AU634008B2

AU634008B2 - Vacuum sewer arrangement

Info

Publication number: AU634008B2
Application number: AU68527/90A
Authority: AU
Inventors: Gunnar Lindroos
Original assignee: Wartsila Oy AB
Current assignee: Wartsila Oy AB
Priority date: 1990-01-02
Filing date: 1990-12-28
Publication date: 1993-02-11
Anticipated expiration: 2010-12-28
Also published as: FI92085C; CA2032882C; JPH0438336A; ES2062422T3; CA2032882A1; KR0148792B1; FI910027A0; FI910027A; EP0436357A1; DK0436357T5; KR910014571A; NO905623D0; NO905623L; DE69012773D1; DE69012773T2; EP0436357B1; JP3040493B2; AU6852790A; FI92085B; NO315093B1

Description

AUSTRALIA

634008 iJ T PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification Lodged: Accepted: Lapsed: Published: Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Oy V, artsila AB Address of Applicant: PB 230, SF-00101 Helsinki, Finland.

Actual Inventors: Gunnar Lindroos Address for Service: CALLINAN LAWRIE, 278 High Street, Kew, 3101, Victoria, Australia Complete Specification for the invention entitled: "VACUUM SEWER ARRANGEMENT" The following statement is a full description of this invention, including the best method of performing it known to me:- 1 VACUUM SEWER ARRANGEMENT The invention relates to a vacuum sewer arrangement for use with a waste-receiving bowl.

In a vacuum sewer arrangement, a waste-receiving toilet or WC bowl is connected to a sewer pipe by means of a sewer valve, and a vacuum is maintained in the sewer pipe. In order to carry out a flushing ooeration, the sewer valve is opened and waste in the bowl is inducted into the sewer pipe.

The waste forms a movable plug in the sewer pipe, and the pressure difference across the plug propels the plug through the sewer pipe to a waste-receiving tank. In a conventional vacuum sewer arrangement, air for transportation of the waste plug enters the sewer by way of the sewer valve. \hen the sewer valve closes, tne plug stops moving almost immediately.

Two main factors determine how long the sewer valve remains open. Firstly, che sewer valve must remain open for long enough to ensure, with a reasonable degree of certainty, that the waste in the bowl has entered the sewer pipe. Although normally the waste is Dressed into the sewer almost instantaneously, it is usual to allow about two seconds for the waste to leave the bowl. Secondly, it is imoortant for proper operation of a vacuum sewer arrangement that the chance of one waste plug merging with a preceding or succeeding plug in the sewer pipe be very small, and therefore the plug must travel a substantial distance along the sewer pipe, for example at least 10 m, before stopping. In vacuum sewer arrangements that are currently in use, the waste plug typically travels at a maximum speed of around 5 to 10 m/s. Therefore. in a typical vacuum sewer arrangement, the sewer valve remains open for about four seconds on each flush.

i- 2 The waste will enter the sewer pipe immediately the sewer valve opens, followed by a large quantity of air.

This causes considerable pressure variations in the bowl, in particular during the opening and closing phase of the sewer valve when material (waste or air) is inducted through a relatively small opening. Due to this, a high noise level is usually generated. The noise level is dependent on the pressure difference between the interior of the bowl and the sewer pipe the greater the difference, the greater the noise tends to be.

The Patent Publication GB-A-2203431 discloses a vacuum sewer arrangement with a noise-reducing air inlet device connected to the sewer immediately downstream of the sewer va i v'.

One object of the present invention is to orovide a simplified ana more reliable version of the arrangement disclosed in GB-A-2203461.

A disadvantage of the vacuum sewer arrangement described with reference to Figure 1 in GB-A-2203461 is that a vacuum accumulator may be required in crder to provide a sufficiently large volume under vacuum for proper functioning of the sewer valve and the air inlet valve. Also, since the air inlet valve opens after the sewer valve, and a single control device is used to control both the sewer valve and the air inlet valve, a throttle is required in order to delay operation of the air inlet valve relative to the sewer valve. Further, the proper location z the outlet of the air inlet duct depends on several factors, and it is not possible to be certain that these factors will remain constant or will be the same from installation to installation.

Aordin to thy invention a mp o: and me.

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In accordance with a first aspect of the present invention, therefore, there is provided a vacuum sewer arrangement including: a sewage providing unit; a sewer pipe defining an interior space; means for estabL h ing, in the interior space of the sewer pipe, a vacuum sufficient for obtaining efficient sewage transport in the sewer pipe; a nornally-closed sewer valv e connecting the sewage-providing unit to the sewer pipe; a control device for controlling operad:ion of the sewer valve to allow discharge of sewage from the sewage-providing unit to the sewer pipe; an air inlet duct "or letting air into the sewer pipe separately for the sewage-providing unit; and an air inlet valve with means operating it in response to pressure variations in the sewer pipe, for controlling the flow of air through the air inlet duct into the sewer pipe when the sewer pipe is under proper vacuum for effective sewage transport.

In accordance with a further aspect of the present invention there is provided a method of operating a vacuum sewer arrangement which includes a sewage-providing unit, a sewer pipe defining an interior space, a normally-dosed sewer valve connecting the sewage-providing unit to the sewer pipe, and an air inlet duct for letting air in to the sewer pipe separately from the sewage-providing unit, the air inlet duct being connected to the sewer pipe at a point close to the sewe. valve, said method including: establishing, in the interior space of the sewer .O pipe, a vacuum sufficient for obtaining effective sewage transport in the sewer pipe, thereafter opening the sewer valve, whereby sewage in the sewage-providing unit is inducted into the sewer pipe to form a movable plug therein, immediately after the sewage plug has passed the point where the air inlet duct is connected to the sewer pipe introducing air into the sewer pipe by way of the air inlet duct, closing the sewer valve, and discontinuing introduction of air into the sewer pipe by way of the air inlet duct when the sewage plug has travelled the full length of the sewer pipe or a distance of at least 10 m from the sewer valve.

the ai inlet valv-in -regpons ee- he -prccpur -i1-he vacuum sewer close to th y-s--ve, as stated in claim The air inlet duct can be sound insulated to the point where air flowing through the air inlet duct will not cause a disturbing level of noise. The noise level of a vacuum toilet sewer arrangement according to the invention can be further reduced by providing, as known per se, the bowl with a lid forming a substantially airtight and sound-proof closure at the top of the bowl. In this case, it is favourable that the lid be of relatively thick soundinsulating material. Various plastics materials, and in particular sandwich structures, are well suited for this purpose. If the lid provides a seal, the volume of air contained in the bowl may be too small for proper discharge of the sewage from the bowl, ,n which case additional air san be provided through a separate tube. This tube may have its inlet end connected to the air inlet duct upstream of the air inlet valve, but it may also be a completely separate tube. The lowest noise level is achieved if the tube is provided with a muffler, is sound insulated and has its inlet end outside the toilet compartment. The tube is preferably provided with a non-return valve in order to prevent escape cf odours from the toilet bowl into the surroundings.

The connection of the air inlet duct to the sewer is il desirably sufficiently close to the sewer valve that ir normal operation of the vacuum sewer arrangement, the sewer plug formed when the waste enters the sewer through the sewer valve, will pass the outlet of the air inlet duct less than one second after the sewer valve reaches its fully open condition, and preferably less than 0.5 seconds after the sewer valve reaches its fully open condition.

Conveniently the air inlet valve opens less than seconds after the sewer valve opens, preferably between 1 and 2 seconds after the sewer valve opens, and most prefer- L_ ably about 1.5 seconds after the sewer valve opens.

However, the time at which the air inlet valve opens should be selected relative to the distance between the sewer valve and the outlet of the air inlet duct and the expected speed of travel of the sewage plug so that the air inlet valve will not open before the sewage plug has passed the air inlet duct, since otherwise proper transportation of the plug might not be achieved. The air inlet valve will typically stay open for about 5 seconds or less. This introduces slightly more transport air into the sewer than is usual in conventional vacuum sewer systems. The increased amount of air provides a greater travel distance for a sewage plug discharged from the bowl.

Conventionally, the sewer valve of a vacuum sewer arrangement is operated by using the vacuum present in the vacuum sewer. In an arrangement according to the invention the same vacuum can be used also for operating the air inlet valve. This gives a simple and reliable structure.

A check valve should be arranged between the sewer valve control device and the sewer, so that a pressure rise in the sewer is unable to have any influence on the pressure in the valve control device.

In the descriptive portion of this specifiuation and in the claims the term "vacuum" should be taken to mean a sub-atmospheric pressure of a magnitude suitable for use in a vacuum sewer system. Conventionally, the pressure in such a system is about 38 cm Hg. The term "atmospheric" as used herein means ambient pressure and thus, in the case of an aircraft in flight can mean the cabin pressure.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 schematically shows, partly at an enlarged scale, one embodiment of the invention, and Figure 2 shows schematically an arrangement according to the invention having multiple waste-receiving bowls.

Figure 1 illustrates a waste-receiving bowl 1 and a sewer pipe 2 connected to the bowl 1 by a sewer valve assembly 3. The interior space of the sewer pipe 2 is maintained under vacuum, which may be provided as .,nown per se, by a vacuum pump (not shcwn). Such a pump is usually connected to the downstream end of the sewer pipe 2, or may be connected tc a sewage collecting tank (not shown) into whic', the pipe discharges. The sewer valve assembly 3 includes a sewer valve proper and a sewer valve operating device which opens the sewer valve by using the vacuum). Various valve assemblies of this type are described in US-A-3,482,267, 3,807,431, 3,984,080 and 4,376,444.

An air inlet duct 4 opens into the sewer pipe 2 through an outlet 36. An air inlet valve assembly 6 is connected to the air inlet duct 4.

A control device 7, which controls the valve assembly 3, is activated by a function impulse 8. Such an impulse may originate from a push button operated by the user of the toilet and may be transmitted, for instance mechanically, in the form of a pressure impulse, or electrically in i 25 the form of a signal pulse, to the control device 7. The I function impulse 8 may be dependent on, for instance the closing of a lid 17 of the toilet bowl or on other factcrs which are relevant to controlling the flushing cf the toilet. Since these factors also are well known in the art, neither the creating of a function impulse nor the manner of operation of the control device 7 will be explained here.

A general principle behind the operation of a vacuum _1 I sewer arrangement is that the sewer valve should open only when there is sufficient vacuum in the sewer pipe for effective transport of sewage. In order to achieve this, the vacuum required to open the sewer valve is taken from the sewer pipe 2 or from another point of the vacuum system. If the available vacuum is too weak for effective transp., t of sewage, the sewer valve will not open. in the emboimrent of Figure 1 the vacuum required for the operation of the sewer valve is communicated from the sewer pipe 2 to the control device 7 through a tube 9 and a check valve 10. Upon receiving function impulse 8, the control device 7 transmits vacuum received from the sewer pipe 2 via a tube 13 to the operating device of the sewer val.e assembly, which then opens the sewer valve. At the same time the control device 7 transmits vacuum through a tube 34 towards the air inlet valve assembly 6.

The distance of the outlet 36 of the air inlet duct 4 from the sewer valve assembly 3 and the delay between opening of the sewer valve and opening of the air inlet valve are selected so that, in normal operation, the air inlet duct 4 supplies air to the sewer nractically immediately after the plug of sewage from the bowl 1 has passed the outlet 36. Since air for transporting the plug is then provided through the air inlet duct, the sewer valve need not be held open any longer than is necessary to ensure that the plug has passed the outlet 36. When the sewer valve closes, air is no longer inducted through the toilet bowl and the noise level therein is reduced.

Moreover, when both the sewer valve and the air inlet valve are open, a'ir is inducted through the sewer valve at a lower rate and the noise level is also reduced.

The basic structure of an arrangement according to the invention requires that air is led through the air inlet duct 4 to the vacuum sewer pipe 2 when the sewage-providing unit 1 is emptied. This substantially reduces the noise level, but nevertheless, the noise level might be unpleasantly high. Hence, letting in air by way of an air inlet duct is not always sufficient to reduce the noise level to an acceptable value. Additional measures might be necessary for improving the technical effect of the basic embodiment of the invention. A suitable additional measure is to provide the bowl 1 or a corresponding sewage-providing unit with an airtight lid 17. Such a lid desirably should be made relatively sound-proof. Opening of the sewer valve can, as known per se, easily be made dependent on the closing of the lid 17, so that the valve opens only when the lid is closed.

Using an airtight lid in a vacuum toilet may result in the amount of air present in the bowl 1 being too small for efficient flushing of the bowl, flushing being effected by discharging a volume of water into the bowl to assist in removing the waste plug from the bowl. The water supply are not shown in either of Figures 1 or 2. If too little air is available in the bowl with the lid 17 closed, the problem can be overcome by connecting an air tube 18 to the bowl 1. Air is led into the bowl througn the tube 18 and a check valve 19 without any substantial noise. The air supply for the tube 18 can be taken from any place, fcr instance, from outside the toilet compartment and can, for example, be passed through an air silencer or the like incorporated in the valve 19.

In the embodiment shown in Figure 1, the air inlet valve 6 and the air inlet duct 4 are surrounded by a tube of sound insulating material. This tube forms a noise damping air entrance duct coaxially disposed around the duct 4 to leave an annular air passage between the tube and the duct 4. Ambient air flows into this passage via an entrance at the lower end of the tube 20 as is siown by arrows 15. The air inlet valve 6 comprises a diaphragm a rubber pad) that is deflectable towards and away from The upper end of the duct 4, depending on the difference in pressure between the duct 4 and a control

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8 chamber 32, which is connected to the narrow-bore tube 34 leading back to the tu'ne 13. The control chamber 32 is bounded partially by the diaphragm 30 and partially by a rigid wall 38, to which the diaphragm 30 is connected through a flexible rubber skirt 42 and a flange 44. The flexible rubber skirt 42 biases the diaphragm 30 towards the upper end of the duct 4.

Normally, the pressure in tube 13 is substantially that existing in the toilet compartment normal atmospheric pressure or cabin-pressure in an aircraft) while there is a lower pressure in the duct 4 because it is directly connected to the sewer pipe 2, which is under vacuum. As a result, the diaphragm 30 is held in firm sealing contact with the upper end of the duct 4. Cn receiving a function impulse 8, the control unit 7 communicates vacuum from the sewer pipe 2 to the tube 13. This opens the sewer valve, and waste in the bowl 1 is drawn rapidly into the sewer pipe 2.

The vacuum in the tube 13 is communicated through the tube 34 to the control chamber 32 and the pressures on the two sides of the diaphragm then move towards equality.

However, owing to the bias provided by the resilient skirt 42, and the difference between the area of the diaphragm exposed to pressure in the duct 4 and the area of the diaphragm and skirt effectively exposed to pressure ir, the chamber 32, the diaphragm 30 remains in contact with the duct 4 and therefore the air inlet valve remains close, When the waste passes the outlet 36 of the duct 4, and is followed by air from the bowl 1, the pressure in the sewer pipe 2 and consequently also in the duct 4 rises, but the check valve 10 prevents a corresponding rise in pressure in the tube 34. Then, the diaphragm 30 can become unseated from the upper end of the duct 4, and air can enter the sewer pipe 2 through the duct 4. At about the same time as the air inlet valve opens, the control unit 7 starts to communicate atmospheric pressure to the tube 13, causing i 9 the sewer valve to close. Atmospheric pressure is then also commun-icated to the control chamber 32, with a slight delay due to the length of the tube 34, and the air inlet valve 6 closes.

The toilet lid 17 is in sealing relationship with the rim of the bowl 1, and the function impulse 8 can only be generated when the lid 17 is closed. When the sewer valve opens and waste is drawn into the sewer pipe 2, air for transporting the waste is inducted into the bowl 1 through the tube 18 and the check valve 19 and th- pressure in the sewer pipe 2 behind the waste remains close to atmospheric.

The outlet 36 of duct 4 is sufficiently close to the sewer valve assembly 3 that the operation of the sewer valve directly induces operation of the air inlet valve 6.

Thus, when the sewer valve opens, is the rise in pressure in the sewer pipe when the waste plug from the toilet bowl has passed the outlet 36 that causes the air inlet valve to open, and when the sewer val e closes in response to control unit 7, the fall in pressure (increased vacuum) in the sewer pipe causes the air inlet valve 6 to close.

Since the air inlet valve cannot open until the plug of waste has passed the outlet 36, there is no possibility of the air inlet valve opening too soon and interfering with reliable transportation of waste from the bowl 1 into the sewer pipe 2.

Pigure 2 illustrates schematically an arrangement in which the sewer pipe 2 has several branches 48 connected to respective waste-receiving bowls 1 through respective sewer valves 3. An air inlet valve 50 and a control unit 7 are associated with each toilet bowl 1 and sewer valve 3. The arrangement of each bowl 1, sewer valve, control unit and air inlet valve may be as shown in Fig-re 1.

The air inlet valves 50 operate independently of one another, so that, for example, application of a function impulse to the control unit 7 associated with one of the air inlet valves has no effect on the other air inlet valve(s).

It will be appreciated that the invention is not restricted to the particular embodiments that have been described, and that variations may be made therein without departing from the scope of the invention as defined in the following claims.

Claims

1. A vacuum sewer arrangement including: a sewage providing unit; a sewer pipe defining an interior space; means for establishing, in the interior space of the sewer pipe, a vacuum sufficient for obtaining efficient sewage transport in the sewer pipe; a normally- dosed sewer valve connecting the sewage-providing unit to the sewer pipe; a control device for controlling operation of the sewer valve to allow discharge of sewage from the sewage-providing unit to the sewer pipe; an air inlet duct for letting air into the sewer pipe separately for the sewage-providing unit; and an air inlet valve with means operating it in response to pressure variations in the sewer pipe, for controlling the flow of air through the air inlet duct into the sewer pipe when the sewer pipe is under proper vacuum for effective sewage transport.

2. The arrangement according to claim 1, wherein the air inlet duct is connected to the sewer pipe at a point dose to and downstream of the sewer valve.

3. The arrangement according to claim 1 or claim 2, wherein the air inlet valve includes an annular seat portion defining an opening that is in open communication with the air inlet duct, a ,-ealing member separating the opening from the influence of ambient air, the sealing member being displaceable between a position in which it engages the seat portion and a position in which it is spaced from the seat portion, and means for controlling the position of the sealing member.

4. The arrangement according to claim 3, wherein the means for controlling the position of the sealing member include flexible wall means dc_6-ning a control chamber bounded by the sealing member, and means for controlling the pressure in the control chamber. 12 The arrangement according to claim 4, wherein the control device includes means for communicating vacuum to both the sewer valve operating device and the control chamber of the air inlet 'lve.

6. The arrangement according to any one of the preceding claims, wherein the sewage-providing unit is a wc-bowl having a lid that provides a substantially airtight closure thereto.

7. The arrangement according to claim 6, wherein the bowl is provided with a tube for delivering air to the interior of the bowl when the lid of the bowl is closed.

8. The arrangement according to claim 7, wherein the tube for delivering air to the bowl is provided with a check valve.

9. A vacuum sewer arrangement according to any one of the preceding claims, including a plurality of sewer branches each defining an interior space in open communication with the interior space of the sewer pipe, a plurality of normally-closed sewer valves connected between respective sewage-providing units and respective sewer branches, control means for controlling operation of the sewer valves, a plurality of air inlet ducts for lettig air into the sewer branches respectively, separately from the sewage-providing units, the air in'et ducts being connected to the respective sewer branches close to the respect sewer valves, and a plurality of air inlet valves one associated with each sewer valve respectively, for controlling separately the flow of air through any of the air inlet ducts into the associated sewer branch in response to the function of the associated sewer valve. A method of operating a vacuum sewer arrangement which includes a sewage-providing unit, a sewer pipe defining an interior space, a normally- dosed sewer valve connecting the sewage-providing unit to the sewer pipe, and an air inlet duct for letting air in to the sewer pipe separately from the sewage- providing unit, the air inlet duct b;ing connected to the sewer pipe at a point 13 close to the sewer valve, said method including: establishing, in the interior space of the sewer pipe, a vacuum sufficient for obtaining effective sewage transport in the sewer pipe, thereafter opening the sewer valve, whereby sewage in the sewage-providing unit is inducted into the sewer pipe: to form a movable plug therein, immediately after the sewage plug has passed the point where the air inlet duct is connected to the sewer pipe introducing air into the sewer pipe by way of the air inlet duct, closing the sewer valve, and discontinuing introduction of air into the sewer pipe by way of the air inlet duct when the sewage plug has travelled the full length of the sewer pipe or a distance of at least 10 m from the sewer valve.

11. A vacuum sewer arrangement, substantially as herein described with reference to the accompan} ,tg drawings.

12. A method of operating a vacuum sewer arrangement, substantially as herein described with reference to the accompanying drawings. D A T E D this 28th day of December, 1990. Oy Wartsila AB By its Patent Attorneys: CALLINAN LAWRIE 4J/