Hydraulic Power Wrench Torque Control via Piston Stroke Termination
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Solution Overview
Problem
Existing hydraulic power wrench systems face challenges in accurately detecting and ensuring that the desired torque is applied to a rotatable part without additional sensors, as pressure gradients can be influenced by system components and environmental factors, leading to unreliable control and mechanical stress on the piston-cylinder drive.
Innovation Solution
The method involves terminating the loading stroke before the piston abuts the end stop and initiating a return stroke, ensuring that the pressure is transmitted as torque to the rotatable part, allowing for reliable control without additional sensors by determining the piston's end position through its travel path or volume of hydraulic fluid, and using a ratchet for force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the loading stroke is terminated before the piston abuts the end stop, then the torque transmission to the rotatable part is ensured and control reliability is improved, but the mechanical stress on the piston-cylinder drive is reduced
Solution Approach 1:
The control device terminates the loading stroke before the piston reaches the end stop position, preventing the piston from abutting against the end stop. This preliminary termination action ensures that pressure is transmitted to the rotatable part through the ratchet mechanism rather than being absorbed by end-stop impact, thereby ensuring reliable torque transmission and reducing mechanical stress on the piston-cylinder drive.
2Measurement precision
If additional torque sensors are provided to accurately detect torque, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The ratchet mechanism serves as an intermediary element that enables indirect torque measurement. By monitoring the hydraulic pressure required to drive the piston through the ratchet mechanism during the loading stroke, the control device can determine the torque applied to the rotatable part without requiring direct torque sensors. This intermediary approach maintains measurement precision while avoiding additional sensors on the power wrench itself.
Solution Approach 2:
The patent replaces direct mechanical torque sensing with a hydraulic pressure-based measurement system. The control device measures hydraulic pressure and uses it to infer torque values, substituting complex mechanical torque sensors with simpler pressure sensors and computational methods. This substitution reduces device complexity while maintaining the ability to accurately detect and control torque.
3Power
If the piston-cylinder drive operates with high pressure to achieve desired torque, then power output is improved, but mechanical stress on the drive increases
Solution Approach 1:
The control device terminates the loading stroke before the piston reaches the end stop, preventing impact loads that would otherwise occur. This allows the system to operate at high pressures for extended periods to achieve desired torque levels without subjecting the piston-cylinder drive to sudden stress spikes from end-stop abutment, thereby maintaining power output while reducing mechanical stress.
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
This approach guarantees that the desired torque is applied to the rotatable part, reduces mechanical stress on the piston-cylinder drive, and enhances control reliability by avoiding end stop issues, allowing for simplified and sensor-independent operation.
Implementation Method 1
a hydraulic piston-cylinder drive operated by a hydraulic pressure source
Implementation Method 2
a ratchet, wherein a torque is applied to the rotatable part during a loading stroke
Data Source
AI summary
A method for rotating a rotatable part using a hydraulic piston-cylinder drive operated by a hydraulic pressure source and having at least one piston and a ratchet, wherein a torque is applied to the rotatable part during a loading stroke and the piston is moved into a starting position via a return stroke. The loading stroke ends when an end position of the piston is reached and subsequently the return stroke is started, wherein the end position is a position of the piston before the piston abuts against an end stop.