Vacuum toilet system

Abstract: A vacuum toilet system for a vehicle (e.g. an air­ craft) uses grey water from a wash basin (40) to rinse a toilet bowl (2) during flushing of the latter. The grey water is collected in a reservoir (338) and can be drawn into the bowl (2) by the vacuum in the sewer pipe (8) to which the bowl (2) is connected. Air can enter the bowl (via 352) to combine with the rinse water during flushing.

Description: This invention relates to a vacuum toilet system for use in a transport vehicle. Vacuum toilet systems have been known for many years. The modern vacuum toilet system comprises a waste-receiving bowl, a sewer pipe that can be placed under a pressure that is substantially lower than that in the interior of the waste-receiving bowl, and a discharge valve for controlling passage of material from the waste-receiving bowl into the sewer pipe. A rinse liquid outlet is provided near the rim of the waste-receiving bowl and is connected through a rinse liquid valve to a source of pressurized rinse liquid. During a flush cycle, in which the discharge valve is opened, the rinse liquid valve is opened and rinse liquid is introduced into the waste-receiving bowl. Non-recirculating vacuum toilet systems using plain water as a rinse liquid are attractive for use in aircraft. In such a system, it is conventional for the rinse liquid to be provided from the aircraft's potable water system. The potable water system includes a tank, pipes connecting the tank to consuming devices, such as the vacuum toilets and hand basins, and a pump for maintaining the water in the pipes under pressure. An aircraft toilet system comprises a holding tank for receiving waste material from the waste-receiving bowl. In order to avoid transporting material that could be discharged from the aircraft in flight, grey water, i.e. water that, though not potable, can be discharged into the environment without treatment, e.g. water from hand basins and from galley sinks, is not fed into the vacuum toilet system so that it enters the holding tank but is discharged from the aircraft through a drain mast. US-A-4713847 discloses a vacuum toilet system in which a pump is used to deliver rinse water to a toilet bowl under control of a valve that is opened in response to actuation of a flush switch. FR-A-2286922 discloses a water supply and waste disposal system for a transport vehicle in which vacuum in a sewer pipe is used to draw waste material from a waste-receiving bowl of the system. The system includes water utilization units and a reservoir for collecting grey water from these units. A rinse water pump actuated by closing a cover of the bowl is used for passing collected grey water to the waste-receiving bowl to rinse the same. Throughout this description and claims references will be made to "above" and "below", "upper" and "lower", "top" and "bottom" and it should be understood these are intended to refer to relative dispositions when the vehicle is travelling horizontally (e.g. an aircraft is in level flight). The use of these and similar terms denoting relative positions is adopted for convenience in describing the systems and should not be interpreted as restricting the invention to use when the vehicle is horizontal. What constitutes the invention is defined in the following claims 1, 5 and 9, the preambles of which acknowledge the disclosure of FR-A-2286922. In accordance with the invention, the lower pressure created in the bowl when the cover is in the closed position and the discharge valve is open is used to draw grey water into the bowl to rinse the latter. The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a part sectional schematic view of a vacuum toilet system in accordance with the present invention, and Figure 2 is a sectional view taken on the line VI-VI of Figure 1. The vacuum toilet system illustrated in Figure 1 is designed to be installed in a pressurized aircraft and comprises a toilet bowl 2 which defines an interior space for receiving waste material and has an outlet opening 4. The outlet opening is connected to one side of an electrically driven discharge valve 6, and the opposite side of the discharge valve is connected through a sewer pipe 8 to a holding tank (not shown). The discharge valve 6 controls flow of material from the toilet bowl to the holding tank. A pressure difference of about 250 mbar is required to operate the system illustrated in Figure 1. Sufficient pressure difference for operating the system exists between the cabin of the aircraft and the ambient atmosphere when the aircraft is at an altitude greater than about 5,000 m. If there is insufficient pressure difference between the cabin of the aircraft and the ambient atmosphere, a blower (not shown) is used to establish a sufficient pressure difference. Reference may be made to US-A-4713847 for further information regarding the manner in which material is transported to the tank and removed from the tank. The vacuum toilet system also comprises a hand basin 40 having a cold water valve 42, and an outlet pipe 44. The cold water valve 42 is connected through a pipe to a source (not shown) of water under pressure. The cold water valve 42 is solenoid-operated and automatically closing. When a user presses a button (not shown), a switch is closed to supply electrical current to a solenoid, which opens the valve 42. When the supply of current is discontinued, e.g. by removing pressure from the button holding the switch closed, the valve 42 recloses. The outlet pipe 44 of the hand basin 40 is connected to a grey water reservoir 338. The grey water reservoir comprises a lower housing 342 and an upper housing 340. A flush control unit 180 receives inputs from a flush initiation switch 182, which is controlled by a flush control button (not shown), and provides outputs to control the states of the discharge valve 6 and water valve 42. The flush control unit 180 may also receive other inputs and provide other outputs but these are not germane to the present invention and will not be discussed. When the flush control button is pressed, the switch 182 is closed and the unit 180 responds by initiating a flush cycle. During the flush cycle, the unit 180 opens and closes the discharge valve 6, to remove waste material from the bowl 2, and causes rinse water to be supplied to the bowl 2. The unit 180 ensures that a sufficient degree of vacuum exists in the holding tank, but the manner in which this is achieved is not pertinent to the invention and will not be described herein. Reference may be made to US-A-4713867. The present invention is concerned with the means whereby the rinse water is supplied. The vacuum toilet system illustrated allows use of grey water for rinsing the water-receiving bowl 2, and thus reduces the amount of water that needs to be carried by an aircraft equipped with a non-circulating vacuum toilet system. The system does not require that all grey water be used for toilet rinsing. The waste-receiving bowl 2 is mounted in an external shroud 300 which is spaced from the bowl. An air supply member 302 made of moulded synthetic polymer material is secured to the rim of the bowl 2 and bridges the space between the bowl 2 and the shroud 300. The member 302 is generally annular and includes a flange 304 which extends downwardly into the bowl in spaced relationship from the interior surface thereof. Accordingly, an annular channel 306 is defined between the flange 304 and the interior surface of the bowl 2. Inside the bowl 2 is a rinse water distribution pipe 320 which extends about two-thirds of the way around the bowl. The pipe opens into the annular channel 306 by way of three ports 324, one at each end of the pipe 320 and one intermediate its ends. A deflector plate (not shown) is positioned in front of each port 324. In a modification of the system shown in Figures 5 and 6, the rinse water distribution pipe 320 might extend about three-quarters of the way around the bowl 2 and have four outlet ports spaced approximately equally around the bowl 2. The rinse water distribution pipe 320 is connected by a rinse water supply pipe 328 to the reservoir 338, which receives grey water from the hand basin 40. The reservoir 338 is preferably placed close to the bowl 2, in order to minimize the length of the pipe 328. However, it might alternatively be placed directly below the hand basin 40 like an enlarged water trap. The upper and lower compartments 340, 342 of the reservoir 338 are separated by a wall 344 formed with a hole 346 for liquid flow. The rinse water supply pipe 328 extends almost to the bottom of the lower compartment 342, and is formed with a small vent hole 350 just below the top of the upper compartment 340. The drain pipe 44 is configured so that it drains easily into the reservoir 338. The overflow 88 is placed close to the reservoir 338 to minimize the amount of water stored in the pipe 44 when the reservoir is filled up to the level of the overflow. The drain pipe 44 opens into the lower compartment 342, and when the lower compartment is full, additional grey water delivered into the lower compartment enters the upper compartment through the hole 346. When full, the lower compartment 342 contains enough water for one flush of the bowl 2, for example about 200 ml. The aircraft cabin pressure is communicated to the lower compartment 342 by the drain pipe 44 and by the rinse water supply pipe 328, the vent hole 350 and the hole 346. The air supply member 302 is formed with numerous bores 352 which extend into the channel 306. The bores 352 are spaced apart around the member 302. In a practical implementation of the invention, there may be eighty such bores 352. For clarity of illustration, the bores 352 are shown in Figure 5 as extending radially, but in fact the bores are inclined at an angle of about 5 to 10° from the radial direction and all extend into the channel 306 in the counterclockwise direction with respect to the member 302, when viewed in plan. At its upper surface, the air supply member 302 is formed with grooves 358. The grooves 358 extend semi-tangentially with respect to the member 302 and are all directed inwardly in the counterclockwise direction when viewed from above. Of course, the bores 352 and grooves 358 may be directed clockwise instead of counterclockwise into the toilet bowl 2. The bowl 2 is provided with a seat 360 and a cover 362. The seat and the cover are mounted to the air supply member 302 by a hinge 364. When the seat 360 is lowered, it engages the air supply member 302 and closes the grooves 358 at the top. The seat 360 is formed with a gap 366 at the front of the toilet bowl. The cover 362 is shaped so that when it is lowered, the aircraft cabin is not in direct open communication with the interior of the toilet bowl through the gap 366. The purpose of the gap 366 is to provide a rapid flow of air into the toilet bowl, and thereby prevent build-up of underpressure therein, in the event of a malfunction that causes the valve 6 to open when the toilet is in use. The cover 362 operates the flush initiation switch 182, which is shown only schematically in Figure 1 The switch 182 is closed automatically when the cover is closed, and remains open when the cover is open. When the cover 362 is lowered, the flush control unit 180 issues a flush signal in response to the closing of the switch 182, and the discharge valve 6 is opened. Suction is applied to the interior space of the bowl 2, and this suction ensures that the cover is held down in firm, sealing relationship against the seat. Due to the partial vacuum established in the interior space of the bowl 2, air is drawn into the interior space of the bowl through the grooves 358 and the bores 352. The air that enters the annular channel 306 through the bores 352 has a substantial peripheral component of velocity and therefore executes a swirling motion about the interior space of the bowl. The air entering the toilet bowl through the grooves 358 executes a similar swirling motion. When partial vacuum is established in the toilet bowl, suction is applied through the ports 324 and the water distribution pipe 320 to the water supply pipe 328. Water is drawn into the pipe 328 from the lower compartment 342 and is discharged into the channel 306 through the ports 324. The water leaving the pipe 320 through the ports 324 impinges on the deflector plates (not shown), which cause the water to spray upwards and to the side. The water entering the channel 306 is entrained into the swirling flow of air from the bores 352 and executes a similar swirling motion, cleansing the interior surface of the bowl. The flow of air adds kinetic energy to the flow of rinse water, enhancing the cleaning action of the water. The turbulent motion of air and water in the bowl may create a mist, which may flow upwards in the space defined by the interior surface of the flange 304 and result in deposit of mist droplets on the underside of the cover 362 and on the seat 360. This upward flow of mist is inhibited by the flow of air through the grooves 358. When suction is applied to the water supply pipe 328, some air or water (depending on the filling level of the reservoir 338) is drawn from the upper compartment 340 into the pipe 328. When the liquid level in the lower compartment has fallen below the lower end of the pipe 44, air is sucked into the reservoir 338 through the vent 348. Since the air enters the lower compartment and is passing upwards through the hole 346, the lower compartment is in throttled communication with the upper compartment and the lower compartment is not refilled by gravity flow from the upper compartment during a flush but only when the flush operation is completed. When the discharge valve 6 is closed, water from the upper compartment 340 drains into the lower compartment 342, refilling the lower compartment. Thus, the reservoir 338 functions as a metering device which, at each flush, delivers a volume of water approximately equal to the volume of the lower compartment plus the volume of water in the pipes 44 and 328 above the level of the top of the lower compartment. In order to minimize variations in volume, the pipes 44 and 328 should be relatively narrow, e.g. 1.25 cm in diameter. The pipe 328 slopes downwards towards the reservoir, so that when a flush is completed, water remaining in the pipe drains back into the reservoir, minimizing grey water usage. In an aircraft, the degree of partial vacuum that is established in the toilet bowl when the discharge valve is opened can vary quite widely. Also, in some aircraft vacuum toilet systems the flush time depends on the location of the toilet bowl (forward or aft). Therefore, the reservoir 338 is designed so that at low vacuum and short flush time, the lower compartment of the reservoir is just barely emptied. At higher vacuum and/or longer flush time, the lower compartment is emptied well before the discharge valve 6 is closed. For proper functioning of the system shown in Figures 1 and 2, it is necessary that the flow resistances of the three paths for delivering air and water to the toilet bowl be balanced, so that the functions of the various flows are achieved. The proper balance is best achieved through experimentation. For example, it has been found that the greater part of the air flow should be provided through the bores 352. When the aircraft is first brought into service at the beginning of a working day, the flush control unit 180 automatically performs a power-up routine in which it opens the hand basin valve 42 for sufficient time to provide enough water to give up to five flushes. The unit 180 counts the number of flushes during the day and the number of times that the hand basin valve is opened under manual control, and utilizes this information to determine when there is a danger that the reservoir 338 is approaching an empty condition. If the flush control unit determines that the reservoir is approaching an empty condition, it causes the hand basin valve to open and provide additional water to the reservoir. In this manner, the need for a level detector in the reservoir is avoided. Moreover, because the water supplied through the outlet ports 324 is effectively distributed over the interior surface of the toilet bowl by the flow of air entering the toilet bowl, there is no need for fine spray nozzles. Furthermore, there are no valves or pumps between the reservoir 338 and the ports 324. Accordingly, the need for a filter is avoided and this in turn avoids the need to be able to backwash the filter. Of course, a strainer may be provided in the outlet of the hand basin or in the drain pipe 44 connected thereto to catch objects such as matches and buttons. The swirling flow of air that enters the toilet bowl in the system of Figures 1 and 2 is quite effective at cleansing the toilet bowl even without the aid of rinse water. Therefore, in a modification of the system of Figures 1 and 2, the flush control unit 180 is designed without the ability to count the number of flushes, so that if the reservoir runs dry, the toilet bowl is cleansed by the air flow only. In fact, the likelihood of the reservoir running dry is quite small, because normally more grey water is produced through use of the hand basin than is required for toilet flushings. The toilet system shown in Figures 1 and 2 is not restricted to use on an aircraft, and a system similar to that shown might be installed in a ship or train, for example. In the case of a system designed for use otherwise than on an aircraft, factors relating to the type of installation might dictate modifications. For example, in the case of a system on a ship, where the volume of waste is unimportant because it is pumped overboard, the pipe 328 might slope down towards the toilet bowl so that at the end of a flush, water in the pipe 328 drains into the toilet bowl and forms a pool of water. In a toilet system on a train, the degree of vacuum and the flush time is not subject to large variation, and therefore a simpler reservoir may be employed. In such a reservoir, there would be distinct upper and lower compartments, and the volume of grey water withdrawn on each flush would be determined just by the degree of partial vacuum and the flush time. When designed for use in an aircraft, a vacuum toilet system as shown in Figures 1 and 2 may be incorporated in a self-supporting module that is installed in the aircraft as a unit. The module comprises a toilet bowl and associated discharge valve, a hand basin and a reservoir. The module is self-contained except for connections to the vacuum sewer pipe, the potable water supply and, if necessary, the aircraft drain system. In the aforesaid modification of the illustrated system, where no overflow pipe is provided, relocation of the toilet module is facilitated because there is then no gravity line leaving the module. The system described and illustrated is not restricted to the particular number and arrangement of bores and grooves, and it is not essential to the invention that the grooves be directed to induce a swirling motion in the same sense as that induced by the bores. Indeed, the grooves may be directed radially, so as not to induce any swirling motion. In order to augment the swirling motion of the air that enters through the bores 352, guiding ribs may be provided at the radially outer surface of the flange 304, the ribs being inclined downwards in the counterclockwise direction. Further, although each of the illustrated systems includes an overflow for excess grey water, such an overflow is not always essential. Thus, in the case of the system shown in Figures 1 and 2, if the overflow 88 were omitted the excess grey water would flow into the bowl 2 and thence into the waste tank, and so long as the waste tank were large enough to accommodate the extra grey water, this would not present a problem.

Claims: A water supply and waste disposal system for a transport vehicle, comprising a waste-receiving bowl (2) having an outlet opening (4), a sewer pipe (8), a normally closed discharge valve (6) connecting the outlet opening (4) of the bowl (2) to the sewer pipe (8), a source of partial vacuum for establishing a lower pressure in the sewer pipe (8) than in the bowl (2), a water utilization unit (40), a water supply system (42) for providing water to the water utilization unit (40), a reservoir (338) having an inlet (44) for receiving rinse liquid from the water utilization unit (40) and an outlet (328) in communication with a rinse liquid outlet (324) in the bowl (2), the bowl (2) having a rim and a bowl cover (362) mounted for movement relative to the bowl (2) between an open position and a closed position, the cover (362) being in at least partially sealing relation with the rim when in the closed position, whereby, when the cover (362) is in the closed position and the discharge valve (6) is open, a lower pressure is created in the bowl (2), characterised in that the inlet (44) of the reservoir is exposed to substantially the same pressure (P₁) as the rinse liquid outlet (324) when the cover (362) is in the open position and the discharge valve (6) is closed, whereby rinse liquid is drawn from the reservoir (338) into the bowl (2) by way of the rinse liquid outlet (324) when the cover is in the closed position and the valve (6) is open, the bowl (2) being also provided with air supply means (302) allowing restricted entry of air into the bowl (2) when the cover (362) is in its closed position. A system as claimed in claim 1, characterised in that the reservoir (338) defines upper (340) and lower (342) compartments, the water utilization unit (40) is connected to the reservoir (338) by way of a first pipe (44), which opens into the lower compartment (342), the liquid outlet is defined by a second pipe (328) which extends from the lower compartment (342), and the lower compartment (342) is in throttled communication (via 346) with the upper compartment (340). A system as claimed in claim 2, characterised in that the second pipe (328) is formed with hole (350) that opens into the upper compartment (340). A system as claimed in any one of the preceding claims, characterised in that the air supply means (302) includes a flange (304) that extends downwardly into the bowl (2), whereby an annular channel (306) is defined between the flange and the bowl (2) and air supply bores (352) open into said annular channel, the rinse liquid outlet (324) also opening into said annular channel (306). A toilet module for a transport vehicle that comprises a water supply system (42), a sewer pipe (8) and means for establishing a partial vacuum in the sewer pipe (8), the module comprising a toilet bowl (2) having an outlet opening (4), a normally closed discharge valve (6) having an upstream side connected to the outlet opening (4) of the toilet bowl (2) and having a downstream side for connection to the sewer pipe (8), a rinse liquid outlet (324) for introducing rinse liquid into the toilet bowl (2), a wash basin (40) for receiving water from a water supply system and having a water outlet (44), a reservoir (338) having an inlet (44) for receiving rinse liquid from the wash basin (40) and an outlet (328) in communication with the rinse liquid outlet (324), the toilet bowl (2) having a rim and a toilet bowl cover (362) mounted for movement relative to the toilet bowl (2) between an open position and a closed position, the cover (362) being in at least partially sealing relation with the rim when in the closed position, whereby when the cover (362) is in the closed position and the discharge valve (6) is open, a lower pressure is created in the bowl (2), characterised in that , the inlet (44) of the reservoir is exposed to substantially the same pressure (P₁) as the rinse liquid outlet (324) when the cover (362) is in the open position and the discharge valve (6) is closed, whereby rinse liquid is drawn from the reservoir (338) into the toilet bowl (2) by way of the rinse liquid outlet (324) when the cover (362) is in the closed position and the discharge valve (6) is open, the bowl (2) being also provided with air supply means (302) allowing restricted entry of air into the toilet bowl (2) when the cover (362) is in its closed position. A module as claimed in claim 5, characterised in that the reservoir (338) defines upper (340) and lower (342) compartments, the wash basin (40) is connected to the reservoir (338) by way of a first pipe (44), which opens into the lower compartment (342), the liquid outlet is defined by a second pipe (328) which extends from the lower compartment (342), and the lower compartment (342) is in throttled communication (via 346) with the upper compartment (340). A module as claimed in claim 6, characterised in that the second pipe (328) is formed with a hole (350) that opens into the upper compartment (340). A module as claimed in any one of claims 5 to 7, characterised in that the air supply means (302) includes a flange (304) that extends downwardly into the toilet bowl (2), whereby an annular channel (306) is defined between the flange and the toilet bowl, and air supply bores (352) open into said annular channel, the rinse liquid outlet (324) also opening into said annular channel (306). A method of rinsing the toilet bowl of a vacuum sewage disposal system on a transport vehicle when the system includes a water utilization unit (40) wherein a reservoir (338) is provided to collect water leaving the water utilization unit (40) and means is employed to feed some water collected in the reservoir (338) as rinse water to the toilet bowl (2), characterised in that the flow of rinse water to the toilet bowl is accompanied by streams of air entering the bowl (2) both air and water flows being effected by a vacuum created in the bowl (2). A method as claimed in claim 9, characterised in that the air streams cause a swirling of the rinse water around the bowl (2).

Inventors: ASK ARNE, OLDFELT SVEN, STAHL GARY L, STILL BJORN MIKAEL, WALLGREN HARALD ANTON AKE, WILHELM RAYMOND L, ASK,ARNE, OLDFELT,SVEN, STAHL,GARY L., STILL,BJORN MIKAEL, WALLGREN,HARALD ANTON AKE, WILHELM,RAYMOND L.
Applicants: METRA OY AB
Application year: 1989
Main classification: B64D11
IPC codes: E03D11, E03D1, B64D11, E03B1, E03D5, E03F1