Torque-Limiter Coupling With Shear Retainer for Valve Gearbox Protection
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Solution Overview
Problem
Conventional couplings in valve actuator systems often lead to gearbox damage due to overloading when operators apply excessive torque to unjam stuck valves, resulting in costly repairs and downtime.
Innovation Solution
A torque-limiter coupling with a breakable retainer that disengages from the input shaft when excessive torque is applied, preventing damage to the gearbox by allowing the coupling to rotate independently, thus reducing the need for costly repairs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional couplings are used to transmit torque from handwheel to gearbox, then sufficient torque transmission is achieved, but gearbox damage occurs when excessive torque is applied
Solution Approach 1:
The coupling incorporates a disposable shear pin that is designed to fail at a predetermined torque level. When excessive torque is applied, the shear pin breaks, allowing the coupling to disengage and protect the expensive gearbox from damage. The shear pin is a low-cost component that can be easily replaced, while the gearbox remains intact.
Solution Approach 2:
The coupling design includes a predetermined failure mechanism (shear pin) that activates before the gearbox can be damaged. This pre-planned weak point absorbs the excessive torque through controlled failure, cushioning the gearbox from the harmful effects of operator over-torquing during valve unjamming operations.
2Ease of operation
If operators apply excessive torque to unjam stuck valves, then valve unjamming may be achieved, but costly gearbox damage occurs
Solution Approach 1:
The shear pin is designed as a low-cost, easily replaceable component that sacrifices itself to protect the gearbox. When the pin breaks during excessive torque application, operators can quickly replace it without expensive repairs, maintaining ease of operation while preventing costly damage.
Solution Approach 2:
The coupling mechanism extracts the protective function from the gearbox system by introducing a separate, dedicated torque-limiting component (shear pin). This extracted protection mechanism handles the excessive torque independently, preventing it from reaching the gearbox while allowing operators to continue unjamming operations.
3Force
If replaceable pin coupling is used with splined surfaces, then torque transmission is sufficient, but the coupling may jam and require replacement of entire gearbox
Solution Approach 1:
The coupling is segmented into distinct functional components: the coupling body, the shear pin, and the splined surfaces. This segmentation allows the shear pin to fail independently without affecting the entire coupling or gearbox assembly, reducing device complexity consequences when failure occurs.
Solution Approach 2:
The shear pin acts as an intermediary element between the coupling and the gearbox input shaft. It mediates the torque transmission, allowing normal operation while providing a controlled failure mode that protects the gearbox, thereby simplifying the overall system response to overload conditions.
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 torque-limiter coupling effectively prevents gearbox damage by disengaging under high torque, minimizing repair costs and downtime by allowing the system to function without replacing the gearbox or coupling.
Implementation Method 1
a retainer extending between the torque-limiter coupling and the input shaft to transmit torque therebetween
Implementation Method 2
the retainer operable to disengage the torque-limiter coupling from the input shaft in response to a torque applied to the torque limiter-coupling exceeding a critical torque predetermined to prevent damage to the gearbox assembly
Data Source
AI summary
A valve actuator system includes a gearbox assembly including an output gear for coupling to a valve stem, an input gear operably coupled to the output gear to drive rotation of the output gear and an input shaft operably coupled to the input gear to drive rotation of the input gear, a torque-limiter coupling having a solid body defining a proximal end and a distal end, the proximal end including a recessed interior accepting the input shaft of the gearbox assembly, a retainer extending between the torque-limiter coupling and the input shaft to transmit torque therebetween, the retainer operable to disengage the torque-limiter coupling from the input shaft in response to a torque applied to the torque limiter-coupling exceeding a critical torque predetermined to prevent damage to the gearbox assembly, and an actuator operatively coupled to the proximal end of the torque-limiter coupling to provide torque to the torque-limiter coupling.