Telescopic drive is half as deep

Danaher Motion has developed and patented a novel linear drive for applications where a long stroke is needed in a confined space. The Direct Drive Telescope - or DDT - is based on two spindles with opposite pitches, which are nested within each other and move in and out telescopically.

This construction, combined with a direct electric drive which provides a maximum amount of torque in a minimum amount of space, results in a drive that is only half as deep as a conventional device of a similar stroke length.

Because only the outer spindle rotates, the mass being moved is much smaller than that of a conventional spindle with a similar stroke. This allows faster acceleration.

Part of the patent covers an extended rotor that picks up the linear movement of the drive spindle smoothly, and without play. There are no rotating parts to connect to the application, so users do not need to provide complex bearing assemblies, thus simplifying installation.

Because the mechanical parts of the drive also act as motor parts - for example, the rotating part of the telescopic spindle serves as the motor shaft - the number of bearing assemblies is minimised.

An integrated multi-turn shaft encoder eliminates the need for homing when starting up a machine and allows the drive to be connected directly to its controller.

The telescopic drive has a 140mm stroke length, produces a force of up to 35kN, and can move at speeds of up to 0.6m/s. The service life is claimed to be around 20,000 hours. Danaher is developing other versions in different sizes.