Nonlinear Spring Clutch for Hand-Held Power Tools
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Solution Overview
Problem
Torque-dependent, releasable clutches in hand-held power tools face limitations in ensuring reliable release over a wide range of torques due to linear spring characteristics, which restrict the minimum and maximum achievable torque, leading to inconsistent operating behavior.
Innovation Solution
Employing a spring element with a nonlinear load-displacement characteristic, specifically a progressive load-displacement characteristic, allows for a wider range of pretensioning force variation, enabling adjustable release torque across a broader torque range without altering the clutch design complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear spring characteristic is used, then the clutch structure is simple, but the torque range is limited and release reliability is reduced
Solution Approach 1:
The patent applies parameter changes by transitioning from a linear spring characteristic to a nonlinear spring characteristic. This changes the physical parameter of the spring's load-displacement relationship, enabling the pretensioning force to increase more rapidly with displacement. This nonlinear parameter change allows the clutch to achieve reliable release across a wider torque range without adding structural complexity
2Force
If the pretensioning force is increased to ensure reliable release, then the minimum torque is improved, but the maximum torque is limited by spring length
Solution Approach 1:
The patent uses parameter changes in the spring characteristic to achieve a progressive load-displacement relationship. This allows the spring to generate higher pretensioning forces within the same length constraints by increasing the rate of force development as the spring compresses, rather than relying solely on increased spring length
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 ensures reliable clutch release over a wide torque range with adjustable sensitivity across the entire torque range, enhancing operating reliability and preventing premature clutch opening due to zero pretension force.
Implementation Method 1
a spring element (40), which pretensions the second clutch element (32) in the direction of the first clutch element (30)
Implementation Method 2
When the torque reaches a certain value, the ball begins to ascend on the cam element, due to the circumferential force acting thereupon
Data Source
AI summary
A torque-dependent, releasable clutch for a hand-held power tool is specified, which includes a first clutch element, which interacts with a second clutch element to transmit a torque, at least one of the two clutch elements being movable with respect to the other clutch element and being pretensioned by a spring element, the spring element having a nonlinear load-displacement characteristic.