Double Chain Linear Actuator Helical Path Design
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Solution Overview
Problem
Conventional linear actuators with helically winding chains face limitations in side load stiffness and require oil, restricting their use in applications needing high side load capacity or where oil use is not permissible, and they often have a limited extended length to retracted length ratio due to the need for a planar chain track.
Innovation Solution
A double chain linear actuator design featuring helically winding chains with inter-connected links and a pivotal connection that allows for movement between extended and retracted positions without a planar chain track, utilizing a chain connecting member and drive mechanism to achieve a large extended length to retracted length ratio, good axial stiffness, and side load stiffness without oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a planar chain track is used to guide the chain, then the chain path is constrained and simple, but the extended length to retracted length ratio is limited
Solution Approach 1:
The patent transitions from a planar chain track (2D) to a three-dimensional helical chain path (3D). The chain is guided along a helical path within the actuator housing, allowing the chain to extend and retract in a coiled configuration. This dimensional change enables a much larger extended length to retracted length ratio because the chain can be stored in a compact helical form when retracted and fully extended when deployed, without requiring a long linear track.
2Length of moving object
If telescoping hydraulic jacks are used to achieve large extended length to retracted length ratio, then movement range increases, but side load stiffness deteriorates and oil is required
Solution Approach 1:
The patent replaces the hydraulic system (which uses oil and provides poor side load stiffness) with a mechanical chain drive system. The chain, driven by a motor and transmitted through gears and sprockets, provides the extending and retracting motion. This mechanical substitution eliminates the need for oil while maintaining good side load stiffness through the rigid chain links and their engagement with the sprockets, which can effectively resist lateral loads.
3Strength
If conventional chain actuators are used to achieve good side load stiffness, then side load capacity improves, but extended length to retracted length ratio is limited
Solution Approach 1:
The patent maintains the rigid chain structure with interconnected links that provide good side load stiffness, but reconfigures the chain path from planar to helical in three dimensions. The helical arrangement allows the chain to be compactly stored when retracted while still providing full extension when needed. The chain links remain rigid and engage with sprockets to maintain side load stiffness, while the helical path enables a much larger extension ratio compared to conventional linear chain actuators.
Data Source
AI summary
A linear actuator comprises a pair of chains. Each chain has a first link and a second link. The second link of each chain is adjacent to the first link of the chain. A pivotal connection pivotally connects the first and second links. The first link is pivotable about a pivot axis which is non-perpendicular to a longitudinal axis of the first link. A chain connecting member connects the chains at distal ends thereof. A drive mechanism moves the chains between an extended position and a retracted position. At least a portion of each chain is helically wound when the chains are in the retracted position.