Downhole Survey Sensor Indexing Without Slip Rings
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Solution Overview
Problem
Existing downhole surveying tools face challenges in accurately measuring borehole trajectory due to systematic errors in gyroscopes and accelerometers, which require indexing mechanisms that increase cost and complexity, especially in compact designs.
Innovation Solution
A compact indexing apparatus that allows sensor devices like gyroscopes and accelerometers to be indexed about an axis using a drive element with an eccentric configuration, coupled with a pitch drive mechanism and optical alignment system, eliminating the need for a rotary position encoder and slip ring assembly, thereby reducing size and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional indexing mechanism with drive portion on support is used to index sensor devices, then the sensor devices can be positioned at various indexing positions, but the apparatus size and complexity increase
Solution Approach 1:
The drive portion is extracted from the support structure and relocated to the base. This separation removes the complexity of accommodating drive mechanisms within the limited space of the support, while maintaining the indexing functionality. The drive element mounted on the base can index the sensor device without requiring complex integration within the support structure.
Solution Approach 2:
The indexing mechanism utilizes a nested arrangement where the drive element on the base interacts with the indexing head on the support through a cam profile mechanism. The drive pin engages with the cam profile to rotate the indexing head, creating a compact nested configuration that achieves indexing capability without adding external complexity.
2Adaptability or versatility
If a conventional indexing mechanism with drive portion on support is used to index sensor devices, then the sensor devices can be positioned at various indexing positions, but the apparatus size increases
Solution Approach 1:
By extracting the drive portion from the support and placing it on the base, the support structure can be minimized in size. The base provides the driving force without requiring additional space on the support, thereby reducing the overall apparatus volume while maintaining indexing capability.
Solution Approach 2:
The mechanism employs nested components where the drive pin and cam profile are integrated in a compact arrangement. The indexing head rotates on the support while being driven by the base-mounted drive element, creating a space-efficient nested configuration that reduces overall apparatus size.
3Device complexity
If optical alignment system is used instead of rotary position encoder, then measurement precision is improved and device complexity is reduced, but alignment requirements become more stringent
Solution Approach 1:
The optical alignment system replaces complex mechanical position encoding mechanisms with optical detection. This substitution reduces device complexity by eliminating mechanical encoders and their associated components, while the optical system provides precise alignment detection through non-contact methods.
Solution Approach 2:
The optical alignment system acts as an intermediary between the indexing mechanism and the control system. Instead of directly reading mechanical position, the optical system detects alignment through light interaction, providing a simpler interface that reduces overall system complexity while maintaining measurement capability.
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
This solution effectively reduces systematic errors in sensor measurements, enables compact tool design, and maintains electrical connectivity without the need for conventional slip rings, enhancing the accuracy and efficiency of downhole surveying operations.
Implementation Method 1
An optical alignment system is provided for sensing alignment between the drive portion and the driven portion for operative engagement therebetween
Data Source
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AI summary
A down hole surveying tool (10) for directional surveying of boreholes. The tool (10) comprises a body (11) which accommodates a two-axis gyroscope (13) and a two-axis accelerometer (15). The gyroscope (13) and accelerometer (15) are rigidly fixed with respect to each other to provide a composite sensor device (17). The sensor device (17) is supported in a rotary mount (31) for rotation about an indexing axis (4). The sensor device (17) can be indexed about the indexing axis between two indexing positions which are 180 degrees apart. An indexing mechanism (70) is provided for selectively indexing the sensor device (17) about the indexing axis (4). The indexing mechanism (70) comprises a drive portion (71) and a driven portion (72) adapted for selective interaction to impart indexing motion to the sensor device (17). The driven portion (72) is movable into and out of engagement with the drive portion (71) upon rotation of the rotary mount (31) about a pitch axis (1) using a pitch drive mechanism (51).