Linear Actuator Thread Detents for Compressive Load Locking
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Solution Overview
Problem
Existing linear actuators with compressive loads, such as power door opening systems, face inefficiencies due to complex mechanically gated locks and require significant mechanical components, which can be cumbersome and prone to failure under constant axial forces.
Innovation Solution
A linear actuator design featuring a screw shaft with a variable lead angle and rollers that interact with detents in the form of grooves to provide a simple and effective locking mechanism, allowing the nut to translate axially while preventing axial forces from retracting the nut, thereby eliminating the need for complex locks and optimizing load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex mechanically gated lock is used to secure the actuator output, then the actuator can be locked at discreet axial positions, but the device complexity increases and the reliability decreases due to numerous moving parts
Solution Approach 1:
The patent extracts the locking function from a separate complex mechanically gated lock system and integrates it directly into the screw thread structure through detents. This eliminates the need for numerous moving parts in a separate locking mechanism while maintaining the ability to secure the actuator output at discreet axial positions.
Solution Approach 2:
The patent merges the locking function with the screw thread structure by incorporating detents directly into the thread geometry. This combination eliminates the need for a separate locking mechanism and reduces the number of moving parts, thereby simplifying the overall device structure while maintaining reliability.
2Reliability
If a mechanically gated lock with numerous moving parts is used, then the actuator can be secured at axial positions, but the loss of time increases due to more parts that can fail and require maintenance
Solution Approach 1:
The patent removes the time-consuming elements associated with complex locking mechanisms by extracting the locking function and implementing it through simple detents in the screw thread. This eliminates the need for maintenance and reduces downtime while maintaining the ability to secure the actuator at required positions.
3Productivity
If a standard lead angle screw thread is used, then the nut can translate along the screw shaft, but the efficiency decreases under compressive loads as seen in power door opening systems
Solution Approach 1:
The patent applies local quality by varying the lead angle of the screw thread at different axial positions. The lead angle is optimized for each specific section to match the local load conditions, thereby improving efficiency under compressive loads while maintaining the ability to translate the nut along the screw shaft.
Solution Approach 2:
The patent changes the geometric parameter of the screw thread by implementing a variable lead angle instead of a constant one. This parameter change allows the screw thread to adapt to varying load conditions along its length, improving overall system efficiency and reducing energy loss under compressive loads.
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 manages compressive loads, reduces mechanical complexity, and optimizes the actuator's performance by tailoring the lead angle to match the load profile, enhancing reliability and efficiency in systems like power door opening systems.
Implementation Method 1
The plurality of rollers each comprise a cylindrical surface configured to roll along one or more flanks of the screw thread, such that rotation of the screw shaft causes the rollers to roll along the flank(s) so that the nut translates in an axial direction along the screw shaft
Implementation Method 2
Each detent may be provided in the form of a groove configured to receive one of the plurality of rollers. Each groove may have a profile that prevents a respective roller from rolling back onto the screw thread upon application of a force to the nut in the axial direction
Data Source
AI summary
A linear actuator includes: a screw shaft that has a screw thread and a longitudinal axis A and a nut movable along the screw shaft from a retracted position to an extended position. The actuator also includes a plurality of rollers movable with the nut, each of which includes a cylindrical surface configured to roll along one or more flanks of the screw thread, such that rotation of the screw shaft causes the rollers to roll along the flank(s) so that the nut translates in an axial direction along the screw shaft. The screw thread includes one or more detents (e.g., grooves) configured to lock the nut in one or more axial positions.