Hydraulic Drive Speed Limiting via Dual Flow Paths
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Solution Overview
Problem
Hydraulic drive systems face challenges in safely limiting the speed of piston rods to prevent accidents, especially under external forces like gravity, due to slippage between the motor shaft and actuator, leading to power loss and reduced operational periods.
Innovation Solution
A hydraulic drive system with a connecting line having a first sub-connection with a low flow resistance and a second sub-connection with a higher flow resistance, controlled by stop valves, limits piston rod speed by directing fluid flow through the second sub-connection only in safe mode, reducing power loss and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a baffle is arranged in the discharge and/or feed lines of the hydraulic cylinders to limit the volumetric flow, then the speed of the piston rod is limited to a maximum value, but this results in a loss of power at the baffles which leads to a significant rise in temperature and limits the period of use
Solution Approach 1:
The hydraulic circuit is segmented into two separate cylinder chambers (first cylinder chamber and second cylinder chamber) that are connected via a connecting line. Each chamber can be controlled independently, allowing the system to limit flow to one chamber while maintaining full flow to the other, thereby limiting piston rod speed in one direction without power loss in the other direction.
Solution Approach 2:
The flow limiting feature is applied locally to specific sub-connections rather than globally to the entire hydraulic circuit. The first sub-connection includes a first stop valve for localized flow control, while the second sub-connection includes a baffle with higher flow resistance. This allows speed limitation to be applied only where needed rather than throughout the entire system.
2Speed
If a baffle is designed for maximum supply pressure and unfavorable load situation to limit piston speed, then the piston rod speed is limited, but this represents resistance to piston movement and results in power loss
Solution Approach 1:
The system dynamically switches between different flow paths using stop valves. The first stop valve can be opened or closed depending on operating conditions, allowing the system to adapt between normal mode (with lower flow resistance) and safe mode (with higher flow resistance through the baffle). This dynamic adaptation allows ease of operation under normal conditions while ensuring speed limitation when needed.
3Reliability
If additional baffles are arranged in the discharge and/or feed lines to limit volumetric flow, then the speed of the actuator is limited, but these baffles represent resistance to piston movement and result in power loss
Solution Approach 1:
The hydraulic circuit is divided into two separate cylinder chambers connected via a connecting line with parallel sub-connections. This segmentation allows the system to limit flow through one path (second sub-connection with baffle) while maintaining unrestricted flow through the other path (first sub-connection), thereby achieving reliable speed limitation without continuous power loss.
Solution Approach 2:
The connecting line serves multiple functions: it connects the two cylinder chambers, provides parallel flow paths for flexibility, and incorporates both a stop valve and a baffle to enable both normal operation and speed-limited safe mode. This multi-functionality allows the same component to serve different purposes under different operating 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 system achieves safe, efficient, and economical operation by minimizing power loss and preventing excessive piston rod speed, even under external forces, without requiring complex speed monitoring components, thus enhancing safety and reducing energy consumption.
Implementation Method 1
the second sub-connection has a second flow resistance due to the baffle arranged therein, which is greater than the first flow resistance for the fluid
Implementation Method 2
a hydraulic drive for conveying the fluid from one cylinder chamber into the other cylinder chamber via the connecting line
Data Source
AI summary
A safe hydraulic drive system and process, comprising at least one first cylinder chamber and a second, separate cylinder chamber which are connected to one another via a connecting line to form a fluid-filled hydraulic circuit, and a hydraulic drive for conveying the fluid from one cylinder chamber, via the connecting line, into the other cylinder chamber in which the connecting line is arranged. The connecting line has at least one parallel system, between the hydraulic drive and one of the two cylinder chambers, including at least one first sub-connection with at least one first stop valve and a second sub-connection with a baffle arranged therein. The connecting line, excluding the second sub-connection, has a first flow resistance and the second sub-connection has a second flow resistance due to the baffle arranged therein, which is greater than the first flow resistance for the fluid, wherein the drive system is provided with at least one open first stop valve in normal mode and with a closed first stop valve in safe mode for conveying the fluid, and a suitably high second flow resistance has been selected so that a maximum permissible speed for a piston rod is not exceeded in safe mode, even when an external force acts on the drive system in the direction of movement of the piston rod.