Vogel phase shifting gearboxes have a second input shaft which suits slow movement of the output shaft with low input power. This is used as an emergency drive in cases where the main drive fails. The in-built high ratio from the worm gear means that the required input torque is low and alternatives to electric motors can be used such as air motors or even hand winding.
Phase shifting gearboxes, also known as speed superimposition gearboxes, are basically a planetary gearbox with one difference in that the outer toothed ring can be rotated through a worm drive. Often this is used to adjust the phase between input and output, or for speed superimposition by applying continuous rotation of the worm gear. When the gearbox input is stopped, perhaps due to a power failure, input of the worm gear gives slow rotation of the output shaft.
Vogel phase shifting gearboxes are available for output torques in the range 15 to 1500Nm. Ratios from input to output for the main drives are 1, 2 or 3, whilst the ratios for the worm gear input range from 40 to 138. These gearboxes are available in the UK through Techdrives; please go to www.techdrives.co.uk for more information.