Asymmetric Percussive Drill Bit Gauge Insert Design
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Solution Overview
Problem
In percussive drilling, the wear down of carbide inserts leads to anti-taper, reducing drilling rate and bit lifetime due to lack of space for cuttings removal, and increasing the risk of insert breakage when trying to delay this by increasing protrusion height.
Innovation Solution
Asymmetrically shaped cemented carbide inserts with a greater volume on the radially external side, maintaining drilling speed and delaying anti-taper without increasing the risk of breakage, achieved through specific geometric and material compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the protrusion height of the insert is increased to delay anti-taper, then the lifetime of the drill bit is improved, but the likelihood of insert breakage increases
Solution Approach 1:
The gauge insert employs an asymmetric geometry where the radially external side (facing the bore hole wall) has a greater volume of material than the radially internal side. This asymmetric distribution of material allows the insert to extend further radially outward, increasing the distance between the steel bit body and the bore hole wall without proportionally increasing the bending moment on the insert, thereby delaying anti-taper while managing breakage risk
Solution Approach 2:
The insert design concentrates additional material volume specifically on the radially external side where it is most needed to maintain distance from the bore hole wall. This localized material distribution optimizes the delay of anti-taper occurrence without uniformly increasing the insert's overall size and associated breakage risks
2Length of stationary object
If the protrusion height of the insert is increased to delay anti-taper, then the distance between steel bit body and bore hole wall is increased, but the bending motion of the insert increases leading to premature fracture
Solution Approach 1:
By making the radially external side of the insert longer than the radially internal side, the design efficiently uses material placement to maximize the distance benefit while minimizing the lever arm that causes bending. The asymmetric shape ensures that the additional length is positioned where it provides maximum benefit for delaying anti-taper
3Ease of manufacture
If conventional symmetric inserts are used, then the manufacturing is simpler, but the space for cuttings removal is reduced leading to decreased drilling rate
Solution Approach 1:
The asymmetric geometry of the gauge insert with greater volume on the radially external side creates additional space in the bore hole for cuttings to be removed. This asymmetric design maintains manufacturing feasibility while significantly improving the drilling rate by preventing cuttings accumulation
Data Source
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AI summary
A percussive drill bit for drilling a bore hole comprising a bit body having a front face surrounded by a gauge and a longitudinal bit central axis; and a plurality of gauge inserts embedded in the gauge; wherein the gauge inserts have a longitudinal insert central axis, a cylindrical shank portion; a working tip portion; an radially internal side located on the side nearest to the bit central axis and an radially external side on the side further from the bit central axis; characterized in that: the working tip portion of the gauge inserts have an asymmetric geometry wherein the volume of material on the radially external side is greater than the volume of material on the radially internal side.