MOTION SYSTEMS HANDBOOK
Chain actuation — rigid type
Linear actuators abound but some
Common rigid-chain arrangements
applications need telescoping actuators — mechanical linear-motion devices that extend
Chain link shoulders
into a volume beyond the machine base, drive housing, and guides. There are many variations, but the most common telescoping actuators are based on interlocking segments
Unguided chain with shoulders up coils downwards ...
of rigid chain; advancing spirals of helical band; segmented-cylinder spindle sets; and zipper-type mating belts. In one way or another, all extend the linkages or coils into
... but guided chain is most stable.
rigid columns that mechanically lock into a
Actuator body
column that advances, pulls, or lifts loads. Rigid-chain actuators work by pairing a drive (usually an electric motor) with a length of chain sporting shoulders on each link. The motor output shaft—fitted with a specialty sprocket or pinion—applies tangential force to the chain. Then the chain comes out and straightens, and its links’ shoulders lock to form a rigid series. When the motor runs in the opposite direction, the chain shoulders disengage and allow for coiling. Inside the actuator body, reaction plates and guides counter thrust resistance and keep the chain on track. Links travel around the pinion to exit the actuator body along the stroke path. Here, the motor’s torque comes to act as forward thrust via the link shoulder to the rest of the links’ shoulders. The last link in
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DESIGN WORLD — MOTION
Chain Actuation — Motion Control HB 08-19 V3.indd 22
Pinion Input drive shaft Choose a rigid-chain actuator to satisfy the design geometry.
Unguided chain with shoulders up coils downwards, which is useful but not always stable enough for long strokes. That with shoulders down (here, bottom) is slightly more stable. Use guided chain wherever space permits.
8 • 2019
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8/15/19 1:56 PM
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