Percussion Drilling Head Auxiliary Bit Geometry
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Solution Overview
Problem
Existing percussion drilling tools for stone materials face challenges in maintaining uniform drilling capacity and reducing sliding friction over time, particularly with sharp bits, leading to premature damage and inefficiency.
Innovation Solution
A solid hard material head with circumferentially offset auxiliary bits featuring a circular arc section and a straight outer section, inclined radially outward, which reduces friction and optimizes cutting performance by allowing drillings to be removed radially and transported inwardly, with specific angle configurations for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary bits have cutting edges extending exactly tangentially, then the drilling head is reliably lifted upon striking reinforcing metal, but the sliding friction is substantially higher in new condition
Solution Approach 1:
The auxiliary cutting edge is designed with non-uniform geometry: a circular arc section at the tip for reliable lifting, and a straight outer section inclined radially outward for reduced friction. This local differentiation allows each portion to perform its specific function optimally without compromising the other.
Solution Approach 2:
The auxiliary cutting edge incorporates a circular arc section that is curved in the direction opposite to the rotational direction. This curvature provides tangential components that enable the auxiliary bit to lift the drilling head reliably when striking reinforcing metal, while the subsequent straight section reduces friction.
2Object-affected harmful factors
If the straight outer section is inclined radially outwardly, then the friction is substantially reduced and drillings are removed radially, but the auxiliary cutting edge must end at a distance from the rotational axis
Solution Approach 1:
The axial recess is positioned ahead of the main bit in the rotational direction, creating a preliminary path for drillings removal. This prevents drillings from accumulating at the auxiliary cutting edge and interfering with the cutting action, thereby maintaining reduced friction throughout operation.
Solution Approach 2:
The auxiliary cutting edge is designed to operate in multiple dimensions: the circular arc section provides tangential lifting action, while the straight outer section inclined radially outward provides radial drillings removal. This multi-dimensional approach resolves the conflict between friction reduction and geometric constraints.
3Object-affected harmful factors
If the circular arc section is curved in direction opposite the rotational direction, then reinforcing metal can slide substantially without friction, but the auxiliary cutting edge requires increased tangential components
Solution Approach 1:
The auxiliary cutting edge is differentiated into distinct sections with specific geometries: the circular arc section provides tangential components for frictionless sliding over reinforcing metal, while the straight outer section provides radial inclination for drillings removal. Each section is optimized for its specific function.
Solution Approach 2:
The circular arc section is curved in the direction opposite to the rotational direction, creating tangential components that allow reinforcing metal to slide over the auxiliary cutting edge with minimal friction. This curvature is essential for the auxiliary bit's function of preventing main bit damage.
Data Source
AI summary
A solid hard material head for a percussion drilling tool rotatable about a rotational axis (A) in a rotational direction (ω), includes at least one main bit and at least one auxiliary bit (5), circumferentially offset relative to the at least one main bit (3) and having an auxiliary cutting edge (6) formed, at least piecewise, as a circular arc section (7) spaced from the rotational axis (A) radially inwardly and inclined in a radial direction, and a straight outer section (8) extending radially outwardly with respect to the circular arc section (7) and inclined in the radial direction.