Linear Actuator Rotary Lock Assembly Design
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Solution Overview
Problem
Conventional linear actuators face issues with indirect locking mechanisms, increased size and mass, fatigue concerns, and low external load carrying capability due to point contact stresses, as well as the need for separate electrical or mechanical inputs for unlocking.
Innovation Solution
A rotary lock mechanism with axially fixed lock keys that engage a radial groove in the output ram, allowing direct locking and unlocking without additional commands, using a single-piece housing and a rotor with radial grooves to restrain the lock keys, enabling secure axial locking and unlocking via rotational positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-piece housing with direct locking mechanism is used, then locking capability is improved, but size and mass increase
Solution Approach 1:
The locking mechanism is segmented into modular components: a rotor with radial grooves, lock keys with crowns, and a single-piece housing. This segmentation allows each component to perform its specific function efficiently while keeping the overall structure compact and lightweight, resolving the contradiction between locking capability and mass.
Solution Approach 2:
The lock keys are nested within the rotor structure, with the crowns of the lock keys fitting into radial grooves of the rotor. This nesting arrangement maximizes space utilization, allowing the locking mechanism to be compact without compromising its load-bearing capability, thus reducing size and mass while maintaining reliability.
2Ease of manufacture
If a flexing lock element is used to allow single-piece housing, then manufacturing complexity is reduced, but fatigue reliability deteriorates
Solution Approach 1:
Instead of making the housing flexible to accommodate the locking mechanism, the invention inverts the approach by making the locking elements (lock keys and rotor) the flexible/adaptable components. The lock keys can shift position within the rotor grooves, providing the necessary flexibility without requiring a multi-piece housing, thus achieving both ease of manufacture and fatigue resistance.
3Ease of operation
If ball lock mechanisms are used, then locking simplicity is improved, but external load carrying capability deteriorates due to point contact stresses
Solution Approach 1:
The invention transitions from point contact (ball locks) to line contact by using radial grooves in the rotor that engage with the crowns of the lock keys. This dimensional change from zero-dimensional point contact to one-dimensional line contact significantly increases the surface area over which loads are distributed, thereby enhancing external load carrying capability while maintaining locking simplicity.
4Reliability
If a rotary-to-linear motion conversion mechanism is used for lock sleeve, then locking functionality is achieved, but device complexity increases
Solution Approach 1:
The rotor itself serves the dual function of both the locking mechanism and the motion conversion device. As the rotor rotates, its radial grooves automatically guide the lock keys into the appropriate positions, eliminating the need for a separate rotary-to-linear motion conversion mechanism. This self-service approach achieves locking functionality while minimizing device complexity.
Data Source
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AI summary
A linear actuator (100) includes a housing, a linear output member, and a rotary lock assembly. The linear output member includes a radial groove and is axially movable from a retracted position within the housing. The rotary lock assembly (112) is constrained from axial motion within the housing (104) and includes a rotor (116) and a lock (120). The rotor is capable of rotation from a first to a second position. When the linear output member is in the retracted position, the rotor surrounds the radial groove. When the rotor rotates to the first position, the lock engages the radial groove and prevents axial motion of the output member from the retracted position.