Low-distortion seismometer

Claim 2

A seismometer including in combination: a cylindrical, tubular casing of magnetic material; flux establishing means comprising, a permanent magnet in said casing, a pole piece at each end of said magnet magnetically coupled with each end of said casing to establish an annular airgap therein; a cover plate at each end of said casing to seal the interior volume thereof; a mass-coil assembly comprising, a pair of coils, each coil being adapted to generate an electric signal when linked by a changing magnetic flux in said airgap, and a hollow cylindrical housing supporting said coils on its outer cylindrical wall, said wall defining a pair of end edges; a pair of springs for supporting said mass-coil assembly in and from said cover plates for relative axial movement in respect to said flux establishing means thereby creating said changing magnetic flux; and a pair of resilient retaining means for frictionally engaging said springs with said end edges whereby said springs and said housing becoMe susceptible of relative rotation.

Claim 3

A seismometer including in combination: a cylindrical, tubular casing of magnetic material; flux establishing means comprising, a cylindrical permanent magnet in said casing, a pole piece at each end of said magnet magnetically coupled with each end of said casing to establish an annular airgap therein; a cover plate at each end of said casing to seal the interior volume thereof; a mass-coil assembly comprising, a pair of similar coils, each coil being adapted to generate an electric signal when linked by a changing magnetic flux in said airgap, a hollow cylindrical housing supporting at each end of its outer cylindrical wall one of said coils, and said housing defining a shoulder at each of its end edges; a pair of disc-type spider springs for supporting said mass-coil assembly in and from said cover plates for relative axial movement in respect to said flux establishing means thereby creating said changing magnetic flux; and a pair of resilient retaining means, each retaining means crampingly retaining one of said shoulders with the outer edge of one of said springs whereby said springs and said housing become susceptible of relative rotation.

Claim 4

A seismometer including in combination: a cylindrical, tubular casing of magnetic material; flux establishing means comprising, a cylindrical permanent magnet in said casing, a pole piece at each end of said magnet magnetically coupled with each end of said casing to establish an annular airgap therein; a cover plate at each end of said casing to seal the interior volume thereof; a mass-coil assembly comprising, a pair of similar coils, each coil being adapted to generate an electric signal when linked by a changing magnetic flux in said airgap, a hollow cylindrical housing supporting at each end of its outer cylindrical wall one of said coils, and said housing defining a shoulder at each of its end edges; a pair of disc-type spider springs for supporting said mass-coil assembly in and from said cover plates for relative axial movement in respect to said flux establishing means thereby creating said changing magnetic flux; and a pair of resilient retaining means, each retaining means crampingly retaining one of said shoulders with the outer edge of one of said springs whereby said springs and said housing become susceptible of relative rotation.

Claim 5

The seismometer of claim 2 wherein said resilient retaining means is an insulating ring having an inner groove defined by a substantially horizontal wall, a substantially vertical wall and a tapered wall.

Claim 6

The seismometer of claim 3 and further including: a pair of outer, annular spring contact elements, each element positioned adjacent to the edge of each spring, and said resilient retaining means crampingly engaging said shoulder, said edge of said spring and said contact element whereby said tapered wall causes said spring to frictionally engage with its mating contact element to provide a good electrical contact therebetween.

Claim 7

The seismometer of claim 4 and further including: a pair of inner spring contact elements, said spring defining a center opening, and each inner spring contact element frictionally engaging the edge of each spring at said center opening.

Claim 8

The seismometer of claim 5 wherein each spring has a preformed stress which causes the spring to frictionally engage its mating inner and outer contact elements.

Claim 9

The seismometer of claim 6 wherein the electric circuit between said coils is established through said springs and said flux establishing means.

Claim 10

The seismometer of claim 7 wherein said springs, said inner and said outer contact elements, and said flux establishing means are symmetrically disposed within said casing.

Claim 11

The seismometer of claim 8 wherein the elements in said casing are stacked during assembly of said seismometer.