# US 2014/0022866 A1 · Micro-geophone > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0022866 A1 - Document ID: US20140022866A1 - Status: Published application - Kind: A1 - Application number: 13/553,502 - Filed: 2012-07-19 - Published: 2014-01-23 - Earliest claimed: 2012-07-19 - Assignees: Geospace Technologies Corporation - Inventors: DANIEL M. WOO - Web page: https://patentgrep.com/patent/US20140022866A1 ## CPC - G01V 1/182: {with moving coil} - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract 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. ## Claims ### Claim 1 A geophone (110) comprising: a cylindrical magnet (114) defining a circumference and first and second ends; first and second pole pieces (116, 118) disposed at the first and second ends of said magnet, respectively, each of said first and second pole pieces (116, 118) characterized by having no lip that surrounds the circumference of said magnet; a tubular outer cylinder housing (120), said magnet (114) and first and second pole pieces (116, 118) being coaxially received within and connected to said housing (120); and an electrical coil assembly disposed between said magnet (114) and said housing (120) and movable in an axial direction with respect to said housing (120). ### Claim 2 (depends on 1) The geophone (110) of claim 1 further comprising: a first adhesive bond between said magnet (114) and said first pole piece; and a second adhesive bond between said magnet and said second pole piece. ### Claim 3 (depends on 2) The geophone (110) of claim 2 wherein: said first and second adhesive bonds are electrically conductive. ### Claim 4 (depends on 3) The geophone (110) of claim 3 wherein: said first and second adhesive bonds each include an epoxy and a metallic filler. ### Claim 5 (depends on 2) The geophone (110) of claim 2 further comprising: a first lead (164) electrically connected to a first end of said electrical coil assembly via said first pole piece, said magnet, and said second pole piece; and a second lead (160) electrically connected to a second end of said electrical coil assembly. ### Claim 6 (depends on 5) The geophone (110) of claim 5 wherein: said electrical coil assembly includes a coil (140, 142) wound about a coil form (130), a first spring (132) connected between a first end of said coil form and said first pole piece, and a second spring (134)connected between a second end of said coil form and said second pole piece. ### Claim 7 (depends on 6) The geophone (110) of claim 6 further comprising: an electrical insulator disposed between said first pole piece and said first spring. ### Claim 8 (depends on 7) The geophone (110) of claim 7 wherein: said first lead makes sliding electrical contact with said first pole piece; said second spring makes sliding electrical contact with said second pole piece; and said second lead makes sliding electrical contact with said first spring. ### Claim 9 (depends on 2) The geophone (110) of claim 2 wherein: said first and second adhesive bonds are dielectric. ### Claim 10 (depends on 9) The geophone (110) of claim 9 wherein: said first and second adhesive bonds each include an epoxy and an insulating filler. ### Claim 11 (depends on 9) The geophone (110) of claim 9 wherein: said electrical coil assembly includes a coil (140, 142) wound about a coil form (130), a first spring (132) connected between a first end of said coil form and said first pole piece, and a second spring (134)connected between a second end of said coil form and said second pole piece; and said geophone further comprises a first lead that makes sliding electrical contact with said first spring and a second lead that makes sliding electrical contact with said second spring. ### Claim 12 (depends on 1) The geophone (110) of claim 1 further comprising: a protrusion (392) formed in said magnet (114); and a recess (396) formed in said first pole piece so as to receive said protrusion and coaxially align said magnet with said first pole piece. ### Claim 13 (depends on 12) The geophone (110) of claim 12 further comprising: a first adhesive bond between said magnet (114) and said first pole piece; and a second adhesive bond between said magnet and said second pole piece. ### Claim 14 (depends on 1) The geophone (110) of claim 1 further comprising: a protrusion (398) formed in said first pole piece; and a recess (394) formed in said magnet (115) so as to receive said protrusion and coaxially align said magnet with said first pole piece. ### Claim 15 (depends on 14) The geophone (110) of claim 14 further comprising: a first adhesive bond between said magnet (114) and said first pole piece; and a second adhesive bond between said magnet and said second pole piece. ### Claim 16 A geophone (110) comprising: a cylindrical magnet (114) defining a circumference and first and second ends; first and second pole pieces (116, 118) disposed at the first and second ends of said magnet, respectively, each of said first and second pole pieces (116, 118) characterized by having no lip that surrounds the circumference of said magnet; and an electrical coil assembly movably disposed around said first and second pole pieces. ### Claim 17 (depends on 16) The geophone (110) of claim 16 further comprising: a first adhesive bond between said magnet (114) and said first pole piece; and a second adhesive bond between said magnet and said second pole piece. ### Claim 18 (depends on 17) The geophone (110) of claim 17 wherein: each of said first and second adhesive bonds includes at least one from the group consisting of an epoxy, a metal filler, and an insulating filler.