Baths – closets – sinks – and spittoons – Flush closet – Bowl
Reexamination Certificate
1999-06-30
2001-06-12
Walczak, David J. (Department: 3751)
Baths, closets, sinks, and spittoons
Flush closet
Bowl
C004S434000
Reexamination Certificate
active
06243887
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a sewer system.
There are three basic types of known sewer systems. The most frequently used is the conventional gravitation sewer system having sewer pipes inclined downwards, in which the waste water flows by gravitation. In the pressure sewer system overpressure is used for transporting waste water through small-bore sewer pipes. The pressure system is not widely used, although it provides advantages such as small pipe dimensions and the possibility to lay pipes extending upward. In the vacuum sewer system, the pressure in the sewer pipe is reduced to about one half of atmospheric pressure and the pressure difference between the atmosphere and the reduced pressure in the sewer pipe is used for the transportation of sewage. The vacuum sewer system has achieved wide use in ships, aircraft and trains. In principal, it has the same advantages as the pressure sewer system. The main disadvantages of the vacuum sewer system are a relatively high cost and the fact that the sanitary units connected to the sewer must be separated from the sewer system by a normally closed discharge valve, which may cause flooding problems.
A fourth type of known sewer system is the low vacuum sewer system. The low vacuum sewer system is technically between the gravitation sewer system and the vacuum sewer system. In the case of the low vacuum sewer system, the toilet bowl may be connected to the sewer pipe through a trap, as in a gravity sewer system, or through a normally-closed discharge valve, as in the normal vacuum sewer system. For emptying a toilet bowl of a low vacuum system, a relatively low vacuum (about 0.1 to 0.4 bar below atmospheric) is generated in the sewer pipe. In some known systems of this type, a sluice device has been used as an interface between the space that is under vacuum, such as the sewer pipe, and a collecting container under atmospheric pressure. Such sluice devices have poor operational reliability because of leakage caused by deposits on the sealing surfaces of the sluice. Patent Publication SE 358196 describes a low vacuum system where the generation of vacuum requires a check valve in the sewer pipe. Practice has shown that such a check valve will not function satisfactorily in the long run. Furthermore, it is difficult to avoid dirt being drawn into the ducts that lead from the sewer pipe to the vacuum generator and which should normally contain only air. These difficulties seem to have been detrimental for marketing devices according to Patent Publication SE 358196. In general, known systems of this kind have had such a primitive or crude design that their operational reliability has suffered. They have been marketed substantially only as individual toilet units for summer cottages or the like.
SUMMARY OF THE INVENTION
The object of the invention is to develop a sewer system for buildings with several sanitary units, such as toilet bowls and urinals, in particular multi-family buildings such as apartment buildings, and hotels, hospitals or the like. The aim is to provide a simple and operationally reliable sewer system that neither requires the expensive technical solutions typical for vacuum sewer systems nor requires conventional sewer piping with large diameter downward sloping sewer pipes. On the contrary, the sewer pipes should have a small bore and it should be possible to have substantial distances laid horizontally and even to have some short sections laid upward.
Another object of the invention is to reduce the water consumption of the sanitary units to such an extent that it becomes economically profitable to separate the sanitary sewers containing so-called black water from other waste water sewers containing so-called gray water and subject the toilet waste to biological treatment. This requires that the amount of water at each toilet flush should not exceed 2 liters, preferably should not exceed 1 liter. Thereby the solids content of the toilet waste will be high, which makes it economically feasible to treat the toilet waste separately from other waste water.
A third object of the invention is to obtain an operationally reliable low cost suction system for emptying sanitary units, in which waste liquid drawn from a sanitary unit may freely flow from the vacuum area to an area under atmospheric pressure without passing check valves or other flow obstructing means.
A fourth object is that it should be easy to install a system according to the invention as a replacement for the normal gravitation sewer system in an existing building, or instead of a gravitation system during construction of a new building, whereby the discharge end of the building's internal sewer system should be directly connectable to the external sewer serving the building or to a special sewer network for toilet waste.
It is important for the application of the invention that each toilet bowl (or other sanitary unit) should have its own separate branch sewer pipe and its own separate vacuum generator. Vacuum (reduced pressure) is generated only intermittently, i.e. separately for each desired emptying of a sanitary unit. The vacuum generator, i.e. the device that generates vacuum, must allow free flow of the waste from the vacuum section of the sewer system to a section under atmospheric pressure. Suitable designs for this purpose are described below. The branch sewer pipes of each sanitary unit may be joined to a common pipe downstream of the vacuum generator of the sanitary unit.
For practical use it is important that smaller amounts of liquid may flow out from a toilet bowl without starting the normal emptying cycle based on vacuum generation. Thus, one should be able to empty a glass of water into a toilet bowl without any special measures.
Since vacuum is generated separately for each emptying operation, it is important that the volume within which the pressure has to be lowered is not too large. On the other hand, a certain minimum vacuum volume is needed in order to achieve a sufficient vacuum capacity to ensure a reliable emptying function. For providing a suitable volume it is recommended that the length of the sewer pipe between the trap and the device for generating vacuum is 2 to 50 m, preferably 5 to 15 m. Toilet emptying through suction requires relatively small-bore sewer pipes. The inner diameter of the length of sewer pipe between the outlet of the toilet bowl and the device for generating vacuum should therefore advantageously be at the most 65 mm, preferably at the most 55 mm.
An air driven ejector, preferably a so-called on-line ejector integral with the sewer pipe, has shown itself to be suitable in a system according to the invention. The working medium of such an ejector is advantageously supplied in the form of pressurized air or other pressurized gas. For achieving a sufficiently rapid vacuum generation in the case of the working medium being pressurized gas, the ejector should preferably be supplied with working medium for some seconds with a flow rate of 700 to 2000 l/min, preferably 1000 to 1500 l/min. The unit l/min relates to a volume that is calculated at a temperature of 20° C. and atmospheric pressure. The dynamic pressure in the supply of working medium to the ejector is advantageously 7 to 40 kPa, preferably 10 to 30 kPa.
An on-line ejector of the type referred to is useful because toilet waste can easily pass through the ejector. An ejector of a suitable type is described in U.S. Pat. No. 5,813,061, the disclosure of which is hereby incorporated by reference herein. This ejector is intended for generating a considerably stronger vacuum (lower absolute pressure) than is needed in a system according to the invention, but a modification of the performance of the ejector can be made by reducing the flow of working medium. The best operational reliability is usually obtained by connecting the ejector at an angle to the sewer pipe, so that the segments of the sewer pipe immediately before and after the ejector form an angle of at least 120°, preferably at least 135°.
For the same reasons as des
Nilsson Åke
Ohlsson Bengt
Palffy Björn von Varfalva
Evac International Oy
Huynh Khoa D.
Smith-Hill John
Smith-Hill and Bedell
Walczak David J.
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