Earth-Boring Bit Cone Arrangement to Reduce Tracking
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Solution Overview
Problem
Existing earth-boring drill bits with rotating cone bits experience tracking issues due to overlapping cutting elements, leading to ridge formation on the borehole bottom, which reduces load on inserts and causes wear.
Innovation Solution
The design features three cones with specific arrangements of cutting elements, including a maximum number of heel row inserts on one cone, 90% as many adjacent row inserts on another, and a staggered configuration with increased pitch in the third cone's heel row to reduce tracking, ensuring adequate support and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the pitch in the overlapping heel row of another cone is increased to break up ridges, then tracking is reduced, but the number of inserts in the adjacent row decreases, reducing durability
Solution Approach 1:
The patent applies different pitch values to different cones' heel rows. Specifically, one cone maintains a standard pitch while another cone's heel row uses an increased pitch (20-50% greater) specifically in the overlapping region. This localized differentiation breaks up ridge formation at tracking points without requiring a global pitch increase that would reduce insert count and durability across all cones.
Solution Approach 2:
The patent creates an asymmetric configuration where not all cones have identical heel row pitch. One cone's heel row has a significantly different pitch than the others, specifically designed to interrupt the tracking pattern. This asymmetry in pitch distribution among cones prevents the symmetric ridge formation that occurs when all cones have uniform pitch, thereby reducing tracking while maintaining adequate insert counts.
2Area of stationary object
If the number of inserts in heel rows is maximized to engage more borehole bottom, then coverage is improved, but tracking increases due to overlapping inserts
Solution Approach 1:
The patent changes the pitch parameter of heel row inserts in specific cones to resolve tracking issues. By increasing the pitch (distance between inserts) in the overlapping heel row of one cone by 20-50%, the insert pattern no longer aligns with other cones, breaking up the tracking effect. This parameter modification allows maximum insert engagement for coverage while eliminating the harmful tracking phenomenon.
Solution Approach 2:
The patent converts the potential harm of overlapping inserts (which cause tracking) into a benefit by deliberately designing the overlap pattern. Instead of avoiding overlap entirely, the patent uses the overlapping region to its advantage by applying a different pitch, which transforms the tracking-prone overlap into a tracking-reducing feature. The overlap area becomes the specific location where pitch differentiation is applied to break ridges.
Data Source
AI summary
An earth boring bit has cutting elements arranged to avoid tracking. The bit has a bit body having a bit axis of rotation. First, second and third cones are rotatably mounted to the bit body, each of the cones having a plurality of rows of cutting elements including a heel row and an adjacent row. The heel row of the first cone has at least equal the number of cutting elements as the heel rows of the other cones. The adjacent row of the second cone has at least 90 percent as many cutting elements as the heel row of the first cone. The heel row of the third cone has a pitch that is in the range from 20-50% greater than the heel rows of the first cone.