Geophone having improved sensitivity
First Claim
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1. A geophone (110) comprising:
- a cylindrical magnet (114) having a length-to-diameter ratio (lm/dm) greater than 0.5 and less than 1.0;
upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively, said upper and lower pole piece caps (116, 118) together defining an overall longitudinal pole-to-pole length (lpp) and a parasitic air gap (125) therebetween having a longitudinal air gap length (lg), said upper and lower pole piece caps (116, 118) having a parasitic gap length to pole-to-pole length ratio (lg/lpp) greater than 0.25;
a tubular outer cylinder housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120); and
an electrical coil (140, 142) disposed between said magnet (114) and said housing (120) and movable in an axial direction with respect to said housing (120).
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Accused Products
Abstract
A geophone utilizing an Alnico-9 magnet and having an improved sensitivity over Alnico-9 geophones of prior art through the lengthening of the parasitic air gap between the upper and lower pole pieces which, results in less magnetic flux leakage. The flux concentration through the geophone coils is increased and shifted towards the ends of the magnet. The increase of sensitivity of geophone of the present invention over prior art geophones may exceed 3 dB. The axial length of the coil bobbin is increased, and the positions of the electrical coils are moved towards the ends of the magnet to align with the shifted magnetic flux.
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Citations
26 Claims
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1. A geophone (110) comprising:
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a cylindrical magnet (114) having a length-to-diameter ratio (lm/dm) greater than 0.5 and less than 1.0; upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively, said upper and lower pole piece caps (116, 118) together defining an overall longitudinal pole-to-pole length (lpp) and a parasitic air gap (125) therebetween having a longitudinal air gap length (lg), said upper and lower pole piece caps (116, 118) having a parasitic gap length to pole-to-pole length ratio (lg/lpp) greater than 0.25; a tubular outer cylinder housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120); and an electrical coil (140, 142) disposed between said magnet (114) and said housing (120) and movable in an axial direction with respect to said housing (120). - View Dependent Claims (2, 3, 4, 5, 6)
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7. A geophone (110) comprising:
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a cylindrical magnet (114) having a length-to-diameter ratio (lm/dm) greater than 0.5 and less than 1.0; upper and lower pole piece (116, 118) caps receiving the upper and lower ends of said magnet (114), respectively, said upper and lower pole piece caps (116, 118) together defining a parasitic air gap (125) therebetween having a longitudinal parasitic gap (125) length (lg); a tubular outer cylindrical housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively, each of said upper and lower annulus air gaps (122, 124) having a radial air gap dimension (ra), a parasitic gap length to radial air gap ratio (lg/ra) being greater than 4.0; and an electrical coil (140, 142) assembly disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120). - View Dependent Claims (8, 9, 10, 11, 12)
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13. A geophone (110) comprising:
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an Alnico-9 cylindrical magnet (114); upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet (114), respectively, said upper and lower pole piece caps (116, 118) together defining a parasitic air gap (125) therebetween having a longitudinal parasitic gap length (lg), said upper and lower pole piece caps (116, 118) each defining a longitudinal pole length (lp) and a lip thickness (tl); a tubular outer cylindrical housing (120), said magnet (114) and said upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively, each of said upper and lower annular air gaps (122, 124) having a radial air gap dimension (ra); and an electrical coil assembly (140, 142) disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120); wherein said geophone (110) is arranged so that the relation - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A geophone magnetic field subassembly comprising:
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a cylindrical magnet (114) having a length-to-diameter ratio (lm/dm) greater than 0.5 and less than 1.0; and upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively, said upper and lower pole piece caps (116, 118) together defining an overall longitudinal pole-to-pole length (lpp) and a parasitic air gap (125) therebetween having a longitudinal air gap length (lg), said upper and lower pole piece caps (116, 118) having a parasitic gap length to pole-to-pole length ratio (lg/lpp) greater than 0.25.
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22. A geophone (110) comprising:
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an Alnico-9 cylindrical magnet (114) defining an axial magnet length (lm); upper and lower pole piece (116, 118) caps receiving the upper and lower ends of said magnet (114), respectively, said upper and lower pole piece caps (116, 118) defining a pole thickness (tp) such that a ratio of said pole thickness to magnet length (tp/lm) is greater than 0.15; a tubular outer cylindrical housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively; and an electrical coil (140, 142) assembly disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120).
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23. A geophone (110) comprising:
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a cylindrical magnet (114); upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively, said upper and lower pole piece caps (116, 118) together defining a parasitic air gap (125) therebetween having a longitudinal air gap length (lg); a tubular outer cylindrical housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively, each of said upper and lower annulus air gaps (122, 124) having a radial air gap dimension (ra) such that a ratio of said air gap length to said radial air gap dimension (lg/ra) is greater than 5.7; and an electrical coil (140, 142) assembly disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120).
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24. A geophone (110) comprising:
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a cylindrical magnet (114); upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively; a tubular outer cylindrical housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively, each of said upper and lower annulus air gaps (122, 124) having a radial air gap dimension (ra), the region of said housing between said upper and lower annulus air gaps (122, 124) defining a housing wall thickness dimension (th) such that a ratio of said housing wall thickness dimension to said radial air gap dimension (th/ra) is greater than 0.7; and an electrical coil (140, 142) assembly disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120).
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25. A geophone (110) comprising:
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a cylindrical magnet (114); upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively, said upper and lower pole piece caps (116, 118) defining a pole length (lp) and a lip length (ll) such that a ratio of said pole length to said lip length (lp/ll) is greater than 2.1 and less than 5.0; a tubular outer cylindrical housing (20), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively; and an electrical coil (140, 142) assembly disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120).
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26. A geophone (110) comprising:
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a cylindrical magnet (114) having a length-to-diameter ratio (lm/dm) greater than 0.5 and less than 1.0; upper and lower pole piece caps (116, 118) receiving the upper and lower ends of said magnet, respectively, said upper and lower pole piece caps (116, 118) defining a pole length (lp) and a lip length (ll) such that a ratio of said pole length to said lip length (lp/ll) is greater than 1.7; a tubular outer cylindrical housing (120), said magnet (114) and upper and lower pole piece caps (116, 118) being coaxially received within and connected to said housing (120), said housing (120) and said upper and lower pole piece caps (116, 118) together defining upper and lower annular air gaps (122, 124), respectively; and an electrical coil (140, 142) assembly disposed in said upper and lower annular air gaps (122, 124) and movable in an axial direction with respect to said housing (120).
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Specification