Vertical Geophone Spring and Pole Piece Design
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Solution Overview
Problem
Conventional geophones suffer from low sensitivity, harmonic distortion, and limited control over damping due to parasitic flux leakage and geometry constraints, which affect their performance in seismic exploration.
Innovation Solution
The geophone design is enhanced by extending the magnetic pole pieces away from the magnetic center, increasing the axial length of the bobbin and housing, and incorporating a mass tuning coil and a contact spring directly on the lower end cap to improve flux density and damping control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pole pieces are extended away from the magnetic center, then flux density and sensitivity are improved, but the device length increases
Solution Approach 1:
The pole pieces are extended in the axial dimension away from the magnetic center, utilizing the third dimension (axial direction) to increase flux density without significantly increasing the radial or circumferential dimensions. This dimensional approach allows sensitivity improvement while controlling overall device footprint.
Solution Approach 2:
The geometric parameters of the pole pieces are changed by extending their axial length and adjusting their positioning relative to the magnet. This parameter modification optimizes the magnetic flux distribution through the air gap, increasing flux density and consequently improving geophone sensitivity.
2Measurement precision
If the axial length of bobbin and housing is increased, then flux density improves, but the device volume increases
Solution Approach 1:
The increased axial length is concentrated in specific regions where it most effectively improves flux density - namely in the pole piece extensions and the corresponding bobbin sections. Rather than uniformly increasing all dimensions, the design applies length increases locally where magnetic flux optimization is most critical.
3Reliability
If a contact spring is added to form electrical circuit, then electrical connection is improved, but device complexity increases
Solution Approach 1:
The contact spring serves multiple functions simultaneously: it provides electrical connection between the bobbin and the housing, acts as a mechanical support element, and contributes to the damping mechanism. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity while improving electrical connection reliability.
4Manufacturing precision
If mass tuning coil is incorporated, then damping control is improved, but device weight increases
Solution Approach 1:
The mass tuning coil allows precise adjustment of the bobbin assembly's effective mass and damping characteristics through electrical parameters rather than requiring significant changes in physical mass. By varying the electrical current and resistance in the tuning coil, damping can be controlled with high precision without proportionally increasing the overall device weight.
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 design results in a 3 dB increase in sensitivity, reduced harmonic distortion, and precise damping control, enhancing the geophone's ability to detect seismic vibrations with improved signal strength and reduced weight.
Implementation Method 1
As the radial flux lines cut the upper and lower coils 40, 42, an electromotive force is induced in the coils according to Faraday's law.
Implementation Method 2
The frequency springs allow the magnet 14, pole pieces 16, 18, and outer housing 20 to vibrate up and down axially with respect to bobbin 30 while the bobbin remains essentially motionless
Implementation Method 3
Contact spring 36 forces the inner circumference of lower frequency spring 34 to abut lower pole piece 18 in opposition to the force of gravity.
Data Source
AI summary
A vertical geophone that includes a lower frequency spring, which forms part of the geophone electrical circuit, that is positioned directly on the lower end cap This arrangement eliminates the “spring supported by a spring” arrangement of prior art geophones to minimize geophone distortion and simplify tuning of the frequency springs. A contact spring is positioned between the lower frequency spring and the lower pole piece for forming part of the geophone electrical circuit. One surface of contact spring includes a plurality of wiper surfaces that ensure consistent sliding electrical contact against either the bottom surface of the lower pole piece or the upper surface of the lower frequency spring. The obverse surface of the contact spring is preferably spot welded to the other adjacent member.