Offset Rock Bit Pull Back Adapter Alignment
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Solution Overview
Problem
In horizontal directional drilling for fiber optic installations, the frequent removal and reinstallation of drill bits for pulling back fiber conduits often result in damage to threaded connections and seals, and the offset attachment points lead to conduit sticking in the borehole wall during retrieval.
Innovation Solution
An offset rock bit with a pull back adapter that has a non-rotating first end connected to the steering face and a second end with a connection member, ensuring the pull back eye is centrally aligned with the drill bit's longitudinal axis, preventing conduit contact with the borehole wall and facilitating smooth retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate pull back device is installed by removing the drill bit, then the drill bit can be replaced with a dedicated pull back device, but this results in damage to threaded connections and seals due to repeated removal and installation
Solution Approach 1:
The patent combines the drill bit and pull back device into a single integrated unit. The drill bit includes a forward end with a pull back eye directly formed on it, allowing the pull back function to be integrated with the drilling function. This eliminates the need to remove and replace separate devices, thereby protecting threaded connections and seals from damage while maintaining operational ease.
Solution Approach 2:
The drill bit is designed to serve multiple functions: it can both drill the borehole and facilitate pull back of the conduit. The pull back eye is directly formed on the forward end of the drill bit housing, enabling the same component to perform both drilling and pull back operations without requiring separate specialized devices.
2Ease of operation
If the pull back attachment is secured at an offset point on the drill bit, then the attachment can be secured to the drill string, but this causes the fiber conduit to cut into the borehole wall and become stuck during pull back
Solution Approach 1:
The patent intentionally creates asymmetry in the drill bit design by offsetting the pull back eye from the longitudinal centerline of the drill bit. This asymmetric positioning allows the pull back force to be applied at an angle that prevents the conduit from contacting and cutting into the borehole wall during retrieval, thereby eliminating the sticking problem while maintaining ease of attachment.
Data Source
AI summary
An offset rock bit (12) has a steering face (28) and a shoe (30) provided by a recess formed into the steering face (28). A slot (66) formed into the shoe (30) for receiving a pull back adapter (50) in a centrally located position in the forward end of the offset rock bit (12). The pull back 5 adapter (50) has a pull back eye (52) with a central axis (62) which is aligned with a centrally disposed longitudinal axis (20) of the offset rock bit (12) and the tool string (10). This aligns the pull back eye (52) of the pull back adapter (50) with a borehole formed using the offset rock bit (12). The pull back adapter (50) also includes side edges (54,56) which are configured for centering the pull back adapter (50) and pull back conduit within the borehole.