Double-Wedge Bolt Pre-Tensioning for Restricted Access Assembly
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Solution Overview
Problem
Existing methods for pre-tensioning bolts are ineffective when access is limited, as they rely on controlling torque, angle of rotation, or torque-to-yield stretch, which are not applicable in situations where bolts are inaccessible, leading to potential deformation or plastic deformation.
Innovation Solution
A control system using a double wedge pre-tensioning element with clamping elements and a tensioning tool that measures and adjusts distances between wedges and washers to achieve proper preloading, allowing for bolt pre-tensioning even in inaccessible locations, preventing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional torque control or angle of rotation methods are used, then pre-tensioning can be achieved in accessible locations, but these methods become ineffective when access to the bolt is limited
Solution Approach 1:
A double wedge mechanism is introduced as an intermediary device between the tensioning tool and the bolt. The wedges convert the axial force from the tensioning tool into radial expansion force that acts on the bolt, enabling pre-tensioning control without requiring direct access to the bolt for traditional torque or angle measurement methods
Solution Approach 2:
The patent replaces traditional mechanical control methods (torque control, angle control) with a displacement control mechanism. A displacement sensor measures the movement of the wedges, and this measurement is used to control the pre-tensioning process, substituting the need for direct bolt access and traditional mechanical measurement methods
2Manufacturing precision
If distance measurement and control is implemented, then pre-tensioning accuracy is improved in inaccessible locations, but device complexity increases
Solution Approach 1:
The double wedge mechanism is designed to be self-measuring through its inherent geometry. The displacement of the wedges directly correlates to the pre-tensioning force applied to the bolt, allowing the system to self-regulate and self-measure without requiring complex external sensing systems or multiple components
Solution Approach 2:
The patent changes the control parameter from torque or angle of rotation to linear displacement of the wedges. This parameter change simplifies the measurement system, as linear displacement can be measured directly and correlated to pre-tensioning force through the known geometry of the wedge mechanism
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
Enables proper pre-tensioning of bolts in restricted access scenarios, preventing deformation and ensuring consistent preloading by measuring and controlling key distances during the pre-tensioning process.
Implementation Method 1
The pre-tensioning element comprises a double wedge consisting of two wedges located about the bolt
Implementation Method 2
reducing the distance between the wedges of the double wedge, increasing the distance between the parts to be joined for pre-tensioning
Implementation Method 3
clamping elements that clamp the wedges of the double wedge once the desired preloading has been achieved
Data Source
AI summary
A method and apparatus for pre-tensioning a bolt that joins two parts, each end of the bolt being threaded into a respective cavity of the two parts. According to one embodiment, the bolt including a double wedge pre-tensioning element, a washer disposed at each side of the double wedge and clamping elements fastening the wedges once the desired preloading has been attained. The bolt is pre-tensioned with a tensioning tool which acts on the pre-tensioning element, reducing a distance between the wedges while increasing the distance between the two parts to be joined and reducing a distance between the outer facing surfaces of the wedges and washers. The control system measures at least one of the distances described, with the tensioning tool acting in accordance with the measured distance.