes, mechanical safety linkages, or some type ofemergency-stop equipment. In addition, vertical arrangementssubject their actuator elements to downward or liftoff loads aswell as side loads and moments in pitch, roll, and yaw directions.

So what options are suitable? Actuation based on motor-driven ballscrews and leadscrews works in many arrangements, though it’s not the leading choice for particularly tall installations. Here, trouble with backdriving, buckling, or keeping lubrication evenly distributed over the full stroke may indicate other motion technologies. Belt drives and chain drives are suited to the varied forces of working with and then against gravity — even while resolving other loads.

DON'T DISCOUNT BELTS FOR VERTICAL DESIGNS

Vertical applications employing belt drives often include actuator assemblies complete with twin linear-bearing blocks and guide rails. Such bearings primarily address moment loading during deceleration and acceleration. Safety mechanisms can help keep the machine axis under control, even in the unlikely event of catastrophic actuator failure.

For example, Macron Dynamics offers a timing-belt accessory system called the cam-lock arresting wedge system (CLAWS). This mechanical design has a shuttle that can slide forward up an incline ... and that incline sets itself into any part of a vertical travel to lock and hold the carriage or payload when required.

CABLES AND CHAINS IN ELEVATORS AND HOISTS

More common for hoists and elevators is steel-cable actuation employing direct-drive motors with integrated output-shaft sheaves. Such solutions can reach thousands of feet — and execute such strokes in less than a minute in some instances.

Where elevators must bear heavy loads, worm gearsets on the motor are common to magnify torque capacity. But no matter the motor or gear arrangement, VFDs have become industry standard for motor driving capable of dynamic braking and regenerative operation. These and ultra-efficient clutches and brakes maximize the safety and efficiency of cable-actuated vertical designs.

Another mechanical option to boost efficiency and safety is vertical lifts based on rigid-chain actuation. That’s because resolution of lifting and side loading in complete actuation systems make for more efficient operation. International standards tend to dictate requirements for these designs.

Consider such chain to automate orchestral platforms and theater scenery in shows with high production value: Such rigidchain actuators might raise and lower seating to accommodate various audiences — or platforms and substages during a live show. Carried loads can reach many tons. Such rigid chain includes links (having a square cross section) that coil in a housing and mate when extended to lock into rigid structural columns. This geometry addresses the loads mentioned earlier with optimally positioned center of gravity.

All such rigid-chain systems include feedback devices that sense obstructions and switches that communicate data back to controls. Safety gates underneath actuated stages provide further protection … and operator control pendants can trigger immediate halts to the vertical lifts. Another safety function of rigid chain is avoidance of contamination by hydraulic fluid.