Drill Bit Assembly Axial Removal Mechanism
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Solution Overview
Problem
Conventional drill bit assemblies for down-the-hole hammers require unscrewing the chuck from the wear sleeve for bit replacement, which is time-consuming and difficult due to high torque, often necessitating specialist equipment and reducing drilling efficiency.
Innovation Solution
A drill bit assembly design that allows bit removal without unscrewing the chuck from the wear sleeve, utilizing axially extending splines and alignment splines to transition the bit from a retained to a removable position while the chuck remains engaged, enabling axial movement and rotational disengagement for easy bit replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the chuck is unscrewed from the wear sleeve for bit replacement, then the bit can be removed from the chuck, but the operation becomes time-consuming and requires specialist break-out equipment due to high torque
Solution Approach 1:
The bit retention mechanism is segmented into two independent functions: the chuck-splines connection for rotational drive, and the retaining ring-shoulder connection for axial retention. This allows the bit to be retained during drilling while enabling removal by simply moving the bit axially without unscrewing the chuck from the wear sleeve.
Solution Approach 2:
The bit retention function is extracted from the chuck-wear sleeve threaded connection and assigned to a separate retaining ring mechanism. This extraction allows bit removal to occur independently of the chuck's threaded connection to the wear sleeve, eliminating the need for break-out equipment.
2Ease of operation
If a retaining sleeve is mounted externally on the chuck to enable bit removal without unscrewing, then bit replacement becomes easier, but flushing issues arise with the retention sleeve
Solution Approach 1:
The retention function is extracted from a complex external retaining sleeve and assigned to a simple internal retaining ring mechanism that works with the bit's shoulder. This simplified design eliminates flushing issues while maintaining ease of bit removal.
Solution Approach 2:
The design uses simple, inexpensive components (retaining ring and shoulder) instead of a complex retaining sleeve. The bit itself can be easily replaced or reground, making the system favor simple, disposable-like components over complex, maintenance-prone ones.
Data Source
AI summary
The present invention relates to a drill bit assembly for fluid-operated percussion drill tools. The drill bit assembly comprises a percussion bit having a head portion formed with an axially extending shank, a first plurality of axially extending splines on the shank slideably engageable with a first plurality of complementary splines formed internally of a drive chuck whereby rotational drive from the chuck may be transmitted to the shank. The assembly also comprises engagement means on the chuck adapted for connecting the chuck to a drive means of the fluid-operated percussion drill tool. During drilling, the bit and the chuck are held in a first relative orientation in which the bit is retained in the chuck, and the bit is moveable axially relative to the chuck to a bit removal position, in which the bit is rotatable relative to the chuck to a second relative orientation in which the bit is removable from the chuck. The bit is moveable to the bit removal position while the chuck is fully engaged with the drive means.