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by Carl Erickson 7 years, 8 months ago
Telescoping Linear Actuators are specialized linear actuators used where space restrictions exist. They begin in compact spaces and can extend into a rigid body that is many times longer than the unstretched length of the member. The most common form is the telescoping cylinder where concentric tubes of equal length extend and retract like sleeves. Here are some alternatives:
Helical Band Actuator (perpendicular interlock)
This actuator works using a pair of interlocking stainless steel bands. One band has a vertical profile and the other has a horizontal profile. The vertical band spirals up into a stack helix forming the wall of the column, while the horizontal band interlocks the spiral seam of the vertical band. The two bands retract and separate into two compact coils when the column lowers. Helical band actuators are used in stage lifts and material handling lifts. The actuators are controlled by an electric motor below the lift platform. These actuators can form high-capacity tubular columns that can lift up to 25,000 lbs travel to 40 ft.
Helical Band Actuator (parallel interlock)
Three stainless steel strips are brought into parallel (face-to-face) contact form the walls of this helical actuator. Bearing balls caged along the center length of the inner strip engage helical grooves of the drive mechanism (much like a thrust bearing) to propel the column. The type of (jigsaw puzzle piece) strip interlock employed distributes load forces evenly which allows for the use of thin strip materials (down to 0.1mm). Though suitable for use as a lift column, the unique properties of these actuators are best applied to complex load conditions such as in tetrahedral robots or deploy-able structures.
Rigid Belt Actuator
In this actuator, a belt and pinion device forms a telescoping beam to transmit traction and thrust. They use two ribbed belts that engage with pinions mounted on the drive shafts within a housing. When the pinions spin, the belts are rotated 90 degrees through the housing which interlocks the blocks like a zipper into a rigid linear form. The unfolded beam can be stored compactly in a storage magazine. This actuator is usually used in push-pull and lift applications and can move up to 230 lbs over 3 ft of travel.
Rigid Chain Actuator
Similar to the belt actuator, this actuator uses a pinion and chain device. It uses limited-articulation chains that engage with pistons on a drive shaft within a housing. The links of the rigid member are articulated in a manner that they deflect from a straight line to one side only. As the pinions spin, the links of the spin are rotated through the housing which guides and locks the chain into a rigid linear form. Rigid chain actuators are used in window operating and lifting applications and can move loads of 10 tons over 20 ft.
Coiled Tape
Three strips interlock in a triangular configuration to form a column from separately spooled material.
Segmented Spindle
This is a specialized mechanical linear actuator. It forms a telescoping tubular column from linked segments resembling curved parallelograms. It has a lifting capacity of up to 440 lbs and 15.75 inches. A short elongated housing forms the base of the actuator and includes an electrical gear drive and storage magazine. The drive spins a helically grooved wheel that engages the spindle segments. As the wheel spins it simultaneously pulls the segments form the horizontal arrangement in the magazine and stacks them along the vertical path of a helix into a rigid tubular column.
Slit Tube
A bi-stable metal band transitions between flat and bent states as it enters/exits its spool. The bent state band wraps around to join itself in so forming a tube.
Slit Tube (2)
A bi-stable metal band transitions between flat and bent states as it enters/exits its spool. The bent state band wraps around to join itself in so forming a tube.