Reed switch with shock sensing mass within the glass capsule

Details Reed switch with shock sensing mass within the glass capsule Reed switch with shock sensing mass within the glass capsule

2001-05-18

2001-12-11

Barrera, Ramon M. (Department: 2832)

Electricity: circuit makers and breakers

Special application

Change of inclination or of rate of motion responsive

C200S061530, C335S151000, C335S153000, C335S154000, C335S205000

Reexamination Certificate

active

06329618

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to shock sensors in general and to shock sensors employing a reed switch in particular.
BACKGROUND OF THE INVENTION
Shock sensors are widely used in automobiles to detect the onset of a crash. Typically the magnitude and direction of the crash are sensed by micro-mechanical devices that are fabricated as part of an electronic chip. However, integrated circuit chips and micro-mechanical devices are subject to electromagnetic interference, with the result that sometimes a crash is indicated when no crash event is taking place. Macro scale mechanical shock sensors are employed as a safety device to provide a positive indication that the crash of a given magnitude is occurring. With the assurance that a crash is actually taking place the electronics associated with the micro-mechanical shock sensors can determine the magnitude and direction of the crash and deploy various safety systems in accordance with predetermined or adaptive logic.
Reed switches are often employed in the construction of mechanical shock sensors because of their extreme reliability, low-cost and relatively high current switching capabilities. Reed switches are also hermetically sealed from the atmosphere that contributes to their reliability and makes them suitable for use in hostile environments. Existing shock sensors often employ a second hermetic seal about a shock sensing mass and spring in order to form a shock sensor protected from the environment.
What is needed is a shock sensor which has the reliability of a reed switch and which provides an improvement in cost and packaging size.
SUMMARY OF THE INVENTION
The shock sensor of this invention employs a shock sensing magnetic mass that rides on the inside of the glass tube that is sealed about a reed switch. The reed switch is formed by two reeds, formed on the ends of electrical leads that pass through the sealed ends of the glass capsule. Each lead has a portion within the glass capsule that forms a stop. The stops are positioned between the leads and the reeds making up the reed switch. A first stop on a first lead supports a magnetic sensing mass. A second stop, on a second lead, is positioned opposed to and spaced from the first stop and supports a spring that biases the magnetic sensing mass against the first stop. The first stop is positioned so that the shock sensing magnetic mass when resting against the first stop does not cause the reeds of the reed switch to attract and close. Acceleration which is sufficiently aligned with the glass capsule forming the reed switch causes the sensing mass to accelerate toward the second stop, while the motion of the magnetic sensing mass causes the reed switch reeds to attract and close the reed switch. The entire shock sensing mechanism is hermetically sealed within the glass capsule of the reed switch. The reed switch within the glass capsule detects movement of the shock sensing mass, and provides a closed circuit that is used by the automobile safety system to determine that the shock sensor has detected a crash event.
It is a feature of the present invention to provide a shock sensor where the entire shock sensor mechanism is hermetically sealed.
It is another feature of the present invention to provide a shock sensor of reduced packaging size.
It is a yet further feature of the present invention to provide a shock sensor that can be mounted in the fashion identical to a reed switch with staple formed leads.


REFERENCES:
patent: 3644854 (1972-02-01), Steenmeijer
patent: 5212357 (1993-05-01), Reneau

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