Hydraulic Tensioning Device for Parallel Threaded Rods
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Solution Overview
Problem
Existing methods for tensioning threaded rods, such as applying tightening torque, suffer from variable frictional forces leading to unpredictable axial prestressing and residual torsional stresses, which can cause surface deterioration and lack precision and homogeneity in tightening, making it difficult to achieve secure and efficient assembly.
Innovation Solution
A device with a plurality of hydraulic actuators and crowns that apply axial tension to multiple threaded rods simultaneously, using a system of hydraulic chambers, pistons, and tie rods to ensure uniform and precise tensioning, while reducing the number of elements and allowing for efficient assembly of large-diameter components like boiler covers and bearing rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tightening torque is applied to tension threaded rods, then the rods can be secured, but friction causes variable and unpredictable axial prestressing force
Solution Approach 1:
The patent replaces the torque-based mechanical tightening system with a direct axial tensioning system using hydraulic actuators. Instead of applying rotational torque that converts to axial force through friction-dependent thread engagement, the invention applies axial tension directly along the rod axis, eliminating the friction variable and providing precise, predictable prestressing force.
Solution Approach 2:
The patent employs hydraulic actuators to generate and apply axial tensioning forces. The hydraulic system provides controlled, measurable, and adjustable axial forces directly to the threaded rods, replacing the indirect and friction-dependent torque application method with a direct hydraulic force application that enables precise control over the axial prestressing force.
2Reliability
If tightening torque is applied to tension threaded rods, then the rods can be secured, but residual torsional stresses remain in the rod
Solution Approach 1:
The patent eliminates the torsional stress issue by replacing the rotational torque application mechanism with a direct axial tensioning mechanism. By applying force directly along the rod axis through hydraulic actuators rather than through rotational torque, the system achieves secure rod fixation without introducing harmful residual torsional stresses that would compromise rod integrity.
3Reliability
If tightening torque is applied to tension threaded rods, then the rods can be secured, but surface deterioration occurs at threads and contact faces
Solution Approach 1:
The patent prevents surface deterioration by substituting the high-friction torque-based thread engagement system with a direct axial tensioning system. By eliminating the rotational torque that generates significant frictional forces at threads and contact faces, the invention secures rods reliably without causing wear, galling, or surface damage to critical contact surfaces.
4Strength
If threaded rods are brought closer together to increase rigidity, then assembly rigidity increases, but simultaneous tensioning becomes more difficult
Solution Approach 1:
The patent employs a universal tensioning system where multiple hydraulic actuators share common hydraulic supply and control lines, allowing simultaneous tensioning of multiple closely-spaced rods through a single integrated system. This multi-functional approach enables one hydraulic system to service multiple rods, reducing overall device complexity despite the increased number of rods being tensioned simultaneously.
Solution Approach 2:
The patent merges multiple individual tensioning operations into a single simultaneous operation by integrating multiple hydraulic actuators into a unified system with common hydraulic lines and control mechanisms. This merging allows all rods to be tensioned at once, simplifying the overall tensioning process and reducing the complexity that would otherwise arise from managing multiple separate tensioning operations.
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 solution enables precise, uniform, and rapid tensioning of multiple rods, reducing assembly time and material usage, enhancing the security and reliability of bolted assemblies, and allowing for closer rod placement, which increases rigidity and reduces external dimensions, thus offering significant economic and design benefits.
Implementation Method 1
A plurality of lower hydraulic chambers are formed in the lower crown and a plurality of upper hydraulic chambers are formed in the upper crown. An annular actuator piston is disposed in each hydraulic chamber.
Data Source
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AI summary
Device (1) for tensioning parallel threaded rods, comprising a plurality of actuators (4, 5) able to exert a tensile axial force, each actuator (4, 5) being associated with a tie rod (19) that transmits the tensile axial force to one end of one of the threaded rods, a lower crown (3) and an upper crown (2) which are coaxial, a plurality of lower hydraulic chambers being formed in the lower crown (3) and a plurality of upper hydraulic chambers being formed in the upper crown (2), an annular actuator piston (14) being positioned in each hydraulic chamber (15), the distance between the axes of two adjacent pistons (14), one positioned in a lower hydraulic chamber and the other positioned in an upper hydraulic chamber being smaller than the diameter of said pistons (14).