Height-Adjustable Table Bracket with Piezoelectric Squeeze Protection
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Solution Overview
Problem
Existing height-adjustable tables lack effective and integrated squeeze protection mechanisms that can reliably detect collisions from any direction, leading to potential personal injury and damage, as current solutions are either complex, expensive, or inefficient in registering torque and force loads.
Innovation Solution
A squeeze protection device incorporating a piezo element in a bracket that connects the table top to the adjustable column, which generates a voltage pulse upon bending, allowing for sensitive detection of collisions irrespective of their location, with a two-piece structure and spring mechanism to filter and scale signals, ensuring minimal false triggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motor current measurement is used for squeeze protection, then personal injury protection is improved, but the solution only detects extensive squeezing and not minor collisions
Solution Approach 1:
The patent replaces motor current measurement with a piezoelectric sensor that directly measures mechanical force/collision events. The piezoelectric element generates an electrical charge in response to applied mechanical stress, enabling detection of both minor collisions and major squeezing events with high precision across the full range of force magnitudes.
Solution Approach 2:
The patent changes the measurement parameter from motor current (indirect measure of load) to piezoelectric charge output (direct measure of applied force). This parameter change enables detection of the full spectrum of collision forces, from minor impacts to major squeezing events, resolving the sensitivity limitation of current-based detection.
2Measurement precision
If load cells in U-shaped profiles are used, then force measurement is improved, but torque loads create measurement errors and reduce detection reliability
Solution Approach 1:
The patent extracts the force measurement function from the structural U-shaped profile and places it in a dedicated piezoelectric sensor mounted on the bracket. This separation allows the sensor to measure only the collision force component perpendicular to the bracket, eliminating interference from torque loads that act on the profile structure.
Solution Approach 2:
The piezoelectric sensor acts as an intermediary between the collision event and the measurement system. It converts mechanical force directly into an electrical signal, isolating the measurement from the complex stress states (including torque) present in the bracket structure, thereby improving detection reliability.
3Reliability
If piezoelectric sensors are mounted on moveable parts, then collision detection is improved, but the solution requires high force to detect collisions and is sensitive to torque loads
Solution Approach 1:
The patent pre-loads the piezoelectric sensor through the spring mechanism, which applies a constant compressive force to the element. This preliminary action sensitizes the sensor to detect even minor additional forces from collisions, as the sensor operates in a region of high differential sensitivity where small force changes produce measurable signal variations.
Solution Approach 2:
The patent changes the operational state of the piezoelectric sensor from an unloaded or lightly-loaded state to a pre-compressed state. This parameter change optimizes the sensor's sensitivity to small force variations, enabling detection of minor collisions with low force thresholds while the spring mechanism filters out high-frequency noise and torque interference.
4Device complexity
If squeeze protection devices are integrated into the bracket structure, then device complexity is reduced, but the solution must filter out non-relevant dynamic forces to avoid false triggers
Solution Approach 1:
The patent uses a spring mechanism to cushion and filter dynamic forces before they reach the piezoelectric sensor. The spring absorbs high-frequency vibrations and transient loads that would otherwise cause false triggers, while still transmitting genuine collision forces to the sensor. This beforehand cushioning improves reliability by reducing false alarms.
Solution Approach 2:
The spring acts as a mechanical intermediary between the bracket structure and the piezoelectric sensor. It selectively transmits force components relevant to collision detection while filtering out non-relevant dynamic forces such as vibrations and torque fluctuations, thereby reducing false triggers in the integrated design.
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 simple, cost-effective, and integrated squeeze protection that accurately detects collisions in both upward and downward directions, reducing the likelihood of false alarms and ensuring safe operation by filtering out non-relevant dynamic forces, thus enhancing user safety and protecting both objects and the motor drive.
Implementation Method 1
The squeeze protection device comprises a piezo element incorporated in a bracket, which connects the table top to the adjustable part, so that dynamic deviations of the load on the table are reflected in the read-out from the piezo element
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An adjustable table into which a linear actuator (8) is incorporated, where a squeeze protection device (11) is arranged in connection with the table. The device for squeeze protection (11) is arranged in connection with a mounting bracket, which connects the adjustable column (1) to the table top (5). The device for squeeze protection is based on a piezo element (16, 28) incorporated in the mounting bracket (14, 22). The piezo element (16, 28) is equipped with cables (29, 38), so that the signal from the squeeze protection in a simple manner may be communicated to an operating and control device (6), which can stop the motor (10) or momentarily reverse the direction of movement thus releasing a trapped object.