WP6-Brochure-E4 brochure - ELA European Lift Association.

Figure 2‐3. Configuration of Geared traction lift machineroom
(source: Mitsubishi)
Figure 2‐4. Configuration of Gearless traction lift
machine‐room (source: Mitsubishi)
2.1.1 Geared Lifts
Geared lifts are typically used in mid‐rise applications (7 to 20 floors) where high speed is not a
major concern (typical speeds range from 0,1 m/s to 2,5 m/s). The reduction gear allows the
use of smaller, less expensive motors that can thus work at higher speeds, producing the
desired torque.
The machine typically consists of the motor, brake, gearbox and traction sheave. The most
commonly used reduction gear is still of the worm type, comprising a worm and a worm
wheel. The reduction ratio of the gear is given by dividing the number of teeth on the wheel by
the number of starts on the worm. These worm gears are relatively inefficient and are, in some
few cases, being replaced by helical gears.
2.1.2 Gearless Lifts
In Gearless lifts, the sheave is driven directly by the motor, thus eliminating losses in the gear
train. This type of lift has normally been used in high rise applications with nominal speeds
between 2,5 m/s and 10 m/s. However, recent developments have made it available for use in
low rise buildings and for speeds lower than 2,5 m/s.
The machine in gearless lifts consists of a motor, traction sheave and brake. Since the motor is
directly coupled to the traction sheave, there are no transmission losses and they both rotate
at the same speed. The motor must, therefore, rotate at a very low speed – the rope speed is
equal to the circumference of the sheave multiplied by the rotational speed of the motor. For
example, for a rated speed of 5 m/s and a sheave diameter of 750 mm the required motor
speed is of only 128 rpm.
2.1.3 Machine Roomless Lifts
Saving highly valued construction space has always been a concern for lift designers and it has
been the driver of highly innovative technological solutions. Conventionally, all lifts, either
9