Percussion Drill Housing Insert With Shrink-Glued Assembly
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Solution Overview
Problem
Existing earth drilling devices, particularly ram drilling devices, face challenges in maintenance and repair due to complex joining processes like friction welding and shrink connections, which require large oversizes and high temperature differences, leading to increased production costs and potential damage to the housing structure.
Innovation Solution
A shrink-glued connection is used to hold an insert in the impact section of the percussion piston, allowing for reduced oversize and temperature differences, enabling easier assembly and disassembly, while maintaining mechanical integrity through the use of a heat-resistant adhesive that hardens in the absence of air, facilitating simpler handling during maintenance and repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If friction welding is used to join the insert in the housing, then the mechanical strength of the connection is improved, but the manufacturing complexity increases due to laborious turning out of the friction weld seam and finish-turning of the housing outer contour
Solution Approach 1:
The patent changes the joining method from friction welding to shrink-fit connection, altering the physical parameters of the joining process. The shrink-fit connection uses thermal expansion and contraction parameters to achieve a secure fit without requiring post-weld machining operations, thus reducing manufacturing complexity while maintaining connection strength
Solution Approach 2:
The shrink-fit connection exploits thermal expansion and contraction of the insert material. The insert is heated to expand its outer diameter, allowing easy insertion into the housing, then cooled to contract and create a tight interference fit, eliminating the need for complex post-weld turning operations
2Ease of manufacture
If shrink connection is used to hold the insert in the housing, then the ease of manufacture is improved by eliminating post-processing, but the device complexity increases due to difficult disassembly and reassembly
Solution Approach 1:
The patent modifies the shrink-fit connection by adding a threaded hole and locking mechanism. The parameter change allows the connection to be easily disassembled by heating the housing again to expand the insert, removing it, and reassembling with a new insert, thus improving ease of repair while maintaining ease of manufacture
Solution Approach 2:
The shrink-fit connection is made dynamic through the addition of a locking mechanism that can be engaged or disengaged. The connection transitions from a permanent static state to a controllable state that can be easily assembled and disassembled on demand, improving both ease of manufacture and ease of repair
3Strength
If large oversize is used for shrink connection to ensure mechanical integrity, then the strength of the connection is improved, but the temperature difference required for joining increases, leading to potential damage to the housing structure
Solution Approach 1:
The patent optimizes the oversize parameter of the shrink-fit connection to a minimal interference fit value. By changing the parameter from large oversize to minimal oversize, the required temperature difference for joining is significantly reduced, preventing thermal damage to the housing structure while maintaining sufficient connection strength through the combination of shrink-fit and locking mechanism
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
The shrink-glued connection reduces production costs, allows for thinner-walled components, and enables the assembly of a complete front drill head housing with reduced stress, enabling easier disassembly and reassembly, while maintaining mechanical energy transfer efficiency.
Implementation Method 1
The insert (4) can be inserted into the housing section (1) by creating a temperature difference between the insert (4) and the housing section (1), as a result of which the inner diameter is temporarily increased
Implementation Method 2
An adhesive which hardens in the absence of air can be used, so that assembly or connection of the insert in the housing can also be made possible
Data Source
Figure 1
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AI summary
The invention relates to a ground drilling device with a percussion piston for drilling into the soil, which comprises at least one housing section for the percussion piston. An insert is arranged in the housing between the end of the drill head and the percussion piston such that the insert transmits at least part of the energy of the percussion piston to the housing, and that the insert is in the housing held by means of a shrinking adhesion connection.