Valves and valve actuation – Tube compressors – Fluid pressure actuated
Reexamination Certificate
2000-08-24
2003-06-10
Scherbel, David A. (Department: 3754)
Valves and valve actuation
Tube compressors
Fluid pressure actuated
C251S175000
Reexamination Certificate
active
06575425
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to an interface valve for vacuum sewer systems. In a vacuum sewer system, wastewater that has been collected in a sump, e.g. in a collection sump, a bowl of a vacuum toilet, or in a urinal or wash basin, is evacuated through the interface valve. When the interface valve opens, atmospheric pressure drives the wastewater through the interface valve and through vacuum pipes towards a vacuum source. Some air is usually admitted after the wastewater has passed. The interface valve is opened and closed by a controller. Typically, the controller and the interface valve are operating pneumatically.
BACKGROUND OF THE INVENTION
A pneumatically operated interface valve has been described in U.S. Pat. No. 4,171,853. This interface valve is a piston valve including a valve body, a plunger, a valve piston and a valve seat. The plunger is connected with a pneumatic operation element, such as a bellow. When vacuum is transmitted from the vacuum source through the controller to the operating element, the plunger pulls the piston from the valve seat and opens the interface valve. When atmospheric air is transmitted to the operating element through the controller, the piston returns to the valve seat thus closing the valve.
Such piston valves are large, expensive and have the additional disadvantage that the piston slams on the valve seat when the valve is closed because the piston is pulled by vacuum force against the valve seat. Fracture of the valve body is a frequent problem. Another problem is that the plunger penetrates a bore of the valve body and moves through the bore. A seal is required, e.g. a lip seal. The seal needs to be frequently greased. Particles in the wastewater can jam and destroy the seal.
OBJECT OF THE INVENTION
Object of the present invention is to provide a pneumatically operated interface valve without the discussed disadvantages of the interface valves of the prior art. In addition, the new interface valve should be small, simple, reliable and inexpensive to manufacture.
SUMMARY OF THE INVENTION
An interface valve according to the present invention has a valve casing with an inflow connection for collected wastewater and an outflow connection to the vacuum source. The valve casing includes a chamber that is either in communication with atmospheric or above-atmospheric pressure, or is in communication with sub-atmospheric (vacuum) pressure. The chamber includes a tube-like elastic element that is axially compressed between the inflow and the outflow connection. The elastic element comprises an inflow nozzle and an outflow nozzle, the inflow nozzle being extended towards the inflow connection of the valve casing, the outflow nozzle being extended towards the outflow connection of the valve casing. The nozzles are connected with each other through a seal section, the seal section consisting of seal strips. The seal strips are pressed against each other, when the chamber is in communication with atmospheric pressure, and removed from each other, when the chamber is in communication with sub-atmospheric pressure.
Each nozzle has two ends, a circular and a linear or approximately linear end. The circular open ends are attached to the inflow connection and the outflow connection respectively. The linear mouth ends of the nozzles are connected with each other.
The seal strips extend along a lateral or transversal axis that is oriented approximately perpendicular to the longitudinal axis of the tube-like elastic element. The seal strips can have a linear or curved shape, a curved shape being preferably convex in the direction to the outflow connection. A curved shape of the seal strips improves tight closing of the interface valve.
The pinch valve, or more specifically the seal strips of the elastic element, are kept tight by axial compression of the tube-like elastic element, unless the elastic element is laterally expanded by vacuum pressure in the chamber surrounding the elastic element. The elastic element is shaped such that the seal strips are laterally pressed against each other by axial compression force exerted on the elastic element. The pinch valve is closed even when both connections and the chamber in the valve casing are in communication with the same pressure, e.g. atmospheric pressure. When vacuum is transmitted through the outflow connection into the outflow nozzle, the outflow nozzle is pulled together and the seal strips at the bottom of the nozzle are tightened. When overpressure is transmitted into the chamber, both nozzles are laterally compressed thus further compressing the seal strips. When vacuum is transmitted into the chamber, the nozzles are laterally pulled and expanded until the seal strips are removed from each other and the interface valve is open.
An axial or longitudinal section through the elastic element shows two isosceles triangles while the elastic element is shut. In other words, the elastic element is shaped like an hourglass. The seal strips extend laterally at a common angle point where both isosceles triangles meet. The nozzles preferably have different lengths, the outflow nozzle being shorter than the inflow nozzle. The isosceles triangles have different heights. The seal strips can have a bead-like reinforcement reducing wear of the seal strips resulting from repeated bending of the seal strips during valve operation. The seal strips may also be provided with seal lips.
A view of the elastic element from a different direction shows two trapezoids, while the elastic element is closed, the trapezoids being connected along a common line. The seal strips extend along this line forming the bottom of both nozzles. This line may be curved, preferably convex towards the outflow nozzle.
The elastic element is made of elastic material, such as natural or synthetic rubber, so that the interface valve can be opened and closed several hundred thousand times without breaking. In addition the elastic material provides for a watertight and airtight seal section.
It is further suggested to reinforce the outflow nozzle. This reinforcement prevents indentation of this nozzle by vacuum suction from the outflow connection, and increases the sealing force between the seal strips. The outflow nozzle could include metallic reinforcement plates or strips at those sections of the nozzle that are shaped like a trapezoid. Alternatively, or in addition, these nozzle sections could be made of particularly thick and strong material. Preferably the outflow nozzle is pre-stressed such that it has a convex cross section when no pressure difference is applied.
The elastic element further comprises a first open end and a second open end, the ends being provided with circular rims. The rims are fixed to the valve casing. The rims may be U-shaped, each rim comprising a peripheral edge. The valve casing may be provided with grooves, the grooves being coaxial with the rims of the elastic element. The connections of the interface valve may be formed by sockets that are fixed to the valve casing, e.g. by solvent welding or by a threaded connection. The elastic rims of the elastic element form seals between the sockets and the valve casing. The rims may have edges that are placed into the grooves. The rims are compressed between the valve casing and the sockets. The distance between the grooves of the valve casing is shorter than the length of the elastic element. The elastic element is axially compressed and shortened when the rims are fixed in the grooved. In other words, the length of the elastic element is shortened while it is attached to the valve casing. Compression stress is transmitted to the seal strips through the nozzles in a direction with an axial and radial component, the radial component laterally pressing the seal strips against each other.
The valve casing preferably comprises threads for the attachment of threaded sockets. The rims of the elastic element are compressed between the casing and the sockets and seal gaps between the sockets and the valve casing. The sockets comprise pipe sections for t
Keasel Eric
Roediger Vakuum- und Maustechnik GmbH
Scherbel David A.
Schwartz Ansel M.
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