Fluid handling – Diverse fluid containing pressure systems – Main line flow displaces additive from shunt reservoir
Patent
1989-11-30
1991-12-03
Walton, George L.
Fluid handling
Diverse fluid containing pressure systems
Main line flow displaces additive from shunt reservoir
4323, 1372361, 137393, 137396, 137403, 141 65, 141198, 406 14, 406192, E03F 100, B65G 5300, F16K 31126
Patent
active
050692437
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to liquid level control systems, and concerns in particular the control of the level of the liquid in temporary storage and transportation systems such as are often found in sewage systems.
REVIEW OF THE PRIOR ART (1)
In a number of fields, including that of sewage collection and disposal, liquid is transported along a pipe from one place (a reservoir of liquid) to another by reduced pressure, or vacuum, applied at the delivery end of the pipe causing ambient pressure in the reservoir, or tank, into which the other end of the pipe projects to force the liquid into and along the pipe. A typical set-up employed in the collection of sewage uses, as a temporary liquid store, a tank having an inlet by which liquid may be fed into the tank and an outlet by which liquid may be withdrawn from the tank, the outlet being connected to a vacuum source via a primary, or interface, valve. This interface valve has a valve control system operating in such a way that in use it opens the valve when the tank fills up (when the liquid in the tank reaches a first predetermined level), allowing the applied vacuum to "suck" the liquid in the tank out via the outlet until the tank is empty (the level of liquid left in the tank has dropped to another, lower, predetermined value), at which the control system shuts off the valve.
In general, the Art of collecting liquids, including sewage, by vacuum is well-known, and various Patents relating thereto have been issued over the past 100 years to Liernur, Le Marchand, Liljendahl, Foreman and Jones, et al. One particular facet of the Art involves the necessary vacuum interface valve control system, and a number of these are documented in U.S. Pat. Nos. 3,777,778 (Janu) and 4,373,838 (Foreman and Grooms), and UK Patent No. 2,149,534 (Sykes). The present invention concerns control of the interface valve.
These prior art valve control systems, sometimes known as liquid level control systems, have generally been constructed from many intricate parts, requiring frequent and costly maintenance (for example, shaft seals). In addition, some of the previous vacuum liquid transport systems experience a problem when the vacuum used to transport the liquid drops to a dangerously low level. It arises in the following manner.
Because vacuum liquid transport systems work on the principle of differential pressure between the atmospheric air and the vacuum in the collector pipe, it follows that the higher the vacuum in the collector pipe the higher will be the transport velocity of the liquid. Now, in an emergency situation, such as if one or more vacuum interface valve were to jam open, the vacuum in the collector pipe would drop to a low level. Were the other vacuum valves in the transport system to be allowed to continue to operate automatically at this low vacuum level, the velocity of the liquid in the collector pipe would drop, and the pipe would quickly fill completely. Once the pipe fills with the liquid the energy available from the vacuum pressure is quickly used up in friction losses, and liquid transport stops. This situation is known as "waterlogging", or "bog down", and the possibility of it occurring can be reduced if the interface valve control system is modified to close the valve, so preventing the ingress of further liquid, when the vacuum level drops below some threshold value. The invention proposes that this be achieved by incorporating into the interface valve control system a secondary valve that is itself vacuum operated--and that, indeed, is actuated by the same vacuum as is applied to the liquid storage tank--the arrangement being such that, if the actuating vacuum drops significantly then the secondary valve operates to close the primary, interface, valve, thus preventing further liquid being drawn into the transport system's collecting pipe, and thus obviating, or at least reducing, the risk of the pipe becoming filled with liquid.
More specifically, the invention suggests that a valve control system for use in a temporary li
REFERENCES:
patent: 3628194 (1971-12-01), Liljendahl
patent: 3777778 (1973-12-01), Janu
patent: 3853138 (1974-12-01), Amren
patent: 3998736 (1976-12-01), Greenleaf, Jr.
patent: 4062377 (1977-12-01), Ward
patent: 4179371 (1979-12-01), Foreman et al.
patent: 4188968 (1980-02-01), Trobaugh et al.
patent: 4373838 (1983-02-01), Foreman et al.
patent: 4603709 (1986-08-01), Huisma
patent: 4691731 (1987-09-01), Grooms et al.
Euro Iseki Limited
Mosely Neal J.
Walton George L.
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