Hollow-Shaft Linear Actuator for Reduced Axial Installation Space
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Solution Overview
Problem
Existing electromechanical linear actuators have a large axial installation space requirement due to the arrangement of the electric motor and threaded nut, which limits the maximization of the length ratio between the extended and retracted states.
Innovation Solution
The electromechanical linear actuator incorporates a threaded drive with a threaded spindle coupled to a hollow shaft of an electric motor via a rotationally fixed connection, and a threaded nut fastened to a linearly movable extension tube. In the retracted state, the threaded nut is enclosed within the hollow shaft, minimizing axial installation space and maximizing the length ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the electric motor and threaded nut are arranged adjacent to each other in the axial direction, then the linear actuator can be compact, but the axial installation space requirement becomes large
Solution Approach 1:
The threaded nut is nested inside the hollow shaft of the electric motor when the extension tube is in the retracted position. This nesting arrangement allows the threaded nut to be accommodated within the hollow shaft's internal volume, eliminating the need for additional axial space for the threaded nut and thereby reducing the overall axial installation space requirement.
Solution Approach 2:
The invention transitions from a conventional axial arrangement where the threaded nut is positioned outside the motor to a radial arrangement where the threaded nut is positioned inside the hollow shaft. This dimensional change from external axial placement to internal radial placement optimizes the axial length while maintaining functional requirements.
2Ease of operation
If the threaded spindle is exposed, then it is accessible for operation, but it becomes vulnerable to dirt and mechanical damage
Solution Approach 1:
The extension tube acts as a protective shell that encloses the threaded spindle when retracted. This tubular protection prevents dirt, debris, and mechanical damage from reaching the threaded spindle while still allowing the assembly to function properly when extended.
Solution Approach 2:
The extension tube dynamically changes position between extended and retracted states. When retracted, it provides protection; when extended, it allows operation. This dynamic positioning enables the system to switch between protection and accessibility modes as needed.
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 effectively reduces the axial installation space requirement, maximizes the length ratio between the extended and retracted states, and protects the threaded spindle from dirt and mechanical damage using the extension tube.
Implementation Method 1
an electric motor (3), viewed in the axial direction, has a hollow shaft (1)
Implementation Method 2
a threaded drive that has a threaded spindle (7) and a threaded nut (8)
Data Source
AI summary
An electromechanical linear actuator includes a threaded drive which has a threaded spindle and a threaded nut. The threaded spindle is coupled to a hollow shaft of an electric motor via a rotationally fixed connection. The threaded nut is fastened to a linearly movable extension tube. In a maximally retracted state of the extension tube, the threaded nut is retracted at least in portions, preferably completely, into the interior of the hollow shaft. During operation of the linear actuator, the threaded spindle rotates and is not moved linearly. The threaded nut does not rotate and is moved linearly.