Measuring and testing – Liquid level or depth gauge – Hydrostatic pressure type
Reexamination Certificate
2001-08-24
2003-07-22
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Hydrostatic pressure type
C073S299000, C073S313000, C073S723000, C073S745000, C200S061210, C200S0830SA, C200S0830SA, C200S0830SA, C200S190000
Reexamination Certificate
active
06595051
ABSTRACT:
TECHNICAL FIELD
The present invention relates to pressure-responsive systems and components. Specifically this invention relates to devices and systems that sense the level or depth of fluids and responds thereto by triggering switching mechanisms.
BACKGROUND ART
It is often desirable to know information about fluid levels in tanks. Determining fluid levels and controlling fluid levels in tanks, such as in sewage tanks, water cisterns or tanks, and other fluid system and storage vessels, whether enclosed or open and exposed to the environment, has been done in a number of ways. For example, in tanks that are visually accessible, an operator may periodically take visual readings of the fluid level.
Visual readings, however, are often not desirable, in systems where an automatic response is required when the fluid level reaches a certain threshold. In such cases the activation of a pump or valve may be necessary to move more fluid into the vessel or to discharge fluid from the vessel. In systems where visual readings are not available or when an immediate response is required, control systems are typically employed that are responsive to a fluid level indication. Such control systems may illuminate a light on an indicator panel representing the fluid level and/or trip an alarm to notify a human operator that corrective action is required.
Unfortunately having a human operator manually initiate a corrective function may not be desirable due to the repetitive nature of the function or due to the inefficiency of having a human operator in the system. As a result, control and indicator functions are typically handled by electronic control systems which are responsive to one or more switches that are triggered by fluid level or pressure input. For example, in sewage tanks it is well known to use multiple tilt style float switches to control the fluid level. These may be mercury switches or rolling ball switches, where a ball triggers a microswitch within the mechanism. These switches are triggered when the whole switch mechanism tilts downward toward a tethered connection a sufficient amount. Tilt style float switches are typically attached via an anchor tether either directly to the vessel interior wall, or to a bar, rail, or other vertically disposed structural member within the vessel. A plurality of these tilt style float switches are often disposed vertically with each one representing a unique elevation of fluid level within the vessel.
Unfortunately, numerous problems have been encountered with these mechanisms. For example, turbulent conditions within a fluid-holding vessel can negatively impact performance of float switch systems. Such turbulence is often the result of fluidized material inflow and/or pump-discharged fluid material exiting the tank. This turbulence can create undesirable eddies and waves within the tank that can cause tethered tilt style float switches to become entangled, thus preventing them and the system from proper operation. In addition, the turbulence within the tank can cause inadvertent switching and what is often referred to as “contact chatter” of the switches within the tilt style float switch assemblies. Inadvertent switching can cause system inefficiency and degradation, such as a false level reading which causes a pump to turn on or off earlier or later than desired. Such contact chatter can cause the pump, which is responsive to the triggered switch, to cycle inadvertently on and off at a high rate, resulting in undue and undesirable system wear and operation. Consequently there exists a need for a fluid level sensing and control system which is more reliable in turbulent environments.
Other problems that can result from tilt style float switches include the fact that they are disposed adjacent the surface of the fluid material in the sewage tank. Such environments are often highly corrosive and greasy. These tethered switches can become damaged from banging against each other and the tank wall during the turbulent system operation. In addition, the greasy outer surface of the tilt style float switches can cause them to intermittently adhere and even get stuck against the tank wall, thus affecting system performance and reliability. In addition, low pressure sewage system tanks in both residential and commercial use are often of corrugated side wall construction. These corrugations can serve as a series of mini-ledges or shelves to the grease-covered tilt style float switches, thus facilitating their adherence and entrapment. The tilt style float switches can also become corroded. Leaking mercury from some styles of these switches poses a serious environmental and health hazard. Non-mercury versions of the tilt style float switches can similarly be ruined by corrosion of their contact or leads, thus rendering them inoperable. Consequently there exists a need for a fluid level sensing and control system which is more reliable in corrosive, greasy, and/or contaminated environments.
Another type of known switching mechanism performs similarly to the typical toilet, in which a ball floats with the fluid level and closes the valve when the tank is full after the toilet is flushed. In these switching mechanisms, the ball floats on the liquid and bumps switches on and off. As with tilt style float switch assemblies, ball float switching mechanisms can only represent the actual liquid level when the switch is bumped and triggered. Consequently there exists a need for a fluid level sensing and control system which can indicate a range of fluid levels. There also exists a need for a fluid level sensing and control system which can be easily adjusted to change the range of fluid levels being monitored.
Another common problem with all of the aforementioned tilt style float switches, and vertical ball float switches is in servicing these systems. Since they are disposed in sewage tanks or other fluid vessels, servicing them can be a messy, less than ideal, undertaking. Consequently there further exists a need for a fluid level sensing and control system which is easier to service.
DISCLOSURE OF INVENTION
It is an object of the exemplary form of the present invention to provide a fluid level sensing and control system.
It is a further object of the exemplary form of the present invention to provide a fluid level sensing and control system which accurately and reliably indicates fluid levels within a reservoir.
It is a further object of the exemplary form of the present invention to provide a fluid level sensing and control system which accurately and reliably indicates fluid levels within reservoirs with turbulent environments.
It is a further object of the exemplary form of the present invention to provide a fluid level sensing and control system which is operative to reliably indicate fluid levels for reservoirs with corrosive, greasy, and/or contaminated environments.
It is a further object of the exemplary form of the present invention to provide a fluid level sensing and control system which is operative to control the input and/or output of fluids within a reservoir responsive to the fluid level in the reservoir.
It is a further object of the exemplary form of the present invention to provide a fluid level sensing and control system which is easy to configure and service.
It is a further object of the exemplary form of the present invention to provide a fluid level sensing and control system which does not require electrical components disposed within the fluid of the tank.
Further objects of exemplary forms of the present invention will be made apparent in the following Best Modes for Carrying Out Invention and the appended claims.
The foregoing objects are accomplished in an exemplary embodiment of the invention by a pressure activated control apparatus that includes a first resilient member having a first or outer surface exposed to the fluid and is responsive to the fluid pressure to trigger one or more switches of a force translation and switching mechanism. The pressure activated control apparatus includes a second or inner surface exposed to
Chandler Systems, Inc.
Jocke Ralph E.
Parmelee Christopher L.
Walker & Jocke LPA
Williams Hezron
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