Drill Head Adapter Tapering Wedge Surfaces
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Solution Overview
Problem
Existing drilling tools face challenges in maintaining a durable threaded connection between the drill head and adapter during percussion or rotary percussion drilling, leading to material deformations and difficulties in loosening and retrieving the drill pipe or adapter after drilling, resulting in potential loss and excessive wear.
Innovation Solution
The design features complementary wedge surfaces with a smaller pitch angle than the internal and external threads, along with thread roots extending beyond thread heads, to absorb impact and torque stresses, reducing axial loads on threads and ensuring secure detachment after drilling, while hardened wedge surfaces prevent wear and reuse of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a threaded connection is used between drill head and adapter, then the connection can be secured during drilling, but the thread is subjected to excessive impact stress and torque leading to material deformation and wear
Solution Approach 1:
The connection interface is segmented into two distinct functional zones: wedge surfaces for absorbing impact stresses and end faces for absorbing torque stresses. This segmentation allows each surface to specialize in handling specific types of loads, preventing the thread from being subjected to combined excessive stresses that lead to deformation and wear.
Solution Approach 2:
The solution introduces a new geometric dimension by creating inclined wedge surfaces at a specific angle (5°-15°) relative to the axial direction. This angular dimension allows the wedge surfaces to convert axial impact forces into radial and tangential components, effectively distributing the impact stress away from the thread connection.
2Reliability
If the pitch angle of wedge surfaces is smaller than the thread pitch angle, then the thread is relieved from axial impact stress, but the wedge surfaces must bear the full impact load
Solution Approach 1:
The wedge surfaces are given specific local properties through hardening treatment to enhance their load-bearing capacity. This local quality enhancement allows the wedge surfaces to reliably absorb impact stresses without deforming, while the thread connection remains protected from excessive axial loads.
3Reliability
If complementary wedge surfaces with front teeth are provided, then impact stress is absorbed by wedge surfaces and torque by end faces, but the device complexity increases
Solution Approach 1:
Multiple functions are merged into a single integrated connection interface: the wedge surfaces simultaneously provide impact absorption, centering, and mechanical interlocking through front teeth. The end faces similarly combine torque absorption with positioning functions. This merging avoids the need for separate components for each function, thereby limiting the increase in overall device complexity.
4Reliability
If the thread roots extend beyond the thread heads in the axial direction, then the thread heads are kept free of axial load, but the manufacturing precision requirements increase
Solution Approach 1:
The thread roots are designed to extend beyond the thread heads in advance, creating a geometric configuration that passively protects the thread heads from axial loads during drilling operations. This preliminary geometric arrangement ensures that impact forces are directed to the wedge surfaces before they can reach the thread heads, eliminating the need for active control mechanisms.
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
This design ensures a durable and reusable threaded connection that minimizes material deformation, facilitates safe loosening of the drill rod and adapter, and prevents excessive wear, allowing for reliable detachment and reuse of drilling components.
Implementation Method 1
the wedge surfaces essentially absorbing the impact stress
Implementation Method 2
the wedge surfaces essentially absorbing the impact stress and the end faces absorb the torques
Implementation Method 3
hardened wedge surfaces prevent wear and reuse of components
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
In a two-part drilling tool for the percussive or rotary percussive drilling of holes in soil material or rock material, comprising a drill head (1) and an adapter part (7), which is fixed in an interior of the drill head (1) by way of interacting, complementary threads (11, 14) and is intended for providing the coupling to a drill string, wherein an end face (3) of the drill head (1) that is remote from a borehole interior rests on a complementarily formed stop surface or supporting surface of the adapter part (7), the end face (3) of the drill head (1) that is remote from the borehole interior and the stop surface or supporting surface of the adapter part (7) that interacts with said end face have complementarily formed tapering surfaces (4, 6) with end teeth (5, 8) and a lead angle (α1) of the tapering surfaces (4, 6) smaller than a lead angle (α2) of an internal thread of the drill head (1) or of an external thread interacting therewith of the adapter part (7) or of the drill string.