Wobble Joint Linear Actuator for High-Load Misalignment
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Solution Overview
Problem
Existing screw-type linear actuators, such as ball screws, face misalignment issues under high axial loads due to friction, which causes the joint to lock up before reaching full working load and results in deflection.
Innovation Solution
A screw-type linear actuator design featuring a support structure with a screw shaft that is axially stationary but rotatably drivable, incorporating a nut with a spherical profile annular contact surface and a thrust flange with an offset annular contact surface, along with a thrust bearing between the thrust flange and the support structure, to mitigate misalignment and enhance load handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spherical wobble joint with cone contact is used to accommodate misalignment, then the actuator can handle axial loads, but friction causes the joint to lock up before full working load is reached
Solution Approach 1:
The patent employs a spherical contact surface on the wobble joint that engages with a corresponding spherical surface on the thrust flange, replacing the conventional cone contact. This spherical geometry allows for smooth rotation and misalignment accommodation while distributing contact stresses more evenly, preventing friction-induced lockup and enabling the joint to operate through the full range of motion under high axial loads.
2Stress or pressure
If the contact surface radius is increased to reduce contact stress, then load distribution improves, but the joint becomes more complex and larger
Solution Approach 1:
The patent integrates the thrust flange directly with the wobble joint assembly, combining the thrust bearing support function with the misalignment accommodation function into a single unified structure. This merging eliminates the need for separate components, reducing overall complexity while maintaining the beneficial large-radius spherical contact surfaces that distribute load and reduce contact stress.
3Force
If a thrust bearing is added to support axial loads, then load capacity increases, but the device complexity and number of components increase
Solution Approach 1:
The thrust flange in the patent serves multiple functions simultaneously: it provides the spherical contact surface for misalignment accommodation, supports axial thrust loads through its bearing surface, and integrates with the wobble joint rotation mechanism. This multi-functionality eliminates the need for separate thrust bearing components while maintaining high axial load capacity, thereby reducing device complexity.
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 design allows for improved axial movement and load distribution, reducing stress and enabling smoother operation under high loads by allowing for controlled misalignment and even loading of the thrust bearing, thus preventing joint lockup and enhancing the actuator's performance.
Implementation Method 1
the screw shaft defines a first annular contact surface having a spherical profile with a first radius. A thrust flange is located on the screw shaft for rotation with the screw shaft, the thrust flange having a second annular contact surface with a second radius, the first annular contact surface engaging the second annular contact surface.
Data Source
AI summary
A screw-type linear actuator comprises a support structure and a screw shaft that is axially stationary with respect to the support structure but rotatably drivable. A nut is mounted on the screw shaft such that rotation of the screw shaft causes axial movement of the nut along the screw shaft. In addition, the screw shaft defines a first annular contact surface having a spherical profile with a first radius. A thrust flange is located on the screw shaft for rotation with the screw shaft, the thrust flange having a second annular contact surface with a second radius, the first annular contact surface engaging the second annular contact surface.