Above video shows an Amacoil rolling ring linear drive in action. Its unique design makes it ideal for providing reciprocating motion without the need to reverse the drive motor.

Reversal in a rolling ring linear drive

In a rolling ring linear drive, such as the Model RG shown above, an assembly of three rolling ring bearings is positioned within the drive housing. Each ring in the assembly is set at an angle relative to the shaft to determine the traversing direction.

To reverse the traversing direction of the rolling ring drive, the entire rolling ring bearing assembly is pivoted to its opposite or "mirror" position on the shaft. The bearings' central ridge provides the pivotal point on which the rolling ring bearing assembly may be pivoted.

The process of pivoting the ring assembly is purely mechanical. On the bottom of the linear drive is a spring-actuated reversal mechanism. It is attached to the rolling ring bearing assembly. When the linear drive reaches the end of its stroke, end stops are used to trigger the reversal mechanism. When the reversal mechanism is triggered by contacting a stop, it pivots the rolling ring bearing assembly on the shaft so the rings assume the exact opposite angle on the shaft. The result is immediate, automatic reversal.

End stops can be screws, bolts, or even air cylinders. The stops may be positioned anywhere along the shaft length so that reversal occurs at the specific point desired.

The Model RS rolling ring linear drive does not have the auto-reverse feature making the RS better suited to positioning and other PLC-controlled applications.