Wrap Spring Clutch Actuator for Low-Speed Disengagement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wrap spring clutches experience undesirable drag, noise, and wear due to low differences in rotational speed between hubs, making them unsuitable for certain applications, as they struggle to achieve a delicate balance for both engagement and disengagement.
Innovation Solution
A rotational coupling design that includes a wrap spring and a spring actuation member with an actuator to independently unwind the wrap spring, allowing for clutch release regardless of hub rotational speed differences, using a collar and solenoid mechanism to control the unwinding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the interference fit of the wrap spring is increased to improve engagement, then clutch engagement is compromised, but disengagement becomes difficult and causes drag and wear
Solution Approach 1:
The disengagement function is segmented from the engagement function by introducing a separate actuator mechanism. The actuator independently controls spring unwrapping through a ratchet mechanism, separating the forces required for engagement (interference fit) and disengagement (actuator-driven unwrapping), thereby resolving the contradiction between strong engagement and easy disengagement
Solution Approach 2:
The ratchet mechanism acts as an intermediary between the actuator and the wrap spring. It translates the actuator's rotational motion into controlled spring unwrapping while preventing reverse motion, serving as a mechanical mediator that enables disengagement without requiring the spring to overcome its full interference fit force
2Ease of operation
If the interference fit is decreased to facilitate disengagement, then disengagement improves, but clutch engagement becomes insufficient
Solution Approach 1:
The operational functions are segmented into engagement (passive, relying on interference fit) and disengagement (active, driven by actuator). This segmentation allows the interference fit to be optimized for strong engagement while the actuator mechanism provides the necessary force for easy disengagement, eliminating the need to compromise either function
Solution Approach 2:
The actuator performs preliminary action by actively unwrapping the spring before disengagement is needed. By pre-positioning the spring in a controlled unwrapped state through the ratchet mechanism, the system prepares for easy disengagement without requiring reduced interference fit, thereby maintaining both engagement strength and disengagement ease
3Device complexity
If a conventional wrap spring clutch is used in applications with low rotational speed differences, then the clutch structure is simple, but the wrap spring generates noise, vibration, and excessive wear
Solution Approach 1:
The actuator mechanism provides self-service by automatically controlling the spring's wrapped and unwrapped states based on operational needs. It actively manages the spring position to prevent drag and contact during low-speed conditions, thereby eliminating noise and vibration generation without requiring complex external control systems
Solution Approach 2:
The system performs preliminary action by proactively unwrapping the spring when engagement is not required, preventing the spring from contacting the hub during low-speed operation. This anticipatory control eliminates the source of noise, vibration, and wear before they can occur, while adding minimal complexity to the basic clutch structure
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
Facilitates the release of the wrap spring in applications with low rotational speed differences, enabling the use of wrap spring clutches in previously unsuitable applications by minimizing drag and wear, and reducing noise.
Implementation Method 1
A wrap spring is coupled to one of the input and output hubs by an interference fit. When rotation of the hub to which the wrap spring is connected in a first rotational direction causes the spring to tighten down upon the other hub thereby coupling the two hubs together for rotation
Implementation Method 2
an actuator configured to stop rotation of the spring actuation member and the second hub in the first rotational direction
Data Source
AI summary
A rotational coupling is provided. The coupling includes first and second hubs disposed about an axis of rotation. A wrap spring is disposed radially outwardly of the hubs and rotatably couples the hubs upon rotation of the first hub in a first rotational direction. A spring actuation member is configured for rotation about the axis and coupled to one end of the wrap spring. The opposite end of the wrap spring is coupled to the second hub. An actuator is configured to selectively stop rotation of the spring actuation member and the second hub in the first rotational direction and cause rotation of the spring actuation member in a second rotational direction to thereby unwrap the wrap spring. The rotational coupling therefore facilitates disengagement of the wrap spring from the first hub during release of the coupling to prevent undue noise and vibration and reduce wear.