The present invention generally relates to toilets and, more particularly, to vacuum toilet systems.
Vacuum toilet systems are generally known in the art for use in both vehicle and stationary applications. A vacuum toilet system typically comprises a bowl for receiving waste having an outlet connected to a vacuum sewer line. A discharge valve is disposed between the bowl outlet and vacuum sewer line to selectively establish fluid communication therebetween. The vacuum sewer line is connected to a collection tank that is placed under partial vacuum pressure by a vacuum source, such as a vacuum blower. When the discharge valve is opened, material in the bowl is transported to the sewer pipe as a result of the pressure difference between the interior of the bowl and the interior of the sewer line. Conventional vacuum toilet systems also include a source of rinse fluid and a rinse fluid valve for controlling introduction of rinse fluid into the bowl.
It is important for a rinse valve fluid to deliver a consistent volume of rinse fluid during each flush cycle, particularly in vehicle applications where the source of rinse fluid and the waste storage capacity are limited. If too little rinse fluid is sent, the bowl will not be sufficiently rinsed. If too much fluid is delivered, the rinse fluid supply is more quickly depleted and the waste storage capacity is reached sooner. Accordingly, the rinse fluid valve should consistently deliver the desired volume of rinse fluid during each flush cycle.
Conventional rinse fluid valves, however, deliver inconsistent volumes of rinse fluid during a flush cycle. A rinse valve is typically provided as an electrically operated valve, such as a solenoid valve. The valve has a normally closed position and is controlled to actuate to an open position for a fixed period of time to allow rinse fluid to flow to the bowl. Thus, the volume of rinse fluid delivered by the rinse fluid valve is dependent on the pressure of the rinse fluid entering the valve, since the open valve period is fixed. Unfortunately, rinse fluid pressure is not always held constant. A system may experience pressure fluctuations during operation, and different systems may provide different rinse fluid pressure levels. As a result, the rinse fluid valves deliver different volumes of rinse fluid according to the rinse fluid pressure.
Furthermore, conventional rinse fluid valves are subject to failure, which may flood the toilet and prematurely deplete the rinse fluid supply. The rinse fluid valve may become stuck in an open position so that rinse fluid is continuously supplied to the toilet bowl. If the valve failure is not detected quickly, the bowl may flood with rinse fluid and overflow.
Still further, conventional vacuum toilets in general and rinse fluid valves in particular are overly difficult and time consuming to maintain. Maintenance concerns are particularly significant in aircraft applications, in which a number of sub-systems are installed on board. According to general practice in the airline industry, each sub-system includes one or more components which must be replaced in the event of failure, such components being commonly referred to as line replaceable units (LRUs). Presently, the entire toilet assembly is defined as the LRU for the vacuum toilet system. As a result, an airline must stock one or more replacement toilets in case of a toilet failure, so that the replacement toilet may be swapped in for the faulty toilet. A xe2x80x9cbench testxe2x80x9d is then performed on the faulty toilet to determine which components have failed in the toilet. The faulty components are then repaired or replaced (which may include significant disassembly and reassembly of the toilet) so that the toilet may be reused on another aircraft.
Each of the steps performed during a toilet repair is overly difficult and time consuming. To remove an entire toilet assembly from an aircraft requires disassembly of at least four self-locking mounting fasteners, an electrical connection, a grounding strap, a potable water line connection, and a waste discharge pipe connection. Each connection may be difficult to access, and may require a particular tool in order to loosen and disconnect. The same connections must then be reconnected for the replacement toilet.