Linear Actuator Anti-Rotation Structure for Even Stress Distribution
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Solution Overview
Problem
Prior art linear actuators with intertwined bands suffer from uneven distribution of mechanical stresses due to punctual abutment of teeth on anti-rotation rollers, leading to undesirable tangential and radial forces on the column.
Innovation Solution
An anti-rotation mechanism with non-punctual engagement of first and second anti-rotation members, such as teeth on the band and grooves on the base, prevents rotation of the extractable and retractable column by distributing the abutment evenly around the periphery, using a ring with grooves for sliding engagement of teeth parallel to the longitudinal axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If anti-rotation rollers are used to prevent column rotation, then rotation prevention is achieved, but uneven distribution of mechanical stresses occurs due to punctual abutment
Solution Approach 1:
The anti-rotation mechanism is segmented into multiple discrete teeth on the band and multiple corresponding grooves on the base. Instead of a single continuous contact surface, the anti-rotation function is distributed across multiple discrete engagement points arranged circumferentially around the column, transforming punctual stress into distributed stress across multiple locations.
Solution Approach 2:
The engagement interface transitions from a punctual (zero-dimensional point contact) or linear (one-dimensional line contact) interaction to a two-dimensional area contact. The grooves on the base provide a surface area for tooth engagement rather than a single roller contact point, distributing stress across a larger dimensional footprint in the radial plane.
2Stability of the object's composition
If teeth on the band engage with anti-rotation rollers, then rotation is prevented, but tangential and radial forces concentrate at specific points
Solution Approach 1:
The force transmission path is segmented into multiple discrete tooth-groove engagement pairs distributed around the column circumference. Each tooth engages with a corresponding groove to share the load, preventing force concentration at a single roller contact point and distributing tangential and radial forces across multiple locations.
Solution Approach 2:
The grooves on the base provide localized engagement surfaces at specific circumferential positions, creating zones of concentrated force resistance that collectively distribute the overall load. Each groove is positioned to receive and distribute forces locally, with the cumulative effect being even global force distribution across the column perimeter.
3Ease of operation
If punctual abutment of teeth on rollers is used, then anti-rotation function is achieved, but undesirable stress concentrations occur
Solution Approach 1:
The simple anti-rotation concept of tooth-roller contact is segmented into tooth-groove contact, where multiple grooves replace a single roller. This maintains the simplicity of the engagement mechanism while distributing stress uniformly, as each groove provides a localized engagement zone that collectively achieves even stress distribution across all teeth.
Data Source
AI summary
The linear actuator comprises elongated first and second bands that cooperate to form an extractable and retractable column. Rotatable first and second band guide members respectively guide turns of the first and second bands into intertwined engagement. A power actuator causes rotation of the first and second band guide members such that the extractable and retractable column may be extracted or retracted. A base carries the power actuator, the first and second bands and the first and second band guide members. An anti-rotation mechanism comprises a first anti-rotation member attached to the base and a complementary second anti-rotation member attached to at least one of the first and second bands, with the first and second anti-rotation members engaging one another in the column to prevent rotation of the column relative to the base. The engagement of the first and second anti-rotation members is non-punctual about a periphery of the column.