Low-Stress Drill Bit Cavities With Curved Conical Transitions
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Solution Overview
Problem
Existing conical frictional connections in drill bits for percussive drilling lead to high stress concentrations, increasing the risk of fracture and detachment, thereby reducing the drill bit's lifetime and disrupting the connection with the drill rod.
Innovation Solution
A percussive drill bit design featuring a sleeve section with a conical cavity that includes multiple curved connection regions with varying radii, reducing stress concentrations by transitioning smoothly from the conical to the cylindrical region, thereby maintaining a secure connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the conical section of the cavity connects directly to the cylindrical region, then the structure is simple and easy to manufacture, but high stresses are located inside the drill bit which increases the risk of fracture
Solution Approach 1:
The invention introduces a curved connection section with a radius of curvature between 5-120mm between the conical and cylindrical regions. This curved transition replaces the sharp corner connection, distributing stresses more evenly throughout the structure and preventing stress concentration at the junction point, thereby reducing fracture risk while maintaining manufacturing feasibility.
Solution Approach 2:
The invention modifies the geometric parameters of the cavity connection by introducing a controlled radius of curvature (5-120mm) at the transition zone. This parameter change transforms the sharp corner geometry into a smooth curved transition, fundamentally altering the stress distribution pattern without significantly complicating the manufacturing process.
2Device complexity
If the conical section of the cavity connects directly to the cylindrical region, then the structure is simple, but the lifetime of the drill bit is reduced due to increased fracture risk
Solution Approach 1:
The curved connection section with radius of curvature 5-120mm eliminates stress concentration at the conical-cylindrical junction, significantly reducing the risk of fatigue failure and fracture. This extends the operational lifetime of the drill bit while adding only moderate geometric complexity that remains within standard manufacturing capabilities.
Solution Approach 2:
The curved transition section acts as a stress-distributing cushioning element that prevents stress concentration before it can lead to fracture. By designing this curved section in advance with appropriate radius, the patent preemptively protects against the harmful stress concentration that would otherwise occur at a sharp corner connection.
3Device complexity
If the drill bit fractures, then the structure is simple, but the frictional connection is loosened which may result in the drill bit spinning or becoming detached
Solution Approach 1:
The curved connection section prevents drill bit fracture by eliminating stress concentration points, thereby maintaining the integrity of the frictional connection between the drill bit and drill rod. This ensures reliable force transmission and prevents the drill bit from spinning or detaching during operation.
Solution Approach 2:
The curved transition section serves as a preventive measure that cushions against stress concentration before it can cause fracture and subsequent connection failure. By addressing the stress issue beforehand, the patent ensures the frictional connection remains intact and reliable throughout the drill bit's service life.
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 design effectively reduces stress concentrations, minimizing the risk of fracture and detachment, thus extending the drill bit's lifetime and ensuring a stable connection with the drill rod.
Implementation Method 1
the curved connection region reduces the stress in the conical cavity of the drill bit
Data Source
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AI summary
A percussive drill bit comprising a sleeve section and bit section having a longitudinal axis; wherein the sleeve section has an axial end at the opposing end of the drill bit compared to the bit section from which a generally conically shaped internal cavity extends from for receiving a conically shaped drill rod to form a conical frictional connection; wherein the cavity has a conical region nearest to the axial end and a cylindrical region nearest to the bit section; characterised in that: there is connection section joining the conical region to the cylindrical region; the conical region has a straight tapered region with a starting point adjacent to the connection region; wherein the connection section has at a first curved connection section having a first radius, CR1, wherein its tangent,CT1, to a central point along the first curved connection section is positioned at a first distance, CD1, from the taper region starting point.