A powerful new electric linear actuator range provides an alternative
to traditional hydraulic or pneumatic rams
The new Rolaram actuator range from Power Jacks comprises two key
elements: an actuation unit and a drive unit, careful selection of which
determines the performance criteria for load, speed and duty. These units
are compact for their performance rating, and offer flexible mounting,
drive and feedback configurations.
The actuation unit is a basic lead screw assembly. To meet the
performance range, two types are used: a high quality ball screw and nut
for medium duty applications and a roller screw and nut assembly for
medium to heavy duty applications. The roller screw design keeps the unit
compact and ensures a high dynamic load carrying capability and a
practical life rating.
Rolaram's roller screw assembly is Power Jacks' own Spiracon design,
comprising a multi-start screw with involute thread form and a number of
planetary rollers with annular grooves, which engage with the screw. The
rolling action offers high efficiency, while the line contact and
hardened and ground construction takes a high dynamic load with almost no
axial backlash or wear.
The lead screw assembly is packaged inside a ram arrangement with
internal and external guides and seals to provide a sturdy enclosure. At
the drive end of this assembly is a thrust housing which carries the load
from the lead screw to a mounting that allows the unit to be secured to
the surrounding structure.
The drive unit, comprising motor and gearbox, provides the rotary motion,
which the lead screw converts to linear motion. Using a helical or bevel
gearbox allows the motor to be mounted either parallel, in-line or at
right angles to the actuation unit, so most applications can be met
without special modifications. The mounting options for the units are
equally varied and flexible and include classic trunnion-to-clevis and
double-clevis arrangements.
Rolaram linear actuators will produce thrusts from 5kN to 400kN, at
speeds of up to 7m/min as standard, with higher speeds available as an
option. As each actuator will require varying levels of motion control
for each application, the units can be fitted with a wide range of
feedback devices, including encoders (incremental and absolute), limit
switches (mechanical or proximity sensors) and clutches.