Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-09-30
2001-05-22
Lefkowitz, Edward (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S624000, C073S314000, C116S109000
Reexamination Certificate
active
06236323
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to the field of fluid level indicating devices and, in particular to, a fluid level indicator that utilizes a plurality of magnetic pins to visually indicate fluid level in a fluid containing chamber having a piston.
BACKGROUND OF THE INVENTION
Without limiting the scope of the invention, its background will be described with reference to a hydraulic chamber in an aircraft as an example.
In an aircraft hydraulic system, hydraulic fluid supply and pressure is maintained using a hydraulic reservoir. The typical reservoir design incorporates a moving piston in a chamber to accommodate changes in reservoir volume. The reservoir volume will change as a result of temperature fluctuations, system leaks and differential actuator fluid exchange. The piston position in the chamber changes proportional with the change in reservoir fluid level. By measuring the position of the piston in the chamber, the fluid level in the reservoir can be measured.
In one system, fluid level may be indicated using a graduated rod attached to the piston that extends outwardly from the chamber. It has been found, however, that the rod must be equal in length to the entire piston travel in order to provide the required fluid level readings. Due to space limitations in many aircrafts, however, using a rod to indicate fluid level in the hydraulic reservoir is impractical.
To overcome these space constraints, attempts have been made to design a fluid level indicator for the hydraulic reservoir of an aircraft that does not require additional space next to the reservoir piston. For example, in one design, an indicator tube is mounted adjacent to the hydraulic reservoir that has a floating indicator disposed therein. The floating indicator is tied directly to the piston using a pulley and cabling system. It has been found, however, that like the graduated rod level indicator, having the level indicating device attached directly to the piston may induce failures in the reservoir piston if the level indicating device becomes restricted from moving or jammed. Additionally, it has been found that the accuracy of such devices may be affected by the high vibration, high shock loads and high g-forces experienced in certain aircraft.
Therefore, a need has arisen for a fluid level indicator for indicating the level of a fluid in a chamber having a piston. A need has also arisen for such a fluid level indicator that is not physically tied to the reservoir piston. Further, a need has arisen for a such a fluid level indicator that does not require substantial space next to the chamber.
SUMMARY OF THE INVENTION
The present invention disclosed herein provides a fluid level indicator for indicating the level of a fluid in a chamber having a piston. The fluid level indicator of the present invention accurately indicates the level of the fluid in the chamber without being physically connected to the piston and without requiring substantial space next to the chamber. Additionally, the fluid level indicator of the present invention is unaffected by high vibration, high shock loads or high g-forces.
The fluid level indicator comprises a housing that is positioned adjacent to the chamber. Disposed within the housing are a plurality of magnetic pins. The magnetic pins move between a first position and a second position. Springs bias each of the magnetic pins toward the first position. To overcome the spring bias force, a metallic band is wrapped around the piston such that when the piston is aligned with one of the magnetic pins, that magnetic pin is shifted to the second position. A viewing window is attached to the housing such that the position of the magnetic pins may be viewed therethrough, thereby indicating the position of the piston within the chamber and indicating the level of fluid within the chamber.
The viewing window includes indicia specifying the level of fluid in the chamber. The viewing window may be frosted such that magnetic pins in the first position are seen through the viewing window and magnetic pins in the second position are not seen through the viewing window. Alternatively, the viewing window may be clear such that a first color is viewable when the magnetic pins are in the first position and a second color is viewable when the magnetic pins are in the second position. In this embodiment, the magnetic pins each have a polished button attached thereto.
In one embodiment, a booster magnet may be added that contacts the metallic band to increase the force attracting the magnetic pins toward the second position when piston is aligned therewith.
REFERENCES:
patent: 3964312 (1976-06-01), Sebek
patent: 3965317 (1976-06-01), Gratzmuller
patent: 4289451 (1981-09-01), Lewis
patent: 4489224 (1984-12-01), Steer
patent: 4804944 (1989-02-01), Golladay et al.
patent: 4870862 (1989-10-01), Bonetti
patent: 5056049 (1991-10-01), O'Neill
patent: 5136884 (1992-08-01), Lovett
Bryan Darrel Bill
Fenny Carlos Alexander
Bell Helicopter Textron Inc.
Emanuelson Kenneth T.
Gardere Wynne & Sewell LLP
Lefkowitz Edward
Warren, Jr. Sanford E.
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