Electric Actuator Brake Release for Controlled Fail-Safe Return
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Solution Overview
Problem
Safety critical actuators face challenges in achieving reliable fail-safe return movement and managing stored energy transformation, particularly in oil and gas applications where high torque and low friction are required for cutting wire line intervention lines, while minimizing redundancy and maintaining high Safety Integrity Level (SIL) classification.
Innovation Solution
An electric actuator with a speed reducer/gear assembly housing that co-rotates with the rotation to linear transformer, featuring a braking mechanism activated by return speed and force, providing additional energy for cutting wire lines and integrating safety locks and external overrides to prevent internal member rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high ratio gear reducer is used to prevent reverse driving of the brake, then the brake can be held off without power consumption, but the device complexity increases due to the need for an electric clutch and additional control mechanisms
Solution Approach 1:
The patent extracts the clutch mechanism from the system by using a self-locking planetary gear set that inherently prevents reverse driving without requiring an electric clutch. The high ratio gear reducer is designed with asymmetric tooth profiles and locking elements that mechanically block reverse motion, eliminating the need for active clutch control and reducing overall device complexity while maintaining brake holding reliability.
Solution Approach 2:
Instead of using a clutch to allow forward motion and prevent reverse motion, the invention inverts the approach by designing the gear reducer to naturally allow forward motion through controlled slippage while preventing reverse motion through mechanical locking features. The planetary gear set uses one-way bearings and asymmetric tooth engagement to achieve this inverted control logic.
2Ease of operation
If an electric clutch is added to control brake engagement, then the brake can be released during operation, but the device complexity and potential failure points increase
Solution Approach 1:
The patent removes the electric clutch component entirely by implementing a clutchless brake release mechanism. The high ratio gear reducer incorporates a spring-loaded brake that is automatically released when the motor drives the planetary gear set forward, utilizing the motor's own torque to overcome the spring force and disengage the brake without requiring a separate clutch mechanism.
Solution Approach 2:
The brake release mechanism is self-actuating through the motor's driving torque. When the motor operates, it automatically overcomes the spring force and releases the brake through the planetary gear mechanism, eliminating the need for external clutch control systems and reducing complexity while maintaining operational flexibility.
3Reliability
If a spring is used to return the actuator to fail-safe position upon power loss, then the fail-safe function is achieved, but the stored energy must be precisely controlled to avoid damage from excess energy
Solution Approach 1:
The patent implements a dynamic energy dissipation system using a viscous fluid damper that automatically adjusts the braking force based on the return speed of the actuator. The damper's resistance increases with speed, providing strong damping during rapid fail-safe return while allowing controlled movement during normal operation. This dynamic characteristic eliminates the need for complex mechanical energy control mechanisms while ensuring reliable fail-safe function and preventing damage from excess energy.
Solution Approach 2:
The invention uses a viscous fluid damping mechanism to control the spring's stored energy during fail-safe return. The fluid damper creates speed-dependent resistance that dissipates the spring's potential energy as heat, preventing excessive force from damaging the actuator components while ensuring complete return to the fail-safe position. This hydraulic approach simplifies energy control compared to mechanical mechanisms.
4Force
If the speed reducer housing is allowed to co-rotate with the nut, then the holding mechanism load is reduced, but uncontrolled rotation must be managed
Solution Approach 1:
The patent implements a dynamic control system where the speed reducer housing is allowed to co-rotate with the nut during normal operation to reduce holding mechanism load. A viscous fluid damper provides speed-dependent resistance that allows free rotation at low speeds while automatically providing strong damping at high speeds, enabling uncontrolled rotation during normal operation but controlling rotation during fail-safe return to prevent damage.
Solution Approach 2:
The invention changes the resistance parameter of the holding mechanism dynamically through a viscous fluid damper. The damper's resistance force varies with rotational speed, being minimal during normal operation to allow co-rotation and load reduction, but becoming very high during rapid fail-safe return to control and dissipate energy. This parameter change approach simplifies the mechanism compared to complex mechanical locking systems.
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 ensures reliable fail-safe return movement with reduced load on holding mechanisms, self-adapting brake force, and efficient energy dissipation, enhancing Safety Integrity Level compliance and preventing damage to the actuator.
Implementation Method 1
one or more braking mechanisms for controlling a return speed of the electric fail-safe actuator... where the one or more braking mechanisms is activated by a return speed and/or force of the return
Data Source
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AI summary
A release and brake mechanism for an electric actuator comprising a solution to the fail-safe return based on rotational release of the speed reducer/gear assembly housing. In addition, the invention comprises different braking solutions for said rotation to adapt to the different forces and speeds while returning.