Hall-effect seat belt tension sensor

A tension sensor for a seatbelt comprising:

• an upper housing having a pair of spaced, integral seatbelt guides depending therefrom;
• a lower housing secured to said upper housing having a pair of spaced, integral seatbelt guides depending therefrom, the seatbelt guides lying in spaced relation to the seatbelt guides of said upper housing;
• a plunger housing depending from said lower housing between the seatbelt guides thereof, said plunger housing having an orifice therein defined by a housing lip portion;
• a plunger disposed within the orifice of said plunger housing having an upper portion shaped to allow said seatbelt to move thereacross and a lower portion having a lip depending therefrom that engages the plunger housing lip portion thereby securing said plunger in said plunger housing;
• a plurality of springs disposed between said plunger and said lower housing for biasing said plunger toward said upper housing;
• a permanent magnet secured at a point to said plunger;
• and
• a Hall effect sensor secured to said lower housing at a point wherein the magnetic flux of said permanent magnet varies through said Hall effect sensor when said plunger is biased toward said lower housing, said Hall effect sensor having an output responsive to the magnetic flux therein.

A tension sensor for a seatbelt comprising:

• a base having a pair of spaced seatbelt guides, each having a slot therein for acceptance of said seatbelt;
• a right circular cylindrical plunger housing having an open upper end and a lower end secured to said base between the pair of seatbelt guides, said housing having a plurality of detent slots therein;
• a plunger having an upper portion shaped to allow said seatbelt to move thereacross and a right circular cylindrical lower portion having a plurality of detents depending therefrom, the lower portion disposed within said plunger housing wherein the detent slots thereof are engaged by the detents of said plunger lower portion;
• a belleville spring disposed between said plunger lower portion and said base for biasing said plunger upwardly, away from said base;
• a permanent magnet secured at a point to said plunger;
• and
• a Hall effect sensor secured at a point to said base wherein the magnetic flux of said permanent magnet varies through said Hall effect sensor when said plunger is biased toward said base, said Hall effect sensor having an output responsive to the magnetic flux therein.