Medical Cutting Instrument Brazed Joint for Stable Capillary Bonding
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Solution Overview
Problem
Medical cutting instruments with stainless steel or tool steel shank portions and cemented carbide working portions face issues with varying joint strength due to gaps between bonding surfaces during brazing, leading to defective fractions and unstable bonding.
Innovation Solution
A medical cutting instrument with a round stainless steel or tool steel shank portion and a cemented carbide or ceramic working portion, featuring a raised sloped brazing surface with a single apex, allowing point contact and constant gap for stable solder filling, exhibiting capillary phenomenon for enhanced bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction pressure welding or resistance welding is used to bond the shank portion and working portion, then bonding strength is improved, but joint strength variation increases and defect rate increases
Solution Approach 1:
The invention changes the geometric parameters of the brazing surfaces by forming protrusion portions with specific dimensions (height h and diameter d, where 0.05 ≤ h/d ≤ 0.5). This geometric parameter change creates a controlled gap structure that ensures consistent solder flow and bonding, reducing joint strength variation and defect rates while maintaining high bonding strength through the brazing process.
2Ease of manufacture
If flat bonding surfaces are used for brazing, then manufacturing is simplified, but joint strength varies due to gap variations between surfaces
Solution Approach 1:
The invention applies local quality by forming protrusion portions at specific locations on the brazing surfaces. Instead of making the entire surface complex, only localized protrusions are created with specific height and diameter ratios. This localized geometric modification ensures consistent gap control at the bonding interface while keeping the overall manufacturing process simple and the majority of the surface geometry unchanged.
3Strength
If the protrusion portion height is increased to ensure point contact, then joint strength stability is improved, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes the geometric parameters of the protrusion portions by establishing a specific height-to-diameter ratio range (0.05 ≤ h/d ≤ 0.5). This parameter optimization ensures that the protrusions are tall enough to create reliable point contact and consistent gaps for solder flow, yet not so complex that they significantly increase manufacturing difficulty. The standardized ratio provides a balance between performance and manufacturability.
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 stable capillary phenomenon ensures consistent brazing operation and high joint strength, reducing variations and defects, while maintaining ease of processing and cost-effectiveness within a preferred height range of 0.5% to 8% of the brazing surface diameter.
Implementation Method 1
the solder is provided in a space formed between the first brazing surface and the second brazing surface... the stable capillary phenomenon ensures consistent brazing operation
Implementation Method 2
a solder for bonding the first brazing surface and the second brazing surface... are brazed while brazing surfaces are brought into contact
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
A medical cutting instrument which stably exhibits high joint strength obtained by brazing. A cutting instrument (A) is configured by providing a working section (2) to the front end of a shank section (1), the working section (2) consisting of a carbide or a ceramic, the shank section (1) being constructed from a round stainless steel bar or a round tool steel bar. The shank section (1) and the working section (2) are connected through a brazed section (3). The brazed section (3) is the portion at which the shank section (1) and the working section (2) are brazed together while brazing surfaces, which are provided with protrusion sections formed on the shank section (1) and/or the working section (2), are caused to be in contact with each other. The protrusion sections provided on the brazing surfaces each comprise sloped surfaces (5b) having an apex (5a), and the height of the sloped surfaces (5b) is set in the range of 0.5%-8%, inclusive, of the diameter of the brazing surface of the shank section (1).