Down the Hole Drilling Piston with Variable Cross-Section
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Solution Overview
Problem
Traditional down-the-hole drilling assemblies face limitations in power output and efficiency due to suboptimal utilization of the available space within the casing bore, leading to reduced drilling performance and increased wear on external components.
Innovation Solution
The design features a piston with maximized working areas within the casing bore, including a central portion and distal portions with specific diameter ratios, and a fluid-powered system with strategically placed passages and chambers to enhance the piston's reciprocating motion, ensuring that the sum of surface areas exposed to pressure equals the casing bore area, thereby increasing percussion frequency and power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the piston working area is increased to maximize power output, then the drilling efficiency and power output are improved, but the stroke length is reduced which limits the percussion frequency
Solution Approach 1:
The invention changes the geometric parameters of the piston, specifically creating a piston with varying cross-sectional diameters (D2, D3, D4) where the central portion has diameter D2 and the distal portions have smaller diameters D3 and D4. This parameter optimization allows the piston to achieve both large working area for high power output and sufficient stroke length for adequate percussion frequency by carefully balancing the diameter ratios within specified ranges (0.3 to 1.0)
Solution Approach 2:
The invention transitions from a traditional piston with uniform cross-section to a piston with variable cross-sectional dimensions along its length. By introducing dimensional variation (different diameters at different positions), the piston achieves both large working area (D2²) and adequate stroke length (L) simultaneously, resolving the contradiction between power output and stroke length
2Productivity
If the stroke length is reduced to increase percussion frequency, then the drilling efficiency is improved, but the power output from the piston is reduced
Solution Approach 1:
The invention optimizes the piston diameter parameters (D2, D3, D4) and their ratios to achieve the desired balance between stroke length and percussion frequency. By setting D3 and D4 within 0.3 to 1.0 times D2, the piston maintains sufficient working area for high power output while allowing reduced stroke length for increased percussion frequency
3Area of moving object
If the available area inside the casing bore is fully utilized, then the working areas of the piston are maximized, but the complexity of the piston structure increases
Solution Approach 1:
The piston is segmented into distinct portions with different functions: a central portion (diameter D2) providing the main working area, and distal portions (diameters D3 and D4) optimized for specific functions. This segmentation allows each portion to be optimized independently while maintaining overall structural integrity and maximizing the total working area within the casing bore
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 enhances the drilling efficiency by reducing the stroke length required to achieve desired striking velocity, resulting in higher frequency and power output while minimizing air volume usage and wear on external components.
Implementation Method 1
a fluid powered piston arranged moveably inside the casing which is capable of shuttling axially back and forth... at least one main feed passage, at least one top feed passage and at least one bottom feed passage arranged to control the feeding of pressurized fluid into the top and bottom working chambers to generate the reciprocating movement of the piston
Implementation Method 2
The fluid acts to both drive the hammer drilling action and to flush chips and fines resultant from the cutting action, rearwardly through the bore hole so as to optimise forward cutting
Implementation Method 3
The piston is configured to strike a drill bit being connected directly to the drilling assembly
Data Source
AI summary
A down the hole drilling assembly having an elongate casing, a fluid powered piston, top and bottom working chambers, a plurality of fluid passages and an exhaust system, wherein the sum of the top work area and a top intermediate work area of the piston is equal to the cross-sectional area of the casing bore.