Percussion Drill Bit Thread Geometry for Longer Rod Life
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Solution Overview
Problem
In single-pass percussion drilling, the thread connection between the drill bit and the drill rod is the weakest link, leading to significant wear and limited service life, with existing designs failing to optimize the service life of both the rod and the bit, and requiring a large variety of drill bits for different drilling conditions.
Innovation Solution
A drill bit with a threaded coupling design where the root bottom is wider than the crest, allowing for compatibility with various rods having different thread crest widths, enabling tailored rod design and extended service life, and reducing the need for multiple drill bit designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thread design with equal root and crest widths is used, then the bit can be connected to standard rods, but the thread connection becomes the weakest link with significant wear and limited service life
Solution Approach 1:
The patent applies asymmetry by designing the thread root width to be greater than the thread crest width. This asymmetric geometry redistributes the stress and wear along the thread interface, preventing the concentration of wear at the crest as in conventional symmetric threads. The wider root provides a larger load-bearing area, enhancing both reliability and service life of the thread connection.
Solution Approach 2:
The patent changes the geometric parameters of the thread profile by specifying that the root width exceeds the crest width. This parameter modification fundamentally alters the stress distribution and wear characteristics of the thread connection, transforming it from a weak link to a durable connection that matches or exceeds the service life of the bit and rod.
2Adaptability or versatility
If multiple drill bit designs are manufactured to accommodate different rod thread crest widths, then compatibility with various rods is achieved, but inventory complexity and manufacturing costs increase
Solution Approach 1:
The patent achieves universality by designing a single drill bit thread profile with asymmetric geometry (wider root than crest) that can accommodate multiple rod thread variations. The asymmetric root design provides a tolerance buffer that allows the same bit to mate with rods having different crest widths, eliminating the need for multiple specialized bit designs and reducing inventory complexity.
Data Source
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Figure 3a~3b
AI summary
An internally threaded bit for percussion drilling is provided, which has thread roots wider than the thread crests. The bit exhibits a reduced rate of ringing off, and can accept drill rods having a range of crest widths.