Linear Actuator Hollow-Shaft Layout for Shorter Retracted Length
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Solution Overview
Problem
Existing electromechanical linear actuators have a large axial design space requirement due to the adjacent arrangement of the electric motor and threaded nut, leading to a significant axial length in the maximally retracted state.
Innovation Solution
The arrangement of a holding brake and a first rotary bearing within the hollow shaft of the electric motor, along with a second rotary bearing between the housing and the hollow shaft, allows for a compact design by positioning these components on the inner circumference of the hollow shaft, minimizing the axial design length. Additionally, a screw support and transmission within the hollow shaft enhance the actuator's functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the holding brake and first rotary bearing are arranged within the hollow shaft, then the axial design length is minimized, but the device complexity increases
Solution Approach 1:
The holding brake and first rotary bearing are nested within the hollow shaft of the electric motor, placing one component inside another to achieve compact axial arrangement. This nesting principle allows multiple components to occupy the same axial space, minimizing the overall axial design length while containing the increased component density within the hollow shaft structure.
Solution Approach 2:
The design transitions from a linear axial arrangement to a radial arrangement within the hollow shaft. By positioning the holding brake and first rotary bearing radially within the hollow shaft's cross-section rather than extending them axially, the solution exploits the radial dimension to reduce the axial footprint, effectively moving the problem from one dimension to another.
2Power
If the electric motor and threaded nut are arranged adjacently, then the torque transfer is effective, but the axial design space requirement increases
Solution Approach 1:
The threaded nut is positioned to overlap radially with the hollow shaft of the electric motor, with the ball screw passing through both the hollow shaft and the threaded nut. This radial nesting arrangement allows the torque transfer path to remain direct and effective while eliminating the need for axial separation between the motor and threaded nut, thereby reducing the axial design space requirement.
Solution Approach 2:
The design shifts from an axial arrangement where the motor and threaded nut are positioned end-to-end to a radial arrangement where they overlap in the same axial space. By utilizing the radial dimension for component placement, the solution maintains effective torque transfer through the ball screw while minimizing the axial footprint of the overall assembly.
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
This configuration minimizes the axial design length of the electromechanical linear actuator in the maximally retracted state, providing a more compact and efficient design suitable for various applications, such as excavator arms or telescopic handlers, while maintaining effective torque transfer and position determination without additional distance measuring systems.
Implementation Method 1
a holding brake for the lead screw
Implementation Method 2
a first rotary bearing for bearing the lead screw on a housing of the linear actuator
Data Source
AI summary
An electromechanical linear actuator having a threaded drive, which comprises a threaded nut connected to a cantilever tube and a lead screw connected to a hollow shaft of an electric motor via a rotationally fixed connection in such a way that, by a rotation of the hollow shaft and the lead screw, the threaded nut and the cantilever tube are linearly movable. An axial design length of the electromechanical linear actuator in the maximally retracted state is minimized in that a holding brake for the lead screw and a first rotary bearing for bearing the lead screw on a housing of the linear actuator are arranged within the hollow shaft.