Baths – closets – sinks – and spittoons – Flush closet – Bowl
Reexamination Certificate
2002-08-30
2004-01-27
Bennett, Henry (Department: 3751)
Baths, closets, sinks, and spittoons
Flush closet
Bowl
C004S321000, C004S2090FF, C055S522000
Reexamination Certificate
active
06681412
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 102 04 248.9, filed on Feb. 2, 2002, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a filter arrangement for a vacuum toilet system including at least one filter element for removing liquid and solid contaminants from a volume flow of air, whereby the filter element is arranged in a filter housing that is connected to the top of the waste water tank of the vacuum toilet system.
BACKGROUND INFORMATION
Commercial aircraft for passenger transport are typically equipped with a vacuum toilet system, which includes a waste water tank and at least one toilet and/or other waste disposal receptacles connected to the waste water tank by a waste collection line, and which uses a vacuum suction effect to suck the waste materials that are to be conveyed from the toilet into the waste water tank. This waste material stream or flow is a mixture of cabin air and waste water that comprises the toilet flush water, liquid and solid human waste, and other materials such as toilet paper, tissues, and other wastes that a passenger might dispose of into the toilet. The suction effect is typically created by the pressure difference between the low outside ambient air pressure and the higher interior pressure within the aircraft cabin during flight at typical cruise altitudes. Another possibility for generating the vacuum or suction effect is through the use of a conventional vacuum generator, for example when the aircraft is on the ground or at a low flight altitude which would provide an inadequate pressure differential.
The vacuum toilet system is connected via the waste water tank and through an outlet or exhaust air line to the external environment outside the aircraft. In other words, the outlet or exhaust line is connected from the waste water tank, for example through the vacuum generator or the like, to an overboard exhaust air outlet. The flow of cabin air and waste water is conveyed from the toilets through the collection line into the waste water tank, where the waste water is collected in the tank by the effect of gravity, while the airflow is conveyed out of the tank through the exhaust airline. However, this airflow leaving the waste water tank can still be contaminated with some liquid and solid wastes, for example due to the vigorous intermingling of the air with the solid and liquid wastes during the vacuum transport through the waste collection line. In order to separate and isolate the waste-contaminated portion of the toilet system from the outside exhaust air, and from the devices needed for generating the vacuum pressure differential, it is therefore necessary to provide a filter system for the exhaust air as it leaves the tank.
At present, the conventional filter systems installed in aircraft toilet systems are all embodied as volume, bulk, or storage filters. In other words, the present conventional filter systems all achieve the required filtration in the body volume or bulk of a filter medium. A conventional so-called waste separator comprising such a filter is typically arranged between the waste water tank and the exhaust air line. The contaminated airflow exiting from the waste water tank or the waste collection line is filtered and thereby decontaminated through the waste separator, and the output filtered airflow is then directed through the exhaust air line to the outside environment. Thereby, it is intended that any remaining solid or liquid waste contaminants are filtered out and removed from the airflow by the waste separator.
In the typical conventional arrangement of such a waste separator
100
, e.g. as shown in present
FIG. 1
, a first filter element
102
consisting of a crimped or random-looped Perlon thread is arranged in a housing
101
including a bottom baffle
101
A. This first filter element
102
separates any remaining contaminants, and especially liquid contaminant residues, from the unfiltered contaminant-laden airflow
2
, which flows around and then up over the baffle
101
A and into the bottom of the filter
102
. The separated liquid runs down by the effect of gravity and drains through a small opening
103
in the bottom of the housing
101
, i.e. in the bottom of the baffle
101
A, back into the waste water tank. Since the conveyed airflow
2
can also be contaminated with small solid contaminant particles of toilet paper, tissues, newspaper, other waste paper, or other similar solid waste materials, such solid particles can be sucked against the bottom inlet surface of the filter element
102
, or can be sucked into the bulk volume of the filter element
102
, or can become lodged and thus plugged-up in the drain opening
103
of the housing
101
.
The conventional arrangement of the waste separator
100
further includes a second filter element
104
, consisting of a wound or rolled steel wire braid or mesh, arranged above the first filter element
102
. After emerging from the top of the first filter
102
, the partially filtered airflow is directed radially outwardly by another baffle
101
B and then passes upwardly through the second filter element
104
, where it is further cleaned or separated from contaminants. The final resulting filtered airflow
3
is then directed out of the exhaust air line
105
.
The conventional filter system described above suffers the substantial disadvantage that it can become clogged, plugged or saturated with waste materials, and especially solid particle waste materials. Namely, as described above, solid waste materials such as paper particles and the like can become sucked onto the surface or into the body or volume of the crimped or crinkled fiber material of the first filter. Over time, the solid waste particles accumulate on the surface and in the body of the filter and begin to plug it up. Any solid waste particles that manage to get through the first filter can then become adhered on and plug the second filter consisting of a steel wire mesh or braid. This plugging of the filter system, which worsens over time, progressively increases the airflow resistance and thus decreases the flow of air through the filter arrangement.
After substantial saturation of the filter has occurred, it becomes impossible to establish a system differential pressure between the toilet and the waste water tank of sufficient strength to reliably convey the waste flow, due to the substantial pressure drop across the filter arrangement. As a result, there is the danger of blockage or plugging of the waste water collection line, which can ultimately lead to the failure of the entire toilet system. Since the conventional filter system cannot be cleaned during use, i.e. during the time it is installed in the toilet system, this progressive plugging or saturation of the filter arrangement cannot be corrected except for carrying out a substantial maintenance procedure of removing and replacing the filter arrangement, which involves substantial cost, effort and downtime of the aircraft.
Another problem is that some small waste particles, both solid and liquid, can permeate entirely through both filter stages, and thus be sucked into the exhaust air outlet line. There, the remaining waste particles will contaminate the mechanical components of the vacuum generator, which could lead to a malfunction or breakdown thereof, or are transported to the overboard outlet where the waste soils the outer skin of the aircraft fuselage.
A further disadvantage, as briefly mentioned above, is that the cleaning or maintenance of the filter system in conventional arrangements requires a substantial effort and expense. The waste water tank(s) with the conventional waste separator arranged thereon is(are) typically installed in the rear tail region behind the rearmost freight or cargo compartment in an aircraft, for example in an Airbus A
340
aircraft. It is difficult to access the filter elements that must be cleaned or exchanged, and therefore it becomes necessary
Doss Martin
Erdmann Wolfgang
Ohlfest Carsten
Airbus Deutschland GmbH
Bennett Henry
Fasse W. F.
Fasse W. G.
Kokabi Azadeh
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