Down-the-hole drill bit shaft redesign for bending force reduction
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Solution Overview
Problem
Down-the-hole drill bits experience increased material loads and cracking issues due to high drilling forces, particularly during directed drilling, leading to machine failure and loss of the drill bit in the hole.
Innovation Solution
Redistribution of material from the cylindrical rear part of the drill bit to the shaft increases the active force-absorbing area of the splined connector, reducing the drill head's overhang and bending forces without affecting weight or other properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drill head is extended axially to increase drilling capability, then the drilling performance is improved, but the bending forces increase due to increased overhang
Solution Approach 1:
The invention redistributes material from the cylindrical rear part of the drill bit to the shaft in the axial direction, effectively moving material along the length of the drill bit. This dimensional redistribution reduces the overhang length while maintaining the necessary drilling capability, thereby reducing bending forces without sacrificing productivity.
2Strength
If the shaft diameter is increased to reduce bending forces, then the structural strength is improved, but the weight of the drill bit increases
Solution Approach 1:
The invention applies local quality by concentrating material specifically in the shaft region where it is needed for strength, rather than uniformly increasing the entire drill bit. The material redistribution creates a locally optimized structure with enhanced shaft strength while maintaining minimal overall weight.
Solution Approach 2:
The drill bit utilizes composite construction with the shaft formed from material redistributed from the cylindrical rear part, creating a composite structure that optimizes strength-to-weight ratio. The splined connector and shaft form an integrated composite system that provides enhanced mechanical properties.
3Reliability
If the splined connector area is increased to reduce cracking, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The invention merges the shaft and splined connector into an integrated structure, where the material from the cylindrical rear part is redistributed to form both the extended shaft and the splined connector simultaneously. This merging reduces the number of separate components while increasing the active force-absorbing area, thereby improving reliability without proportionally increasing complexity.
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention concerns a drill bit, intended to be used with a down-the-hole drill and comprising a drill head (2) with a front surface provided with drill pins (3) and a shaft (4), whereby the shaft is narrower than the drill head and intended to be inserted in a manner that allows axial sliding into the end of a drill chuck that is a component of a down-the- hole drill and which shaft has a rear end part (6) that is somewhat thickened with a plane striking surface (7) against which a hammer piston (8) that is a component of the down- the-hole hammer drill is arranged to impact, that the drill head when viewed along its axial direction has a cylinder-shaped forward part (20) provided with cuttings channels (22), a rear cylinder-shaped part (21) that is located for the reception of drill cuttings at the same level or somewhat below the bottom (25) of the cuttings channels, whereby the diameter (D1) of the forward part is greater than the diameter (D2) of the rear part. In a drill bit that has high performance and a long useful life, and that is furthermore well-suited to be used for directed drilling, the cylinder-shaped forward part (20) of the drill head (2) has an axial length (L3) from the main plane of the front surface to a shoulder plane (26) located between the drill head (2) and the shaft (4) that is greater than the axial length (L4) of the cylinder-shaped rear part (21) of the drill head.