Micro-Geophone Lipless Pole Pieces and 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 suppress eddy currents, allowing for reduced size without compromising sensitivity or frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the geophone size is reduced, then miniaturization is achieved and operational costs are reduced, but the ability to output detectable voltage signals diminishes and sensitivity is compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the mass of the coil form assembly through material selection (aluminum vs. brass) and dimensional adjustments. This allows optimization of the voltage output signal strength while maintaining the miniaturized geophone size, directly resolving the contradiction between small size and detectable signal output.
Solution Approach 2:
The patent uses composite materials by offering coil forms made from different materials (aluminum or brass) with distinct properties. Aluminum provides lightweight construction for sensitivity, while brass offers higher density for mass control. This material composite approach enables fine-tuning of the geophone's electrical and mechanical characteristics to maintain signal detectability in a miniaturized design.
2Volume of moving object
If the geophone size is reduced, then miniaturization is achieved, but the natural frequency response is altered and sensitivity at frequencies of 30 Hertz or lower is compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the mass of the coil form assembly through material selection (aluminum vs. brass) and dimensional adjustments. This allows optimization of the voltage output signal strength while maintaining the miniaturized geophone size, directly resolving the contradiction between small size and detectable signal output.
Solution Approach 2:
The patent applies preliminary anti-action by proactively designing the coil form mass and material properties to counteract the negative effects of miniaturization on frequency response. By pre-calculating and pre-adjusting the mass parameters before manufacturing, the design compensates for potential frequency response degradation, ensuring sensitivity at frequencies of 30 Hertz or lower is maintained despite the reduced size.
3Stability of the object's composition
If traditional pole piece lips are used for alignment, then coaxial alignment is achieved, but the geophone diameter increases
Solution Approach 1:
The patent applies the extraction principle by removing the traditional pole piece lips that extended radially outward for alignment purposes. Instead, the invention uses a streamlined pole piece design where alignment is achieved through alternative means (such as precision machining of the pole piece body or magnetic centering), eliminating the need for protruding lips and thereby reducing the overall geophone diameter while maintaining coaxial alignment stability.
4Ease of manufacture
If adhesive bonding is used for pole pieces and coil form mounting, then manufacturing complexity is reduced and cost is decreased, but bonding precision and structural integrity must be maintained
Solution Approach 1:
The patent applies mechanics substitution by replacing traditional mechanical fastening methods (such as screws, clips, or retaining rings) with adhesive bonding for mounting the pole pieces and coil form. This substitution simplifies the manufacturing process by eliminating complex mechanical assemblies and reduces production costs, while the adhesive provides sufficient bonding precision and structural integrity for the geophone's operational requirements.
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 design achieves significant miniaturization while maintaining sensitivity and frequency response, particularly for frequencies of 30 Hertz or lower, and allows for increased geophone length and diameter within streamer cables, reducing operational costs.
Implementation Method 1
The magnet (14) and pole pieces (16, 18) are received within the outer cylindrical housing (20)... shaping magnetic flux across the air gaps (22, 24)... The magnet (14) and pole pieces (16, 18) form a magnetic circuit
Implementation Method 2
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)... As the radial flux lines cut the upper and lower coils (40, 42), changes in flux density induce an electromotive force in the coils according to Faraday's law
Implementation Method 3
The upper and lower 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)... The frequency-tuned springs (32, 34) are designed and tuned to provide a desired resonant frequency
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.