Linear Drive

HIGH SPEED - SMOOTH SPEED CONTROL Controlled acceleration and deceleration ... with the Flo-Tork rotary actuator rotating at a constant speed. You can go faster and smoother using rotary actuators than with any other method.

Linear Drive with Flo-Tork Rotary Actuators Using Harmonic Motion

The advantages of using rotary actuators, combined with harmonic-motion-producing linkages, compared to straight line cylinders, are derived from the principle of converting a constant speed rotating motion to a sinusoidal (sine-wave) motion which produces maximum linear force where needed for acceleration ... and just the opposite force for deceleration and stopping the load. Meanwhile, you develop maximum linear speed during the middle of the 1800 rotation cycle.

Acceleration control is easy to achieve and usually is limited only by the available hydraulic or pneumatic power.

Deceleration is usually the big problem and the speed of any reciprocating or oscillating motion is normally limited by the ability to control deceleration. Deceleration valves are expensive, difficult to field-adjust and susceptible to tampering and to malfunction from contaminated oil or air.

A simple flow control valve to maintain constant speed of the rotary actuator can, when combined with the harmonic linkage, decelerate the load smoothly to rest.

GENTLE ACCELERATION You have the maximum mechanical advantage where you need it ... at the beginning of the travel. Force arrow shows maximum force in the direction of start-up to get you started faster.

SPEED Maximum velocity is when the load is half-way to its destination. Smooth acceleration to that point ... then smooth deceleration.

How to Size Flo-Tork Rotary Actuators for Moving Loads in a Linear Direction Assuming the Harmonic Motion Principle

Two factors are required before you can size any drive which is moving a load horizontally:

1. Force required to accelerate and decelerate the load.
2. Force required to overcome friction losses in the system.

Two curves have been developed for you to use as guide lines for your particular design needs.

The low friction curve can be used to select the maximum torque required to transfer a given load, a given distance, in a given time for low to moderate friction arrangements such as ball bearings, rollers, etc. (assuming a coefficient of friction of 0.05).

The high friction curve is derived in the same way for moderate to high friction arrangements such as journal bearings, slides, etc. (assuming a coefficient of friction of 0.25).

Since it is not convenient to reverse the pressure system at mid-travel to provide deceleration torque, it is simpler to use a torque value of double the acceleration torque and apply flow-control to the discharge ... in other words, a metering-out system. This assures a positive pressure system at all points and gives a simple and positive control system. Our curves include that safety factor.

GENTLE DECELERATION You have the maximum mechanical advantage where you need it ... at the end of the travel. Deceleration is a "mirror" reflection of acceleration and the load will be slowed down by the rotary actuator automatically.