Rotating Needle Cage Cold Expansion Tool
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Solution Overview
Problem
Current cold expansion methods using split rings often leave untreated internal surface areas and result in poor residual stress distribution, imposing material and fiber direction restrictions.
Innovation Solution
A tool comprising a cylindrical needle cage driven in rotation by a first drive module, with a rod inserted to radially move needles and a burnisher passing through the cage, ensuring comprehensive surface hardening and improved stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a split ring is used for cold expansion, then the expansion process can be performed, but portions of the internal bore surface remain untreated at the slot area, resulting in poor residual stress distribution
Solution Approach 1:
The expansion tool is segmented into multiple independent needles arranged in a cage structure, allowing each needle to independently work on different portions of the bore surface. This segmentation eliminates the untreated slot area problem inherent in single-piece split ring designs, ensuring complete coverage of the internal surface.
Solution Approach 2:
The needle cage is designed to rotate during the expansion process, dynamically distributing the needles around the bore circumference. This rotational movement ensures that all portions of the bore surface receive uniform treatment, eliminating stationary untreated areas and achieving homogeneous residual stress distribution.
2Ease of manufacture
If a split ring is used for cold expansion, then the process can be completed, but numerous restrictions are imposed due to material and grain direction of the part
Solution Approach 1:
The needle cage expansion tool is designed with universal applicability, capable of effectively treating various materials and grain directions. The multiple needles arranged radially can adapt to different material properties and fiber orientations, eliminating the restrictive conditions imposed by split ring designs and enabling use across diverse workpiece types.
3Strength
If a burnisher is forced through a split ring, then cold expansion is achieved, but the process requires the burnisher outer diameter to be larger than the ring inner diameter, creating geometric constraints
Solution Approach 1:
The needles are nested within a cage structure, with each needle contained in its own radial slot. This nested arrangement allows the needles to be constrained within a compact geometry while still achieving the necessary radial expansion force, eliminating the need for the burnisher diameter to exceed the ring inner diameter.
Solution Approach 2:
The needle cage acts as an intermediary structure between the rod and the bore surface. Instead of directly forcing a large burnisher through a small ring, the rod pushes the needle cage, which then distributes the expansion force through multiple needles, reducing geometric constraints and enabling more flexible tool design.
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 tool effectively hardens the entire internal surface of the bore without untreated areas, enhancing stress distribution and reducing material and fiber direction restrictions.
Implementation Method 1
the needles being configured to move radially away from the first axis of revolution in order to work-harden the bore
Implementation Method 2
the burnisher being configured to radially move the needles of the needle cage when the burnisher passes through the needle cage
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
- Cold expansion tool for a bore through a workpiece. - The expansion tool includes a tool body (4) for manipulating the tool, a drive module (23) for rotating a cylindrical needle cage (5) in the bore (2), the cylindrical needle cage (5) having an axis of revolution (6) around which the needle cage (5) is intended to enter rotation in the bore (2), the needle cage (5) having needles (7) configured to move radially (9) away from the axis of revolution (6) in order to work-harden the bore (2) while the needle cage (5) is driven in rotation by the drive module (23). The expansion tool (1) also includes a rod (11) having a burnisher (14) intended to radially move the needles (7) of the needle cage (5) when the burnisher (14) passes through the needle cage (5) by means of the translation of the rod (11).The rotation of the needle cage (5) allows the entire internal surface of the bore (2) to be work-hardened.