Linear actuator needs no gears or brakes
An engineering company based in Barnsley, UK, has come up with a precision linear actuator that needs no gearbox or brakes. EURMotion’s "harmonic linear drive" (HLD) uses a 20-tooth drive pulley on a common shaft with a 21, 22 or 24-tooth drive pulley, combined with a "very clever" belt topology that ensures that the belt is always in tension.
This configuration provides a choice of 2.5, 5 or 10 mm/rev speeds and is equivalent to having a 40:1, 20:1 or 10:1 reduction. The 2.5mm/rev version cannot be back-driven, while the 5mm/rev and 10mm/rev versions will support 13kg and 7kg loads respectively without power.
The timing belt is pre-tensioned and the belt teeth mesh accurately with the drive pulleys, avoiding backlash. A bidirectional repeatability of ±0.03mm is said to be possible, while unidirectional repeatability is better than ±0.01mm. Accuracy is claimed to be comparable to rolled ballscrews, with ±0.1mm per 300mm being attainable. Stroke lengths up to 3.2m are available.
The HLD (shown above) is available either with internal plastic rollers for lightly-loaded applications, or with an external precision linear rail for higher loads.
The HLD is supplied with an integrated servo motor with inbuilt drive and servo controller. The Animatics SmartMotors used for this purpose can deliver thrusts of more than 400N, depending on motor model and the HLD version.
