Linear Actuator Squeeze Protection Using Ring-Shaped Piezo Element
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Solution Overview
Problem
Existing linear actuators in adjustable furniture lack effective protection against squeeze injuries and damage from collisions with inflexible objects during adjustment, as they do not adequately sense and respond to obstacles.
Innovation Solution
A ring-shaped piezo element with a through-going hole is integrated into the spindle unit, mounted using double adhesive tape, which senses bending forces and triggers the motor to stop or reverse when a predetermined force threshold is exceeded, preventing damage and injury.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezo element is placed in connection with a bearing for the spindle, then squeeze protection function is provided, but the placement arrangement is not specified and signal quality is insufficient
Solution Approach 1:
The piezo element is positioned at a specific location in the force transmission path where it optimally detects collision forces. The ring-shaped configuration and placement in connection with the bearing ensure the element experiences maximum stress during squeeze events, improving detection reliability while maintaining compact dimensions.
2Ease of manufacture
If a ring-shaped piezo element is used, then ease of mounting and signal/noise ratio are improved, but the structural complexity increases
Solution Approach 1:
The piezo element is designed as a ring-shaped component with a through-going hole, segmenting the structure to allow direct mounting on the spindle or bearing. This segmentation enables easy installation by simply placing the ring around the spindle shaft, eliminating complex fastening procedures while maintaining structural integrity.
Solution Approach 2:
The ring-shaped piezo element with through-going hole is designed to fit over the spindle, creating a nested arrangement where the piezo element encompasses the spindle. This nesting approach simplifies mounting as the element slides onto the existing spindle structure without requiring additional fasteners or complex assembly steps.
3Object-affected harmful factors
If the piezo element detects collision forces, then safety protection is provided, but the actuator may stop or reverse causing additional harm
Solution Approach 1:
The piezo element continuously monitors forces in the force transmission path and provides real-time feedback to the control system. When collision forces exceed a predetermined threshold, the feedback signal triggers the control system to stop the motor, preventing both squeeze injuries and potential reversal damage.
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 solution provides enhanced safety by effectively preventing squeeze injuries and damage by accurately detecting collisions and controlling the motor to avoid obstacles, offering a superior signal/noise ratio and ease of mounting.
Implementation Method 1
a piezo element for registering forces in the force transmission path
Data Source
AI summary
A linear actuator especially for adjustable furniture comprises a spindle (16) with a spindle nut (16a) for bringing about the adjustment of the article of furniture. At the end of the spindle (16) there is a bearing (17) for mounting of this in the actuator. The spindle/spindle nut (16,16a) is driven by an electric motor (27) through a transmission (28). For preventing accidents and/or damage during the adjustment of the article of furniture the actuator is equipped with a squeeze protection based on a piezo element (22). This piezo element (22) is arranged in connection with the bearing (17) for registering the forces or deflections of the forces affecting the spindle (16). In that the piezo element (22) has a through-going hole for the spindle the mounting of the piezo element (22) is simplified and further it has turned out that a particularly good signal/noise ratio is obtained.