Compact inverted roller screws

Inverted roller screws I-R
The SKF compact inverted roller screw represents a unique design variant of the planetary roller screw. This design provides powerful electromechanical actuation, when compactness and high load capability are prerequisites.
The compact inverted roller screw works on the same principle as a planetary roller screw, with the roller's rotation being synchronized with the threaded shaft through toothed rings. Either nut or shaft can be driven by an electric motor, the non-rotating component thus acting as the rod of an actuator. The application loads acting on the translating rod transit through the planetary rollers to the rotating shaft or nut. Toothed rings and guides ensure the rolling motion and an even circumferential position of the rollers, for perfect load distribution and to eliminate any parasitic friction between rollers.

Features and benefits

  • Stroke depending on nominal diameter. Please consult SKF
  • Standard lead precision G5 (ep=25µm/300mm)
  • High rotational speed depending on screw nominal diameter: N.d0 max = 160000
    (for example,  4100 RPM for screws with nominal diameter 39 or 8888 RPM for screws with nominal diameter 18 mm; could be higher for smaller size shaft. Please consult SKF)
  • ISR version with axial play
  • IBR with backlash elimination by oversized rollers
  • Very small lead down to 2,4 mm, while providing a high load carrying capacity and high axial stiffness  (for smaller leads please consult SKF)
  • High speed capability
  • Guiding and sealing functions easily integrated on smooth surface of nut or shaft, resulting in high performance sealing
  • Compactness, low weight and reduced number of parts in overall customer system
  • Customized attachment between electric rotor and screw components, and easy rotor integration
  • Screw or nut directly used as push tube of the actuator
  • Reduced requirements for electric motor torque to reach high load actuation
  • Long service life and increased reliability improving customer installation productivity
  • Availability of customized designs
  • Low backdriving ability and even self locking solutions are possible

Technical data of the ISR / IBR standard range

Nominal diameter
from 18 to 48 mm
from 2,4 to 6 mm
Basic dynamic load capacity
up to 259kN
Basic static load capacity
up to 559 kN
up to 12 000 rad/s2

Typical applications

  • Electromechanical cylinders
  • Car assembly lines (spot welding, gluing, crimping, riveting etc.)
  • Factory automation
  • Oil and gas
  • Aerospace
  • And many other applications

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