Flow, tactile and orientation sensors using deformable...

Details Flow, tactile and orientation sensors using deformable... Flow, tactile and orientation sensors using deformable...

1998-12-08

2001-03-20

Noori, Max (Department: 2855)

Measuring and testing

Dynamometers

Responsive to force

C073S777000

Reexamination Certificate

active

06202495

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
Flow sensors and tilt sensors are known in the art, and are used in a wide variety of applications. The sensors tend to be bulky, expensive and take up valuable space within the settings they are used in. It would be desirable to have a flow or tilt sensor which is small in size, easy to manufacture and use while being more cost effective. It would further be desirable to have such a sensor which is also useable in harsh environments.
BRIEF SUMMARY OF THE INVENTION
A microelectric flow sensor including a deformable mechanical element is disclosed. The sensor includes a beam element mounted to a substrate. The beam element is anchored to the substrate on a first end, and deformed to a position normal to the surface of the substrate. An electrode is positioned on the substrate below a portion of the beam, such that when the beam is deflected, an electrical connection is established between the beam and the electrode.
Further embodiments include a beam element which includes a sensing beam surrounded by at least two cantilever beams which act as switches. The sensing beam is defined with two mechanically weak points which allow the sensing beam to be mechanically deformed to a new position approximately perpendicular to the cantilever beams and the top surface of the substrate. The substrate also includes electrodes which are positioned underneath the ends of the cantilever beams. With the sensing beam perpendicular to the surface, forces applied to the sensing beam will cause the beam to deflect. Because the cantilever beams are mechanically connected to the sensing beam the cantilever beams are bent towards a substrate upon deflection of the sensing beam. Eventually, the cantilever beams switch contacts will contact the electrodes on the substrate creating a short circuit between the electrodes. Accordingly, the microelectric sensor provides an “on” or “off” signal dependent upon the force of the flow on the sensing beam. The flow threshold that is detected by the sensor is directly proportional to the stiffness and length of the beams.
In one embodiment the beam element of the sensor is formed having a plurality of cantilever beams of various lengths. The longer cantilever beams will be more sensitive since a smaller deflection by the sensing beam is required to produce an electrical connection between pairs of electrodes associated with the longer cantilever beams. Alternatively, a beam element including a single cantilever beam with multiple contacts and associated electrodes could be utilized to accomplish the same function.
The flow sensor may be configured to function as a tilt sensor by attaching a weight proximate the end of the sensing beam. In the single beam embodiment, tilting the beam beyond a certain angle causes the weight to deflect the beam into a position wherein the beam is in electrical communication with the electrode. In the multiple beam embodiments, tilting of the sensor beyond a certain angle will cause the weight to deflect the sensing beam, which produces a concomitant deflection of the cantilever beams such that the cantilever beams contact the associated electrodes on the substrate. The tilt sensor can be made to sense various angles by changing the original angle to which the beam is bent. Further, by orienting several sensing beams at different angles on the substrate, tilt measurements on a solid angle are possible.
The flow sensor can be further modified to perform in harsh environments by including a diaphragm surrounding the cantilever beams and electrodes, with the sensing beam extending therethrough. The area surrounding the cantilever beams and electrodes which is defined by the diaphragm may be filled with a nonconductive liquid, a gas or be evacuated before being sealed. With such an embodiment, only the sensing beam is exposed to the environment, while the cantilever beams and associated electrodes are insulated from the environment.


REFERENCES:
patent: 5397904 (1995-03-01), Arney et al.
patent: 5490034 (1996-02-01), Zavracky et al.
patent: 5526703 (1996-06-01), Aslam et al.
patent: 5880921 (1999-03-01), Tham et al.

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