Convex Crested Insert with Deflected Wedge Surfaces for Drilling
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Solution Overview
Problem
Prior art roller cone bit inserts with deflected wedge surfaces fail to simultaneously effectively break bottom hole rocks and gouge borehole walls due to a blunter top surface and smaller contact area, leading to low rate of penetration and reduced bit durability.
Innovation Solution
A convex crested insert with deflected wedge surfaces, featuring a conical crest base, a smooth convex top surface, and tapered wedge surfaces, which provides a higher middle contact point for rock breaking and increased contact area for gouging, reducing stress concentration and edge effects while maintaining a larger contact area with the borehole wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If inserts with deflected wedge surfaces are used, then contact area with borehole wall is larger and gouging action is improved, but top surface becomes blunter and rock breaking ability deteriorates
Solution Approach 1:
The insert top surface is designed with different local geometries: a convex central portion for concentrated rock breaking and deflected wedge surfaces at the sides for gouging action. This local differentiation allows each region to perform its specific function optimally without compromising the other.
Solution Approach 2:
The insert top surface is segmented into a central convex portion and side wedge portions. The central portion has a different geometric configuration (convex with radius R1) compared to the side portions (deflected wedge surfaces with angle α), allowing independent optimization of rock breaking and gouging functions.
2Strength
If conical spherical inserts are used, then top surface is sharper and rock breaking is improved, but contact area with borehole wall becomes smaller and gouging action weakens
Solution Approach 1:
The insert combines a convex central portion for rock breaking with deflected wedge surfaces for gouging. The central convex area provides the necessary sharpness for rock penetration, while the extended wedge surfaces at the sides increase contact area with the borehole wall for effective gouging action.
Solution Approach 2:
The insert merges two previously separate insert types (spherical for rock breaking and deflected wedge for gouging) into a single hybrid design. The central convex portion handles rock breaking while the side wedge surfaces handle gouging, allowing both functions to be performed simultaneously by one insert.
3Ease of manufacture
If plain top surface is used, then manufacturing is simpler, but edge effects cause higher stress concentration and reduced working life
Solution Approach 1:
The insert top surface features a convex central portion with a curved surface of radius R1 instead of a plain flat surface. This curvature eliminates stress concentration at the center, distributing stresses more evenly across the top surface and preventing premature failure at the highest stress points.
Data Source
AI summary
This invention relates to carbide inserts used on roller cone bits for oil and gas drilling applications as well as for other geological drilling applications, and more specifically, relates to the convex crested insert with deflected wedge surfaces. The insert comprises a cylindrical portion and a crest portion. Said crest portion is composed of a conical crest base, a top surface and two opposing wedge surfaces. Upper ends of the two wedge surfaces are merged smoothly with top surface of the insert. The specific feature of the structure is that top surface of the crest portion is convexed outwardly and forms a smooth curve surface which is higher in the middle and lowers down gradually to each end. Said two wedge surfaces are slant wedge surfaces, so that a width of the top surface and therefore a width of the insert crest are tapered from one end to the other. Advantages of this invention include: 1. Help for rock breaking and therefore, it can increase drilling efficiency of the cutters and lower the overall drilling cost; 2. higher anti-breakage capability and longer working life; and 3. when inserts of this invention are used as heel row cutting elements on bit, contact area between wider end of the top surface of the insert and borehole wall is larger and therefore the gouging action applied on the borehole wall is higher and can also achieve better gage protection of the bit.