Patent ID: 11972916
Assignee: NIPPON ALEPH CO., LTD.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 0:
1. A fall detection sensor, comprising:
a non-magnetic case mounted to an object whose fall is to be detected, the case having a hollow portion created by a recessed curved surface whose diameter increases upward around its central axis and a top surface that liquid-tightly closes the top edge of the curved surface;
a magnet having magnetic poles in its longitudinal direction, or a flat disk-shaped magnet magnetized in its radial direction housed in the hollow portion created by the curved surface and the closed top face of the case;
a magnetic fluid sealed in the hollow portion and magnetically attached to at least both ends of the magnetic poles of the magnet; and
a reed switch arranged so that its contact comes at or around the center of the bottom of the case, wherein
the recessed curved surface has a hemisphere having a constant radius of curvature,
when the object is in upright state, the central axis of the case extends in a vertical direction, the magnet whose magnetic poles are covered with the magnetic fluid is gravitationally positioned so that its magnetization direction extends approximately in parallel to the longitudinal direction of the reed switch around the central axis at the lowest position of the curved surface of the case, and each magnetic pole of the magnet respectively magnetizes a corresponding reed of the reed switch positioned immediately below the magnet, thus allowing one of the reeds of the reed switch to be magnetized to N pole, whereas the other reed to be magnetized to S pole, to attract each other, and turning on the reed switch, and
when the object inclines from the upright state, the magnet slides following the tilt direction and tilt angle along the curved surface having the hemisphere with the constant radius of curvature, deviating from the central axis of the case and allowing only one of the magnetic poles of the magnet to be positioned around the central axis, and thus the magnetic poles magnetize each reed of the reed switch to the same pole, turning off the reed switch with respect to all inclination directions of the object.