DTH Hammer Bit Spline Geometry for Automatic Alignment
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Solution Overview
Problem
The manual alignment of splines between a drill bit and a driver sub in DTH percussive hammer drilling is inefficient and lacks automation, requiring a more reliable and simplified assembly method.
Innovation Solution
A drill bit and driver sub design with non-perpendicular rearward axially outer edges on bit spline tips and optional alignment pins, allowing for automated spline alignment through translational movement without the need for sensors or actuators, reducing deformation and rotational movement during insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If manual alignment method is used, then alignment can be achieved, but automation is not possible and efficiency is low
Solution Approach 1:
The spline tip geometry is designed to automatically guide alignment during axial insertion. The non-perpendicular rearward edge creates self-aligning contact surfaces that enable the bit to automatically orient itself with the driver sub splines through pure translational movement, eliminating the need for manual rotational alignment or complex automated positioning systems
Solution Approach 2:
The alignment pin protrudes from the driver sub spline tip before insertion, creating a preliminary contact point that guides the bit spline tip into correct alignment. This preliminary geometric constraint ensures proper orientation is established before full engagement, enabling automated alignment through simple axial movement
2Ease of operation
If traditional perpendicular spline edges are used, then manufacturing is simple, but alignment requires rotational movement and sensors
Solution Approach 1:
The spline tip geometry features an asymmetric non-perpendicular rearward edge that creates a unique contact surface angle. This asymmetric geometry ensures that only one rotational position allows proper engagement between bit and driver sub splines, providing inherent alignment guidance without requiring sensors or complex positioning systems
Solution Approach 2:
The invention transforms the alignment problem from a two-dimensional rotational adjustment problem into a one-dimensional axial insertion problem. By designing the spline tip edge at a non-perpendicular angle to the longitudinal axis, the alignment function is achieved through axial translational movement alone, eliminating the need for rotational actuators or sensors
3Ease of manufacture
If standard spline geometry is used, then manufacturing is conventional, but friction and deformation occur during insertion
Solution Approach 1:
The non-perpendicular rearward edge geometry creates a tapered contact surface that facilitates gradual engagement during insertion. This geometric modification reduces sudden impact and friction forces by distributing contact over a progressive engagement sequence, minimizing deformation while remaining compatible with standard manufacturing processes
Data Source
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AI summary
A hammer drill assembly (2) for coupling to a drill string having a drill bit (12) positioned at the forward end (8) having a drill head (16) and a bit shaft (14); wherein a plurality of axially extending bit splines (28) project radially outwards from a radially outward facing surface of the bit shaft; wherein each of the bit splines comprises a bit spline tip (30) at its axially rearward end having a rearward axially outer edge (48) and a central bit spline longitudinal axis (32); and a driver sub (26) provided axially rearward of the drill bit comprising a plurality of axially extending driver sub splines (34) projecting radially inwards from an inward facing surface of the driver sub; characterised in that: the rearward axially outer edge on at least of one of bit spline tips is non-perpendicular to the bit spline longitudinal axis along at least 25% of the width of the bit spline tip.