With the Uhing model RG rolling ring linear drive, changes to travel direction and linear speed are both adjustable regardless of the rotational direction or speed of the drive motor. This purely mechanical control over travel direction and linear speed makes it easier to meet application requirements when compared to systems that require designing-in clutches, brakes, gearboxes, servo motors and complex control systems. It also minimizes operating and maintenance costs. And because rolling ring systems operate continuously even when changing direction or pitch, production rates and throughput improves.

A rolling ring linear drive is typically supplied within a production framework which is "dropped" into the manufacturing equipment. Adjustable end stops come installed on the assembly to control stroke length. When the linear drive traverses to the point where the mechanical reversal mechanism reaches an end stop, the reversal mechanism is turned and the drive reverses itself automatically.

Inexpensive and simple hardware modifications to the end stops and mechanical reversal mechanism, facilitate changes to the linear drive's travel direction and linear speed. This is useful to meet application requirements for ramping up/down and dwell. The most typical application requirements are:

Normally, the RG's reversal mechanism is actuated when it contacts an end stop, and automatic, instantaneous reversal occurs. Attaching the lever and modifying the end stops, however, permits controlled, slow rotation of the rolling ring bearing assembly within the housing or nut. The leading end of the lever contacts the end stop before the reversal mechanism does. The lever is turned and the rolling ring bearing assembly is partially rotated. That is, the bearings are slowly turned so they are more perpendicular to the shaft. This will decrease the drive's linear speed. If the bearings are moved so they are perpendicular to the shaft, the drive dwells on the shaft while the motor continues to operate.

Slow-down and ramp-up

To meet application requirements for deceleration (ramp-down) prior to reversal, and then acceleration (ramp-up) after reversal, the RG linear drive's end stops and reversal mechanism are modified as shown at right.

The lever is referred to as an "H-lever," and is connected through the housing to the rolling ring bearing assembly inside the drive box. As the drive traverses, the leading end of the H-lever contacts an end stop. As the lever is moved by the end stop, the bearing assembly is slightly pivoted which reduces the drive's linear speed.

Traveling at the reduced speed, the drive continues until the automatic reversal mechanism is tripped which causes reversal of travel direction. The trailing end of the H-lever then catches a second stop which prevents the rolling ring assembly from assuming its full pitch position. This causes the drive to travel back in the opposite direction - but at a reduced speed - until the trailing end of the H-lever gradually clears the stop to permit the rolling ring bearing assembly to assume its full pitch position, ramping the drive up to full linear speed.

Using the same lever attached to the reversal mechanism, the end stops may be slightly re-configured to make the RG linear drive decelerate to a point where the drive dwells until the reversal a mechanism is actuated. This variation is called a K-Stop. Illustrated at right is the K-Stop assembly.

When the rolling ring bearing assembly is perfectly perpendicular to the shaft, the linear drive has a pitch of zero. The drive then "dwells" on the rotating shaft with no linear movement until the ring assembly is again angled on the shaft. This is achieved by actuating the reversal mechanism either manually or pneumatically.

The K-Stop is only used when linear travel speed is less than 9 inches/sec. If the linear speed is greater, the drive is moving to fast for the K-Stop and instead of only partially turning the reversal lever, the K-Stop the lever would be completely flipped causing immediate reversal at full linear speed. At higher speeds, the V-Cam option is used.

A V-Cam is the simplest method of decelerating the RG rolling ring linear drive before reversal. As shown in the photo below, the V-Cam is a simple, V-shaped fixture mounted to the adjustable end stop. The V-Cam contacts the reversal mechanism and causes it to slowly turn - which pivots the rolling ring bearing assembly on the shaft. The linear drive's pitch is thereby gradually reduced, causing the linear speed to decrease.

By the time the linear drive reaches the end stop, and the reversal mechanism is fully flipped, linear speed is almost zero because the V-Cam has rotated the reversal mechanism to the point where the rolling ring assembly is almost at its zero pitch position. Deceleration in this manner, before reversal, permits any forward inertia of the payload to dissipate before the drive begins to traverse in the opposite direction.

Other rolling ring engineering motion control options:

Remote control of linear speed

The Z-option features a remote pitch (linear speed) control enabling rapid adjustments to the actuator's pitch (distance traveled per shaft revolution) while the system is in operation, without changing the drive motor rotational speed. The Z-control knob turns a worm gear affixed to the RG linear drive's pitch control mechanism to permit virtually infinite, on-the-fly fine tuning of pitch, bypassing the 100 discrete pitch settings (50 settings on older models) which are standard on the RG series linear drive. The Z-control lets users quickly adjust linear speed, without adjusting motor controls, simply by turning the pitch control knob.

Remote adjustment of reversal points

The position of the end stops, which control the reversal points, is also remotely adjustable. If the W Option is selected when ordering, the end stop assemblies are situated on threaded rods at the end of which are control knobs. Fine tuning of the linear drive's reversal points is possible simply by turning the control knobs until the end stops move to the desired position.

On-the-fly, automatic adjustment of stroke length and reversal points -- without programming or complex controls.

Mechanical controls enable automatic adjustment of the drive head (nut) stroke length and reversal points to meet application requirements. The assembly is designed for use in high volume production and assembly lines where it is necessary to gradually increase or decrease the drive head stroke length, without stopping or slowing down the system.

Typically, tools and payloads mount directly to the head (traversing nut) and do not require a separate load carrier. Example applications are loading/unloading machines, parts feeding systems, winding onto spools with outwardly tapered flanges, surface finishing systems, glue/adhesive application equipment, stirring/mixing processes, metrology procedures, and other applications requiring reciprocating linear motion.

The desired increase or decrease in stroke length is set via a control knob on the front of the assembly. As the system operates, a ratchet lever attached to the framework is actuated when the linear drive passes by causing the "end stops" to automatically move apart or together in increments relative to the dialed-in value. The end stops trigger the spring-actuated reversal mechanism on the rolling ring linear drive so, as the end stops change position, the drive head's stroke length and reversal points change accordingly. Because the changes are made while the system is in operation, independently of the drive motor's speed and rotational direction, the need for clutches, gears and complex control systems is eliminated, permitting the use of an affordable unidirectional, single speed motor to drive the system.