Valves and valve actuation – Pivoted valves – Gate
Reexamination Certificate
1997-05-05
2001-12-04
Rivell, John (Department: 3753)
Valves and valve actuation
Pivoted valves
Gate
C251S301000
Reexamination Certificate
active
06325356
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to vacuum toilet systems for aircraft, and, more particularly, to discharge valves with rotary gates in such systems.
Lavatories having vacuum toilet systems have been used in aircraft for many years. One such vacuum toilet system has a waste-receiving bowl connected to a waste reservoir by a sewer pipe. A discharge valve is mounted on the sewer pipe to selectively allow fluid communication from the bowl to the waste reservoir. To power the toilet system, the waste reservoir is maintained under a pressure that is substantially lower than the pressure in the waste-receiving bowl, which is typically under the near-atmospheric pressure of the aircraft's passenger cabin. Thus, when the discharge valve is opened, the pressure differential between the bowl and the reservoir causes the waste in the bowl to be drawn through the pipe into the waste reservoir.
A vacuum toilet system with a discharge valve is described in U.S. Pat. No. 4,713,847. This discharge valve has a cylindrical housing that has an inner chamber sized to contain a disk-shaped gate with a hole therein. One side of the housing has an inlet aligned with an outlet located on the other side of the housing. The waste-receiving bowl is connected to the inlet of the housing by one portion of a sewer pipe and the waste reservoir is connected to the outlet of the valve housing via another portion of the sewer pipe.
A drive mechanism selectively rotates the circular gate between an open position and a closed position. In the open position, the hole in the disk-shaped gate is aligned between the inlet and the outlet to allow fluid communication for the flushing of the toilet. In the closed position, the gate blocks fluid communication between the inlet and the outlet to prevent fluid flow from the pressure differential between the bowl and the reservoir.
Applicant's assignee, MAG Aerospace Industries, Inc. has for several years sold a discharge valve having a disc shaped gate valve, known as the Monogram Sanitation Orbital Valve, Part No. 14330-050. The experience which applicant's assignee has had with this valve shows that, while it generally functions acceptably, there can be a problem associated with a scale-like deposit that builds up on the sides of its rotating disk-shaped gate and over its internal housing parts over years of exposure to the minerals and chemicals in the toilet system fluid. The scale deposit reduces the distance between the sides of the disk and the sides of the inner chamber, thereby increasing the likelihood that the disk will eventually jam inside of the housing to render the valve inoperative. Because of this scale-like deposit problem, airlines must clean or replace the gate valve before other devices in the aircraft require major servicing. Accordingly, this maintenance problem undesirably reduces the time that an aircraft is available for revenue generating operation, resulting in lost income to the airline.
Another drawback associated with the gate valve described above is that its circular disk adds extra weight to the aircraft. While other gate valves for non-aerospace applications have used valves with non-circular gates, applicant is unaware of any such valve that has a partially circular or pie-slice shaped gate for the purpose of weight reduction in an aircraft vacuum toilet system. Accordingly, applicant is not aware of any prior art reference that teaches or suggests a weight reduction due to a relatively thin, pie-slice shaped gate valve for aerospace applications.
It should therefore be appreciated that there is a need for an aircraft toilet system with a light weight gate valve that resists jamming due to scale buildup, thereby reducing maintenance costs. The present invention fulfills this need.
SUMMARY OF THE INVENTION
The present invention provides a light weight gate valve for an aircraft vacuum toilet system. The valve resists jamming due to scale buildup, thereby reducing maintenance costs associated with repair or cleaning.
The gate valve is intended for mounting between two portions of a sewer pipe connected between a waste receiving bowl and a waste reservoir. More particularly, the gate valve includes a housing having two internal sidewalls cooperatively defining an internal valve chamber with an inlet opening opposing an outlet opening. The inlet opening is connected to the portion of the sewer pipe in fluid communication with the waste receiving bowl and the outlet opening is connected to the portion of the sewer pipe in fluid communication with the waste reservoir. The sidewalls of the housing are located in opposed, parallel relation.
A gate is mounted between the interior sidewalls of the housing for rotation about a predetermined axis to selectively allow fluid communication between the inlet and outlet of the housing. The gate has opposing side surfaces, each of which opposes an associated one of the sidewalls within the housing and is in parallel relation thereto. The valve can also include an actuator, which can be, for example, a reversible electric motor or a pneumatic piston/cylinder, mounted to the housing to rotate the gate about the predetermined axis.
In the previously referred to Monogram Sanitation orbital valve, the spacing between each side of the disk and the adjacent interior wall of the housing was in the range of 0.0035 inch to 0.006 inch. The gap was determined by the clearance necessary between the housing and the face seal to ensure that the seal works well. In normal usage, with averagely hard water, mineral deposits would buildup to the level that the movement of the disk would be seriously inhibited, or stopped, in about three years. Unfortunately, this time period is less than the period of about four years at which airliners are typically taken out of service for major overhaul. The causes of the problem were not appreciated for a long time and, when they were, they were not obvious how they could be readily overcome. Applicant has taken the step of increasing the spacing between the side of the gate and each adjacent interior side wall of the housing, outside the region of the housing within the seal ring, to more than nine times the corresponding spacing in the region inside the seal ring. The spacing between the surfaces of the housing facing the gate in the region overlapped by and within the face seal remain as close as they were before. Applicant has thus created a dual level of spacing by removing more material from the internal faces of the housing opposed to the gate in the region outside the seal than lie within it. This is a step which would not be obvious due to the general desire in airline practice to hold dimensions to a minimum to satisfy weight and overall device envelope considerations. Applicant has also learned that there is an upper limit for the spacing of about 0.120 inch, beyond which the size and weight of the entire discharge valve becomes too large to be acceptable from a weight, size and cost standpoint. Thus, applicant's preferred spacing between each side of the disk valve and the adjacent interior wall of the housing in the region outside the seal, is in the range of 0.050 inch to 0.120 inches. The preferred spacing is about 0.060 inch. In the region within the seal it is still in the range of 0.0035 inch to 0.006 inch.
This separation in the region outside the seal is large enough to significantly reduce valve maintenance due to scale build-up on the sides of the gate. Thus, the operator of an aircraft utilizing the gate valve of the present invention can enjoy the cost savings associated with such reduced maintenance. Further, because the disk is less likely to jam, the toilet system is less likely to break down, thereby advantageously assuring that the full complement of lavatories on a particular aircraft are available for passenger use.
In more detailed aspects of the invention, the gate has a partial-disk shape, like a slice of pie, and also has a sharp edge along at least one edge of the periphery to cut debris. The partial-
Christie Parker & Hale LLP
Mag Aerospace Industries, Inc.
Rivell John
Schoenfeld Meredith H.
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