Linear Actuator Shaft Detents for Compressive Load Locking
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Solution Overview
Problem
Existing linear actuators with compressive loads, such as those in power door opening systems, face inefficiencies due to complex mechanically gated locks and require significant force to maintain position against compressive loads, which can lead to mechanical stress and inefficiency.
Innovation Solution
A simplified locking mechanism using detents on the screw shaft in the form of grooves that cooperate with rollers to prevent axial movement, allowing the nut to be locked in place without the need for complex mechanical locks, and a variable lead angle screw thread tailored to the load profile to optimize movement under compressive loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex mechanically gated lock is used to secure the actuator output, then the locking reliability is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the locking function from a complex mechanically gated lock system and implements it through simple detents integrated directly into the screw shaft. The detents work with rollers on the nut to provide locking at specific axial positions, eliminating the need for complex gating mechanisms while maintaining reliability.
Solution Approach 2:
The detents on the screw shaft automatically engage with the rollers on the nut to provide locking functionality. The system uses its own operational components (screw shaft and nut) to provide the locking function, rather than requiring separate complex locking mechanisms.
2Ease of manufacture
If a constant lead angle screw thread is used, then the manufacturing simplicity is improved, but the efficiency under varying compressive loads deteriorates
Solution Approach 1:
The patent applies different lead angles at different axial locations along the screw shaft. The lead angle is varied to match the compressive load profile, with smaller lead angles where loads are higher and larger lead angles where loads are lower. This local variation optimizes efficiency for each specific operational condition.
Solution Approach 2:
The lead angle parameter of the screw thread is changed along the axial direction to optimize performance. The variable lead angle allows the screw thread to adapt to varying compressive loads, improving overall actuation efficiency compared to a constant lead angle design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a non-complex locking mechanism that effectively prevents axial movement under compressive loads, reducing mechanical stress and improving efficiency by allowing the nut to be securely locked and easily moved with controlled rotational forces, while the variable lead angle optimizes force requirements based on load distribution along the actuator.
Implementation Method 1
a screw shaft (12) comprising a screw thread (14)
Implementation Method 2
a plurality of rollers (20) arranged on the nut (30), each roller (20) configured to engage a respective flank (16, 18) of the screw thread (14)
Data Source
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AI summary
There is disclosed a linear actuator (10) comprising: a screw shaft 12 comprising a screw thread 14 and having a longitudinal axis A; a nut 30 movable along the screw shaft 12 from a retracted position to an extended position; and a plurality of rollers 20 movable with the nut 30, each comprising a cylindrical surface 21 configured to roll along one or more flanks 16,18 of the screw thread 14, such that rotation of the screw shaft 12 causes the rollers 20 to roll along the flank(s) 16,18 so that the nut 30 translates in an axial direction along the screw shaft 12; wherein the screw thread 14 comprises one or more detents (e.g., grooves 50) configured to lock the nut 30 in one or more axial positions.