Micro-Geophone Lipless Pole Piece Adhesive Bonding
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Solution Overview
Problem
Conventional geophones face challenges in miniaturization while maintaining sensitivity and frequency response, as reducing size diminishes the ability to output detectable voltage signals and alters natural frequency response, and manufacturing limitations hinder the design of cost-effective micro-geophones.
Innovation Solution
A micro-geophone design featuring lipless pole pieces, adhesive bonding of pole pieces to the magnet, a novel coil form mounting arrangement with thermoset adhesive fillets, and a two-piece bimetallic coil form to control mass and frequency response, along with a unique housing geometry for maximum dimensions within streamer cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the geophone size is reduced, then the device can be miniaturized for use in streamer cables, but the ability to output detectable voltage signals diminishes
Solution Approach 1:
The patent changes key parameters including using a permanent magnet instead of electromagnetic coils, optimizing the magnet-to-pole piece air gap dimensions, and selecting specific spring constants to maintain sensitivity in a miniaturized configuration
Solution Approach 2:
The patent employs composite construction with a non-magnetic housing, magnetic pole pieces, and inertial mass components made from different materials to achieve both miniaturization and maintained signal output capability
2Volume of moving object
If the geophone size is reduced, then the device can be miniaturized, but the natural frequency response is altered
Solution Approach 1:
The patent carefully adjusts the resonant frequency parameters by selecting specific spring constants and inertial mass values to maintain the desired frequency response characteristics despite the reduced overall device size
Solution Approach 2:
The patent uses frequency-tuned springs that are specifically designed to provide the correct resonant frequency response, allowing the miniaturized geophone to maintain proper dynamic characteristics
3Manufacturing precision
If conventional pole pieces with lips are used, then the magnet is precisely aligned, but the geophone diameter increases
Solution Approach 1:
The patent removes the pole piece lips that extend outward to provide alignment, instead using a different alignment mechanism that does not increase the radial dimensions of the geophone
Solution Approach 2:
The patent introduces adhesive bonding as an intermediary method to achieve precise magnet-to-pole piece alignment without requiring mechanical lips, thereby reducing the overall diameter
4Device complexity
If adhesive bonding is used to attach pole pieces to the magnet, then the assembly is simplified, but manufacturing precision challenges arise
Solution Approach 1:
The patent selects adhesive materials with specific properties (viscosity, curing time, bond strength) and controls application parameters to achieve precise alignment and strong bonding in the miniaturized assembly
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
The solution enables a significantly miniaturized geophone with preserved sensitivity and frequency response tuned for 30 Hertz or lower, while controlling damping and maximizing dimensions for efficient seismic surveys, reducing costs and streamer diameter.
Implementation Method 1
The magnet (14) and pole pieces (16, 18) are received within the outer cylindrical housing (20). In addition to shaping magnetic flux across the air gaps (22, 24)
Implementation Method 2
The frequency-tuned springs (32, 34) allow the magnet (14), pole pieces (16, 18), and outer housing (20) to vibrate up and down coaxially with respect to the coil form (30)
Implementation Method 3
Upper and lower electrical coils (40, 42) are wound about the coil form (30) so as to be located in the upper and lower air gaps (22, 24), respectively
Data Source
AI summary
A micro geophone having pole pieces do not extend out around the sides of the magnet, thereby allowing a reduced geophone diameter for a given magnet diameter. The pole pieces are adhesively bonded to the magnet using an adhesive, which may be made suitably electrically conductive by silver or nickel fillers or non-conductive by mica fillers such as borosilicate glass micro-spheres. Axial space is economized by eliminating traditional spider retaining rings. The spider springs are seated directly against the coil form and secured by adhesive fillets disposed on the outward-facing spring circumferences. The spider springs include circumferential notches to receive adhesive. A two-piece bimetallic coil form of aluminum and a heavier material, joined by adhesive, is provided. Headers are affixed to the housing within the seats by adhesive. A straight or rounded chamfer at each of the geophone ends allows the overall geophone dimensions to be maximized.