Power Jacks Rolaram Linear Actuators - Manual (Page 9)

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LINEAR ACTUATORS
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Rolaram
Operating Life and Duty
The actuator models listed in the Technical Charts are capable of very high operating lives (in excess of 10,000 hours for some high speed
models). The ball screw version may have a lower life expectancy than the equivalent roller screw version. Due to the almost limitless
number of possible configurations, please consult our Technical Sales Department for an estimate of life for individual applications.
Continuous duty applications e.g. reciprocating pumping systems can also be realised.
Efficiency
The inherent high efficiency of the screw and helical spur and spiral bevel gear system combine to give an overall mechanical efficiency of
typically 80%. Power consumption is therefore minimised and a compact actuator is assured.
Synchronisation
Synchronisation of two or more Rolaram actuators can be achieved in one of two ways, depending on the requirements of the application:
•
Using encoders, synchronous motors or servo systems (i.e. each unit motorised)
• By linking the units mechanically with drive shafting, driven by one common motor
Positional Accuracy
The inherent accuracy of the roller screw and low backlash gearing provide repeatable positioning to within 0.005mm (5 microns), when the
actuator is combined with a suitable drive and control system. Ball screw models have a positional accuracy of 50 microns.
Guiding the Load
Side loads on the actuator ram should be avoided by ensuring that the load is guided. The load guide mechanism should resist the torque
developed at the ram by the screw mechanism, thus precluding the use of spherical end fittings. The guided ram option, which utilises
rolling element followers, eliminates the need for torsional restraint and therefore allows flexibility in the choice of end fittings.
Mounting Position
The Rolaram actuator can be mounted for operation in any orientation.
Safety Features
• In the event of power failure, the fail-safe brake on the motor will maintain the position
of the actuator
• Totally enclosed and sealed unit
• Built in proximity switches/limit switches
• Guided ram version
Operating Environment
All units are constructed and finished to suit industrial operating conditions. The actuator is sealed at the ram and including the standard
brake motor is protected to IP55 enclosure. Normal operating temperatures are from -10°C to +50°C. However, Power Jacks products have
been proven in very low operating temperatures (-30°C- Arctic) and in very high temperatures (+70°C- steelworks). Please contact our
Technical Sales Department to discuss hostile or hazardous operating environments.
Lubrication and Maintenance
Rolaram actuators require only a minimum of maintenance during the normal operating life. Depending upon the duty, periodic lubrication
should be carried out on the Spiracon roller nut, thrust housing and helical spur/spiral bevel gearbox, according to the application and our
recommended maintenance instructions.
Specials
The Rolaram concept has been successfully applied in many varied “special” applications, requiring for example:
•
Very high linear speed (over 50 metres/minute) or acceleration (over 3 metres/sec2)
• Very high dynamic load (over 1000kN)
• In-line drive configuration
• Special drive e.g inverter, servo, DC, stepper
• Temperature extremes or hazardous environment (e.g. subsea)
• Built in load cell
• Special mounting or restricted space
• Very low noise (under 60dB)