Threaded Clamping Bushing for High-Force Bore Clamping
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Solution Overview
Problem
Existing clamping devices face issues with unsatisfactory clamping effect due to high radial forces required for form-locking connections and material deformation of workpieces, especially when using spreadable clamping bushings with toothing that penetrate into the workpiece's bore.
Innovation Solution
A clamping bushing with an external thread that engages in an internal thread of the component's bore, creating a form-locking connection, which allows for high clamping forces and greater reliability, and includes a radially expandable design with slitted segments for radial expansion facilitated by a tension rod's conical widening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spreadable clamping bushing with toothing is used to create a form-locking connection, then the clamping reliability is improved, but a large radial force must be exerted on the clamping bushing and the workpiece material must be softer
Solution Approach 1:
The clamping bushing is divided into multiple axial segments separated by radial slits, allowing independent radial expansion of each segment. This segmentation enables the toothing to engage with the workpiece bore wall in a stepwise manner, distributing the radial force requirement across multiple smaller engagement points rather than requiring simultaneous engagement of the entire circumference, thereby reducing the peak radial force needed.
Solution Approach 2:
The invention changes the engagement parameter from requiring the entire clamping bushing to expand simultaneously to allowing sequential or progressive expansion of individual segments. This parameter change in the expansion process reduces the peak radial force requirement while maintaining the form-locking clamping reliability through the toothing engagement.
2Reliability
If a spreadable clamping bushing with toothing is used to create a form-locking connection, then the clamping reliability is improved, but the individual clamping processes lead to a deformation of the workpiece at the inner wall of the bore
Solution Approach 1:
By segmenting the clamping bushing into multiple axial sections with radial slits, the toothing engagement is distributed across multiple smaller contact zones rather than a continuous large-contact zone. This segmentation reduces the localized deformation at any single point on the workpiece inner wall while maintaining overall clamping reliability through the cumulative effect of all segments engaging with the bore.
Solution Approach 2:
The radial slits create local flexibility zones in the clamping bushing, allowing each segment to expand independently and adapt to the local geometry of the workpiece bore. This local quality adjustment enables the toothing to engage with minimal deformation by allowing slight variations in expansion across different axial positions, reducing stress concentration and workpiece deformation.
3Reliability
If the external thread of the clamping bushing has the same thread diameter as the internal thread of the bore in the radially expanded state, then a form-locking thread engagement is achieved, but the clamping bushing cannot be introduced into the blind bore in the radially contracted state
Solution Approach 1:
The clamping bushing transitions dynamically between two radial states: a contracted state for insertion where the external thread diameter is smaller than the internal thread diameter, and an expanded state for clamping where the external thread diameter matches the internal thread diameter. The radial slits enable this dynamic transformation, allowing the bushing to be inserted easily in the contracted state and then expanded in-situ to achieve the form-locking thread engagement.
Solution Approach 2:
The clamping bushing with its contracted external thread fits nested within the larger internal thread bore during insertion, similar to nested dolls. After insertion, the bushing is radially expanded so that the external thread engages with the internal thread walls, transforming from a nested fit to an interference fit that creates the form-locking connection.
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 provides a reliable form-locking connection with high clamping forces, reducing material deformation and enabling secure clamping without excessive radial force, while allowing for easy insertion and expansion of the clamping bushing.
Implementation Method 1
The free end of the tension rod widens conically toward its end and is surrounded by a clamping bushing... due to the conical widening of the free end of the tension rod, to a radial expansion of the clamping bushing
Data Source
AI summary
The invention relates to a clamping bushing (21) for clamping in a bore (3) of a component (2), in particular of a workpiece to be clamped, wherein the clamping bushing (21) is radially contracted in a relaxed state such that the clamping bushing (21) can be inserted into the bore (3) and pulled out of the bore (3), whereas the clamping bushing (21) is radially expanded in a stressed state such that the lateral surface of the clamping bushing (21) forms a mechanical connection to the inner wall of the bore (3). According to the invention, the mechanical connection between the lateral surface of the clamping bushing (21) and the inner wall of the bore (3) is positive-locking and consists of a threaded connection. The invention further relates to a corresponding clamping device (1). An essential feature of the invention is also the possibility of being able to exchange the clamping bolt (tension anchor) by means of a bayonet coupling without having to open hydraulic lines and without removing the clamping element from the device.