Cable Stretching Machine Safety Plant with Negative Brake and Hydraulic Accumulator
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Solution Overview
Problem
Existing cable stretching machines face dangerous conditions and overload situations due to breakdowns in electrical or hydraulic components, leading to loss of tension and potential damage or instability, especially when using helicopters for stretching.
Innovation Solution
A safety device with a negative brake and hydraulic accumulator that can selectively activate and deactivate to maintain capstan rotation, combined with a motorized drive for the maximum pressure valve to regulate working pressure, ensuring controlled tension and preventing recoils during breakdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a maximum pressure valve with proportional electrical command is used to regulate working pressure, then the tension in the stretching cable can be precisely controlled, but the system becomes vulnerable to electrical drive failures that cause complete valve opening and loss of tension
Solution Approach 1:
A distributor valve is introduced as an intermediary component between the electrical command system and the maximum pressure valve. This distributor valve, when failed, directs hydraulic fluid to activate the negative brake rather than completely opening the maximum pressure valve, thereby maintaining system reliability while preserving tension control precision through the backup braking mechanism.
Solution Approach 2:
The negative brake is pre-configured as a safety mechanism that can be activated beforehand through the distributor valve in case of electrical failure. This prior cushioning ensures that when electrical drive fails, the system immediately engages the mechanical brake to prevent complete loss of tension, cushioning the impact of the failure before it can cause dangerous conditions.
2Reliability
If a negative brake with automatic drive is used to hold the conductor under tension during stops, then safety is improved, but the system becomes vulnerable to distributor valve failures that cause sudden brake activation and cable recoil
Solution Approach 1:
The system incorporates feedback through the distributor valve that monitors the state of the negative brake and hydraulic pressure. When the brake is activated, the distributor valve receives feedback signals that prevent premature or simultaneous activation of both brakes, thereby eliminating the harmful feedback loop that causes cable recoil and overload while maintaining safety during stops.
Solution Approach 2:
The distributor valve dynamically controls the activation sequence of the negative brake and maximum pressure valve based on real-time system conditions. This dynamic control ensures that brakes are activated in a coordinated manner rather than simultaneously, adapting to operational needs and preventing harmful recoil while maintaining safety during machine stops and transitions.
3Reliability
If both negative brake and maximum pressure valve are activated simultaneously during electrical failure, then tension is maintained, but dangerous overload conditions occur on the cable and drawing means
Solution Approach 1:
The braking function is segmented into two distinct mechanisms: the negative brake for holding tension during stops and the maximum pressure valve for regulating working pressure during operation. The distributor valve segments the hydraulic fluid flow to activate only the appropriate brake based on system state, preventing simultaneous activation and the dangerous overload forces that result from both brakes engaging at once while maintaining reliable tension control.
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 prevents loss of tension and recoils, maintaining stable operation and safety during electrical or hydraulic failures, ensuring the cable stretching process can continue without overload or instability.
Implementation Method 1
means to accumulate pressure energy of the working fluid, such as for example a hydraulic accumulator
Implementation Method 2
a pumping device connected to the negative brake and configured to de-activate the latter during the normal use of the stretching machine, putting a working fluid under pressure
Data Source
AI summary
Safety plant for a stretching machine (1 1) of the brake type comprising a negative brake (22) which can be selectively activated and de-activated so as to constrain and respectively allow the rotation of at least one capstan (12) which supports cables, a pumping device (24) connected to the negative brake (22) and configured to de-activate the latter during the normal use of the stretching machine (11), putting a working fluid under pressure, pressure energy accumulation means (32) of said working fluid, and a maximum pressure valve (18) configured to regulate the working pressure of a hydraulic motor (13) for controlling the twisting torque applied to the capstan (12). The plant also comprises a motorized drive device (19) connected to the maximum pressure valve (18) and provided to selectively regulate the action of the latter on the hydraulic motor (13), even in a breakdown condition of at least the pumping device (24), in order to maintain the working pressure of the hydraulic motor (13) and to maintain the negative brake (22) de-activated by the intervention of the pressure energy accumulation means (32).