Towed Cable Safety System with Over-Damped Sheave
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Solution Overview
Problem
Existing variable depth sonar systems face impracticality for fleet use due to large handling systems, and current safety measures to prevent cable tension surges often result in the loss of the towed cable system.
Innovation Solution
A towed array safety system that includes a tension meter to detect surges, a software tool to estimate and apply necessary torque, and a high-powered motor to manage rotational inertia, combined with an over-damped sheave mechanism to increase response time and prevent cable loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a handling system with rated load higher than cable breaking strength is used, then cable tension surge safety is improved, but the cable breaks first leading to loss of towed cable system
Solution Approach 1:
The patent replaces the mechanical safety mechanism (designing cable to break first) with an automated control system. A tension meter detects tension surges, and a processor controls a motor to apply torque to the winch, preventing cable breakage through active control rather than passive mechanical design.
Solution Approach 2:
The system implements feedback control by continuously monitoring cable tension through a tension meter and adjusting motor torque output based on real-time tension readings. The processor receives tension data, compares it to thresholds, and modulates motor torque accordingly to prevent tension surges from causing cable failure.
2Quantity of substance
If a large amount of tow cable is stored on the winch, then cable availability is improved, but rotational inertia increases making it harder to unreel quickly
Solution Approach 1:
The system performs preliminary computation of the torque constant K using pre-stored cable characteristics and winch parameters. The processor calculates the required torque in advance based on the estimated amount of cable on the winch, allowing the motor to apply the correct torque magnitude before the unreeling process begins, thus overcoming rotational inertia effectively.
Solution Approach 2:
The patent replaces purely mechanical cable handling with an automated electro-mechanical system. The motor controlled by the processor substitutes for manual or passive mechanical unreeling, providing precise torque control to overcome the rotational inertia created by large amounts of cable on the winch.
3Speed
If the winch speeds up quickly to relieve tension surge, then response time is improved, but cable loss increases due to lack of control
Solution Approach 1:
The system uses feedback control to manage winch speed and torque dynamically. The tension meter provides continuous feedback on cable tension, and the processor adjusts motor torque and winch speed accordingly. This prevents uncontrolled rapid unreeling while still enabling quick response to tension surges, maintaining cable control throughout the process.
Solution Approach 2:
The system implements dynamic control of the winch operation. The motor torque and winch speed are not fixed but are continuously adjusted based on real-time tension readings and the unreeling process state. This dynamic adjustment allows the system to respond quickly to tension surges while preventing cable loss through controlled, adaptive operation.
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 system effectively prevents cable loss during tension surges by accurately managing torque and inertia, providing enhanced safety without requiring higher-rated load cables, thus avoiding catastrophic failures.
Implementation Method 1
a tension meter that detects a measured tension exceeding a preset threshold
Implementation Method 2
a high-powered motor automatically starts with a torque and speed based on a estimate of the torque required
Implementation Method 3
The motor supplies an initial torque required to overcome rotational inertia during the unreeling of the tow cable
Implementation Method 4
The system is mechanically over-damped to increase a time constant of a transient tension surge
Data Source
AI summary
A safety system and method of use is provided for a tow cable handling system. In use, the cable is from a winch and onto a sheave where a cable tension surge is transmitted to a meter and onto a software element. The software of a controller determines torque needed from a motor to increase winch speed to unreel cable to relieve the surge but not too much that the cable will unreel off the winch. Once the surge concludes, the motor reverses and decreases speed of the winch. If the tension surge is transient, then the motor can increase the winch speed and then slow down the winch before the cable completely unreels. The sheave is suspended by a spring and a dashpot for an over-damped response to increase the time for the winch to speed up to an acceptable speed.