Piezoelectric Braking Unit for Fast Screwdriver Test Benches

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Solution Overview

Problem

Current hydraulic braking systems in test benches for industrial screwdrivers are limited by their slow frequency response, restricting the maximum rotation speed that can be tested due to their bandwidth, which typically settles below 100 Hz, making it difficult to simulate faster tightening strategies.

Innovation Solution

The implementation of piezoelectric actuators with a much faster frequency response (around 10 KHz) replaces traditional hydraulic brakes, utilizing the inverse piezoelectric effect to convert electrical energy into mechanical forces and movements for precise braking control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If hydraulic brakes are used in the test bench, then large amounts of energy can be transferred, but the frequency response is slow (bandwidth below 100 Hz)

Engineering Contradiction:

Improveenergy transfer capabilityVSAvoidfrequency response

Core Design Contradiction:

PowerVSSpeed

Solution Approach 1:

The patent replaces the hydraulic actuation system with a piezoelectric actuation system. The piezoelectric elements convert electrical energy directly into mechanical displacement, eliminating the hydraulic fluid medium and associated bandwidth limitations. This substitution enables the braking device to achieve a frequency response in the order of 10 KHz while maintaining the ability to transfer large amounts of energy for braking the screwdriver rotor.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Force

If hydraulic actuation system is used, then braking force can be generated, but the minimum braking duration time is limited due to bandwidth restrictions

Engineering Contradiction:

Improvebraking forceVSAvoidminimum braking duration time

Core Design Contradiction:

ForceVSDuration of action of moving object

Solution Approach 1:

The patent substitutes the hydraulic actuation system with piezoelectric elements that directly convert electrical signals into mechanical braking force. This eliminates the slow response inherent in hydraulic systems, allowing the braking device to achieve very short minimum braking duration times corresponding to frequency responses in the order of 10 KHz, while maintaining sufficient braking force to stop the screwdriver rotor effectively.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If hydraulic brakes with common pressure regulating valve are used, then system complexity is reduced, but the maximum rotation speed that can be tested is limited

Engineering Contradiction:

Improvesystem complexityVSAvoidmaximum rotation speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The patent replaces the hydraulic brake system with a piezoelectric-based braking device that uses electronic control instead of hydraulic pressure regulation. The piezoelectric elements are driven by electronic signals from the control unit, eliminating the need for pressure regulating valves and hydraulic distributors. This electronic actuation system achieves bandwidths in the order of 10 KHz, enabling the test bench to accurately test screwdrivers rotating at much higher speeds while actually reducing overall system complexity through the elimination of hydraulic components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables higher precision and faster braking capabilities, allowing for the testing of screwdrivers at higher rotation speeds by overcoming the bandwidth limitations of hydraulic systems, thereby improving the testing capacity of industrial screwdrivers.

Implementation Method 1

The movement of said actuator is provided by at least one piezoelectric element (19). Piezoelectric motors exploit the inverse piezoelectric effect by converting electrical energy (voltage and current) into mechanical energy (forces and movements).

Methodology Applied

Scientific EffectInverse piezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11879797B2Braking device positionable on test benches of correct operation of industrial screwdrivers

Publication Date: 2024.01.23 ATLAS COPCO IND TECHNIQUE AB INTELLECTUAL PROPERTY DEPARTMENT

AI summary

Braking device inserted in a test bench (2) for checking the correct operation of industrial screwdrivers, wherein the braking simulates a tightening operation of such screwdriver, comprising a container body (1) on the top of which a coupling (11) protrudes, suitable for coupling with the head (3) of the screwdriver to be tested, said coupling (11) being connected, by means of a shaft (12), to a braking unit (13), an electronic torque and angle detector (14) of the shaft rotation (12). Such braking unit (13) comprises a plate (14), rotated by the screwdriver, which is braked by suitable friction surfaces (15) moved towards the plate by the movement of an actuator; the movement of such actuator is performed by means of at least one electronically controlled piezoelectric element (17).