Fluid handling – Processes – With control of flow by a condition or characteristic of a...
Reexamination Certificate
2000-08-17
2002-10-22
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Processes
With control of flow by a condition or characteristic of a...
C137S205000, C137S907000
Reexamination Certificate
active
06467494
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to vacuum sewer systems. More specifically it is related to an arrangement for the supply of atmospheric air to a pneumatic controller of an interface valve, the arrangement preventing water entering the pneumatic controller.
BACKGROUND OF THE INVENTION
Vacuum sewer systems are an alternative to conventional gravity sewer systems. Vacuum sewer systems are used where conventional systems are expensive due to flat terrain, low housing density, difficult ground conditions, high ground water table, or crossing of water protection areas.
Main components of a vacuum sewer system are:
Collection chambers that are installed in yards or streets and include pneumatic interface valves and controllers; vacuum sewers with systematically arranged high and low points; and a vacuum source, i.e. a vacuum station including vacuum tanks, vacuum pumps and sewage pumps. Fundamentals of vacuum sewer systems are described e.g. in U.S. Pat. No. 3,730,884.
Wastewater flows from houses to the collection chambers. The wastewater is collected in a sump of the collection chamber. A collection chamber also includes an interface valve unit consisting of an interface valve, a pneumatic controller and a sensor pipe. Wastewater that has collected in the sump hydro-statically generates an air pressure in the sensor pipe. This air pressure is transmitted to the controller. The controller opens the interface valve when a certain air pressure is transmitted from the sensor pipe. After wastewater evacuation and drop of sensor pressure, the controller closes the interface valve, but after an additional delay time permitting air admission after wastewater evacuation. The admitted atmospheric air drives the wastewater through the vacuum sewers towards the vacuum station.
A pneumatic controller for a vacuum sewer system was described in U.S. Pat. No. 5,657,784 (The following numerals refer to this U.S. patent). The pneumatic controller
10
includes a three-way valve
20
. The three-way valve
20
either transmits vacuum from a vacuum source to the interface valve to open it, or atmospheric pressure from the environment to close it. The controller includes a control chamber
56
that is evacuated through a control valve
22
when the sensor pressure is sufficient to move a sensor diaphragm
16
and open the control valve
22
. The control chamber
56
is continuously connected to the atmosphere through an adjustable nozzle
64
and a filter element
68
. When the control chamber
56
is evacuated, a control diaphragm
72
is pulled into the control chamber
56
and moves the three-way valve
20
so that it transmits vacuum from the vacuum source to the interface valve thus opening the interface valve. When the wastewater has been evacuated, the sensor pressure drops and the sensor diaphragm
16
returns to its original position. It returns the control valve
22
that shuts the control chamber
56
from the vacuum source. Atmospheric air enters slowly through nozzle
64
into control chamber
56
gradually raising the pressure in the control chamber
56
. The control diaphragm
72
and the three-way valve
20
return to their original positions. Atmospheric air is transmitted through the three-way valve
20
to the interface valve and the interface valve is closed. An evacuation cycle is finished.
Atmospheric air can be supplied to the pneumatic controller and the interface valve through an open lid of the collection chamber. However, when the collection chamber is located at a place where surface water could enter the chamber, the chamber cover must be sealed and atmospheric air supplied through a breather line. The breather line can take atmospheric air directly from the environment, e.g. through an external breather tube extending to a level above the maximum flood level, as shown e.g. in U.S. Pat. No. 4,373,838. Alternatively, the breather line can take atmospheric air from the top of the collection chamber sump. The sump is connected to the atmosphere through a vent stack on the gravity drain between the house and the collection chamber. The vent stack also extends to a level above the maximum flood level.
The controller as described in U.S. Pat. No. 5,657,784 has the disadvantage that air bleeds through the controller (The following numerals refer to this U.S. patent). Atmospheric air continuously flows through the controller while the control valve
22
is open. Atmospheric air enters the control chamber
56
through nozzle
64
while air is simultaneously evacuated from the control chamber
56
to the vacuum source. In addition, a direct connection between the atmosphere and the vacuum source is open while the three-way valve
20
switches from one to another position. In the worst case, the controller bleeds for a long time. This happens when the sensor pressure is sufficient to open the control valve
22
, but the vacuum strength is insufficient to move the three-way valve
20
and open the interface valve.
Bleeding controllers have the great disadvantage that a large air volume flows through the controllers and their nozzle. When the air is warm and humid, and the controller is cooler than the air, water condensation occurs in the controller. The more air flows through the controller, the more water condenses. Water in pneumatic controllers causes them to fail. The danger of water condensation is particularly great when atmospheric air is taken from the sump because the wastewater in the sump can be warm and the air in the sump becomes warm and humid. Failure of sump breathing controllers is very frequent.
An even greater problem with sump breathing controllers can be caused when wastewater aspiration occurs. When the vacuum strength is insufficient to open the interface valve and evacuate the wastewater, the water level in the sump rises further. When the controller bleeds, the top of the sump is evacuated and the water level can rise until it reaches the sump breather line and is aspirated through the controller.
Entrance of water into the controller must be prevented to guarantee reliable operation of the controller. Water entering a breather line could be condensed water, ground water infiltrating into a leaking breather line or, in the worst case, it could be wastewater from the sump.
A sump breather arrangement was described in U.S. Pat. No. 4,691,731 by Grooms et al. This arrangement was unable to prevent wastewater from entering the controller, as discussed in detail in U.S. Pat. No. 5,570,715 by Featheringill and Grooms.
Another sump breather arrangement was described in U.S. Pat. 5,570,715. The controller is a bleeding controller. When control valve
88
is opened by sensor pressure moving sensor diaphragm
86
, atmospheric air is sucked from connection
102
through bores
104
and
106
, chamber
79
, control valve
88
, tubes
120
, chamber
82
and connection
96
to the vacuum source. It has the same disadvantage as all other controllers of the prior art that it provides an open connection through the controller between the atmosphere and the vacuum source when the controller is activated by sufficient sensor pressure. Bleeding leads to evacuation of air from the sump into the controller.
To avoid aspiration of wastewater from the sump, the arrangement according to U.S. Pat. No. 5,570,715 also includes a float valve
250
closing the entrance from the sump to the breather line when the wastewater level in the sump rises to a level close to the entrance into the breather line. A problem with this arrangement is that the float valve can be made inoperable by solids or grease floating on the wastewater in the sump. If the float valve does not completely seal the breather line, wastewater enters the controller. Another disadvantage of the arrangement is that the air in the top of the sump is evacuated through the bleeding controller thus further raising the water level in the sump when the vacuum strength is insufficient to open the interface valve. Another problem is that considerable quantities of condensed water could accumulate in the con
Betz Reinhold
Kolb Claus
Roediger Markus
Michalsky Gerald A.
Roediger Vakuum- und Haustechnik GmbH
Schwartz Ansel M.
LandOfFree
Arrangement in a vacuum sewer system for preventing water... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Arrangement in a vacuum sewer system for preventing water..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Arrangement in a vacuum sewer system for preventing water... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2971171