A rinse fluid valve for use in a vacuum toilet system is disclosed. The vacuum toilet system includes a waste receptacle with a rinse fluid dispenser associated therewith and a source of rinse fluid. The rinse fluid valve has a housing with an inlet in fluid communication with the rinse fluid source and an outlet in fluid communication with the rinse fluid dispenser. A flow path extends from the inlet to the outlet. A moveable rinse fluid valve member is disposed in the flow path and movable between open and closed positions. A fuse valve is disposed in the flow path upstream of the rinse fluid valve and has a normally open position to allow fluid flow therethrough. The fuse valve is actuatable to a closed position after a desired volume of fluid has passed therethrough, thereby to cease rinse fluid flow through the flow path.

FIELD OF THE INVENTION 
     The present invention generally relates to toilets and, more particularly, to vacuum toilet systems. 
     BACKGROUND OF THE INVENTION 
     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 “bench test” 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. 
     SUMMARY OF THE INVENTION 
     In accordance with certain aspects of the present invention, a rinse fluid valve is provided for use in a vacuum toilet system having a waste receptacle with a rinse fluid dispenser associated therewith and a source of rinse fluid. The rinse fluid valve comprises a housing having an inlet in fluid communication with the rinse fluid source and an outlet in fluid communication with the rinse fluid dispenser. A flow path extends from the inlet to the outlet, and a moveable rinse fluid valve member is disposed in the flow path and moveable between open and closed positions. A second valve member is disposed in the flow path upstream of the rinse fluid valve and has a normally open position to allow fluid flow therethrough. The second valve member is actuatable to a closed position after a desired volume of fluid has passed therethrough thereby to cease rinse fluid flow through the flow path. 
     In accordance with additional aspects of the present invention, a rinse fluid valve is provided for use in a vacuum toilet system having a waste receptacle with a rinse fluid dispenser associated therewith and a source of rinse fluid. The rinse fluid valve comprises a housing having an inlet in fluid communication with the rinse fluid source and an outlet in fluid communication with the rinse fluid dispenser. A flow path extends from the inlet to the outlet, and a moveable rinse fluid valve member is disposed in the flow path and moveable between open and closed positions. A second valve is disposed in the flow path upstream of the rinse fluid valve, the second valve including a second valve member moveable between an open position allowing fluid flow therethrough and a closed position prohibiting fluid flow therethrough. A position sensor is provided for detecting a position of the second valve member and generating a position signal. 
     In accordance with further aspects of the present invention, a rinse fluid valve is provided for use in a vacuum toilet system having a waste receptacle with a rinse fluid dispenser associated therewith and a source of rinse fluid. The rinse fluid valve comprises a housing having an inlet in fluid communication with the rinse fluid source and an outlet in fluid communication with the rinse fluid dispenser. A flow path extends from the inlet to the outlet, and a moveable rinse fluid valve member is disposed in the flow path having a flow passage extending therethrough. The valve member is moveable between a closed position, in which the flow passage does not communicate with the flow path to prevent fluid flow, and an open position, in which the flow passage is aligned with the flow path to allow fluid flow. A freeze protection valve is formed in the ball valve and has a valve seat and a movable valve member biased away from the valve seat, wherein sufficient fluid flow pressure drives the valve member into engagement with the valve seat. 
     Other features and advantages are inherent in the apparatus claimed and disclosed or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B are perspective views of a vacuum toilet incorporating a rinse fluid valve in accordance with the present invention. 
     FIG. 2 is a schematic diagram of the vacuum toilet of FIG.  1 . 
     FIG. 3 is an enlarged perspective view of a valve set incorporating the rinse fluid valve. 
     FIG. 4A and 4B are perspective views of a discharge valve and actuator incorporated into the valve set. 
     FIG. 5 is a side elevation view, in cross-section, of the rinse fluid valve incorporated into the valve set. 
     FIGS. 6A-D are side elevation views, in cross-section, of the rinse fluid valve showing the various stages of a rinse cycle. 
     FIG. 7 is an side elevation view, in cross-section, of an alternative embodiment of a ball valve incorporated into the rinse fluid valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A vacuum toilet  10  is illustrated in FIGS. 1A,  1 B, and  2  having a valve set  8  with a rinse fluid valve  72  in accordance with the present invention. The vehicle is provided with a sewer line  1 l, a vacuum tank  13  connected to the sewer line  11 , and a vacuum source (not shown) for placing the vacuum tank  13  under partial vacuum pressure. The vehicle further includes a source of rinse fluid  15  connected to a rinse fluid supply line  19 . 
     The vacuum toilet  10  includes a bowl  36  for receiving waste material connected to the valve set  8 . In the preferred embodiment, the bowl  36  is supported by a frame  20  to form a replaceable bowl assembly, as described in greater detail in commonly owned and co-pending U.S. patent application Ser. No. 09/713,861, entitled “Toilet Bowl Assembly” incorporated herein by reference. The frame  20  preferably includes a bracket  27  adapted to support the valve set  8 . The valve set  8  may be attached to the bracket  27  using fasteners that may be manipulated by hand, such as knurled screws  37 . At least one rinse fluid dispenser, such as nozzles  46 , is provided inside the bowl  36  for directing rinse fluid over the surface of the bowl. A first rinse fluid pipe  35   a  connects the nozzles  46  to a vacuum breaker  33 . A second rinse fluid pipe  35   b  extends from the vacuum breaker  33  to the valve set  8 . Quick-disconnect couplings  108   a,    108   b  are provided to connect the first and second rinse fluid pipes  35   a,    35   b  to the vacuum breaker  33 . 
     As shown in FIG. 3, the valve set  8  comprises four sub-components: a discharge valve  70 , a rinse valve  72 , a flush control unit (FCU)  74 , and an actuator  76 . The discharge valve  70  includes a discharge valve housing  78  divided into two halves  78   a,    78   b.  As best shown in FIGS. 4A and 4B, the housing  78  includes a pair of inlets  79 ,  80  formed in the housing half  78   a  aligned with a pair of outlets  81 ,  82  formed in the housing half  78   b.    
     The housing  78  further defines a chamber for receiving a discharge valve member, such as valve disk  83 . An axle  84  is attached to the valve disk  80  and has two ends  84   a,    84   b.  Holes are formed in the housing halves  78   a,    78   b  sized to receive the axle ends  84   a,    84   b,  respectively, so that the disk  83  is supported for rotation about the axle  84 . The periphery of the disk  83  is formed with gear teeth  85 , and a pair of apertures  86 ,  87  are formed through the disk  83 . The apertures  86 ,  87  are spaced so that both register simultaneously with the associated inlet/outlet pairs  79 / 81 ,  80 / 82  as the disk  83  rotates. In the illustrated embodiment, the apertures  85 ,  86  and associated inlet/outlet pairs  79 / 81 ,  80 / 82  are spaced 180 degrees apart. 
     According to the illustrated embodiment, the inlet  79  is connected to one end of a transfer pipe  44 , with the other end of the transfer pipe  44  being attached to an outlet  42  of the bowl  36 . In the preferred embodiment, the transfer pipe  44  includes a fitting  47  (FIG. 1A) adapted to frictionally and sealingly engage the bowl outlet  42 , so that the transfer pipe  44  may be quickly and easily attached and removed from the bowl outlet  42 . An air intake check valve  45  is attached to the other inlet  80 , and is oriented to allow fluid flow into the inlet  80  while preventing fluid from discharging out of the check valve  45  (FIGS.  1 A and  2 ). A U-shaped outlet pipe  12  (FIG. 1B) has a first end connected to the outlet  81  and a second end connected to the outlet  82 . The outlet pipe  12  further has a branch  17  leading to a discharge pipe  21 . In the preferred embodiment, the branch  17  includes a pair of spaced pins and the discharge pipe  21  includes a pair of J-shaped slots positioned to engage the pins, so that the discharge pipe  21  is removably attached to the branch  17 . Furthermore, when the pins and J-shaped slots are spaced 180 degrees apart, the discharge pipe  21  may be positioned for either right- or left-handed discharge simply by rotating the discharge pipe  21  before attachment, without requiring changes to the other toilet components. The free end of the discharge pipe  21  is adapted for releasable connection to the sewer line  1 , such as with a clam shell coupling (not shown). 
     In operation, when the disk apertures  86 ,  87  are aligned with the inlet/outlet pairs  79 / 81 ,  80 / 82 , the discharge valve  70  not only transfers waste from the drain pipe  44  to the sewer line  11 , but also pulls additional air into the sewer line  11  through the air intake check valve  45 . The additional air intake reduces noise that is normally generated during a flush. 
     The actuator  76  is provided for driving the valve disk  83 . As best shown in FIG. 4A, the actuator  76  includes a spur gear  90  enmeshed with the gear teeth  85  formed about the periphery of the disk  83 . The spur gear  90  is mounted to a rotatable shaft  92 , and a drive is provided for rotating the shaft  92 . The FCU  74  is operably coupled to the actuator  76  to control operation of the actuator. According to the illustrated embodiment, the disk  83  may be rotated in a single direction by ninety degree increments to open and close the discharge valve  70 . Alternatively, the disk  83  may also be reciprocated back and forth across a ninety degree arc to open and close the valve  70 , or the disk  83  may be controlled in other manners according to other disk designs and layouts. 
     The rinse valve  72  is provided for controlling flow of rinse fluid to the bowl  36 . As best shown in FIG. 5, the rinse valve  72  comprises a housing block  100  formed with an inlet bore  101  defining an inlet  102  and an outlet bore  103 . The inlet bore  103  is adapted for connection to the rinse fluid line  19  via a quick-disconnect coupling (not shown). An insert  104  is positioned in a downstream portion of the outlet bore  103  and defines an outlet  105 . The outlet end of the insert  104  is barbed to secure one end of the second rinse fluid pipe  35   b  thereto, while the opposite end of the second rinse fluid pipe  35   b  has the quick-disconnect coupling  108   b  (FIGS.  1 A and  1 B). A poppet valve bore  106  is also formed in the housing block  100 , and fluidly communicates with the inlet bore  101 . An annular recess  107  is formed in the housing block  100  concentric with the poppet valve bore  106  to establish fluid communication between the poppet valve bore  106  and the outlet bore  103 . 
     The rinse valve  72  includes a rinse valve member, such as a ball valve  110 , which is disposed in the outlet bore  103  for selectively establishing fluid communication between the outlet bore  103  and the outlet  105 . The ball valve  110  includes a shaft  111  and a valve member  112  having a flow passage  113  extending therethrough. A seal  114  is provided downstream of the valve member  112  for preventing leakage between the valve member  112  and the downstream portion of the outlet bore  103 . As shown in FIG. 5, the flow passage  113  is perpendicular to the outlet bore  103 , thereby preventing fluid flow. The ball valve  110  is rotatable, however, to align the flow passage  113  with the outlet bore  103 , thereby establishing fluid communication between the upstream portion of the outlet bore  103  and outlet  105 . 
     The top of the shaft  111  is adapted to mechanically engage the axle end  84   a,  as best shown in FIG. 3, so that rotation of the disk  83  also rotates the ball valve  110 . In the illustrated embodiment, the shaft  111  is formed with a key  115 , while the hub end  84   a  has a slot  116  sized to receive the key  115 . As a result, a separate actuator is not required to actuate the ball valve  110 , thereby reducing cost and space requirements for the toilet. 
     The rinse valve  72  further includes a fuse valve  120  for metering rinse fluid flow through the rinse valve when the ball valve  110  is open. As used herein, the phrase “fuse valve” indicates a valve that actuates after a set value of fluid has passed therethrough. As best shown in FIG. 5, a bonnet  121  is attached to the housing block  100  to close off the poppet valve bore  106  and the recess  107 . A flexible diaphragm  122  is attached between the housing block  100  and the bonnet  121  to define a pilot chamber  117  above the diaphragm  122  and a flow chamber  118  below the diaphragm  122 . As shown in FIG. 5, the diaphragm  122  is in a closed position, in which the diaphragm  122  engages an annular intermediate wall  123  extending between the poppet valve bore  106  and recess  107 , thereby closing off fluid communication between the poppet valve bore  106  and recess  107 . A poppet valve  124  is disposed inside the poppet valve bore  106  and is attached to the diaphragm  122 , so that the poppet valve  124  moves with the diaphragm  122 . The top of the poppet valve  124  is formed with a pilot port  125 , and flow ports  126  extend radially through a sidewall of the poppet valve  124 . A spring  127  is disposed in the poppet valve port for biasing the diaphragm  122  away from the intermediate wall  123  toward an open position, in which fluid communication is established between the poppet valve bore  106  and the recess  107 . 
     The fuse valve  120  limits the amount of rinse fluid allowed to flow through the rinse valve  72  when the ball valve  110  is open. During operation, the ball valve  110  is normally in a closed position to prevent flow of rinse fluid through the rinse valve  72 . The rinse fluid flows through both the pilot port  125  to register at the pilot chamber  117 , and through the flow ports  126  to register in the flow chamber  118 . Because there is no rinse fluid flow, the rinse fluid pressure is the same in both the pilot chamber  117  and the flow chamber  118 , so that the spring  127  urges the diaphragm  122  and poppet valve  124  to the open position, as shown in FIG.  6 A. 
     In response to a flush command, the ball valve  110  is rotated to the open position so that the ball valve flow passage  113  communicates the outlet bore  103  to the outlet  105 , thereby creating fluid flow through the valve  72  (FIG.  6 B). During fluid flow, the rinse fluid experiences a pressure drop as it passes through the flow ports  126 , thereby reducing the fluid pressure in the flow chamber  118  while the pressure in the pilot chamber  117  stays substantially the same. The resulting pressure differential across the diaphragm  122  ultimately overcomes the force of the spring  127  SO that the diaphragm  122  and poppet valve  124  move to the closed position, as shown in FIG.  6 C. When the diaphragm is in the closed position, fluid flow through the rinse valve  72  is again cut off, this time by the engagement of the diaphragm  122  with the intermediate wall  123 . Because of the fuse valve  120 , the volume of rinse fluid passing through the open ball valve  110  is substantially constant from flush to flush, regardless of the rinse fluid pressure supplied to the rinse valve  72 . It will also be appreciated that the fuse valve  120  provides a redundant shut-off, so that the ball valve  110  or the fuse valve  120  may be used to stop rinse fluid flow should the other fail. 
     The rinse valve  72  further includes a face valve  130  for returning the diaphragm  121  back to the open position after the ball valve  110  is subsequently closed. Referring to FIG. 5, a bypass bore  131  is formed in the housing block  100  that connects the inlet bore  101  to an auxiliary bore  132 . A reset bore  134  intersects the bypass bore  131  and communicates with a ball valve bore  135  formed in the housing block  100 . A reset insert  136  is inserted in the reset bore  134  and has a top surface adapted to engage a bottom of the ball valve  110 . The ball valve  110  is formed with reset passages  137  extending into the ball valve  110  to a transverse passage  138  extending entirely through the ball valve  110 . The reset passages  137  are located on the ball valve  110  so that they align with the reset insert  136  only when the ball valve  110  is in the closed position. The seal  114  prevents rinse fluid from leaking from the transverse passage  138  to the outlet  105 . No seal is provided upstream of the ball valve  110  so that, when one of the reset passages  137  is aligned with the insert  136 , fluid communication is established from the inlet bore  101 , through the bypass and reset bores  131 ,  134  and one of the reset passages  137  to the flow chamber  118 . 
     According to the illustrated embodiment, the rinse valve  72  also includes a drain valve  133  disposed in the auxiliary bore  132  to provide freeze protection, as is well known in the art. 
     In operation, the diaphragm  121  moves to the closed position while the ball valve  110  is open, thereby stopping rinse fluid flow through the rinse valve  72  (FIG.  6 C). With the ball valve  110  in the open position, neither reset passage  137  is aligned with the reset insert  136 . The ball valve  110  is subsequently closed, thereby aligning one of the reset passages  137  with the insert  136  and establishing fluid communication from the inlet bore  101  to the flow chamber  118  (FIG.  6 D). The incoming rinse fluid pressure registers at the flow chamber  118 , so that the flow chamber reaches the same pressure as the pilot chamber  117 . With the differential pressure across the diaphragm  121  removed, the spring  127  is again allowed to urge the diaphragm  121  to the open position, thereby resetting the fuse valve  120  to the position shown in FIG.  6 A. 
     In the preferred embodiment, a position sensor is used to provide feedback regarding poppet valve position feedback. In the illustrated embodiment, a magnet  140  is attached to the poppet valve  124 , and a hall effect switch  141  is located outside of the bonnet  121  in a switch enclosure  142  attached to the bonnet  121 . The hall effect switch  141  provides a signal that varies according to the position of the magnet  140  to indicate the position of the poppet valve  124 . The poppet valve position signal may be used for diagnostic purposes such as fault detection by comparing the position signal to the position of the disk  83  or ball valve  110 . For example, if the poppet valve  124  does not return to the open position when the ball valve  110  resumes the closed position, a signal may be sent by the FCU to the vehicle indicating a problem with the rinse fluid valve  72 . 
     In an alternative embodiment illustrated at FIG. 7, instead of providing the separate drain valve  133 , the freeze protection is incorporated directly into the ball valve  210 . The ball valve  210  has a shaft  211  and a valve member  212  with a flow passage  213 . A seal  214  is provided for sealing the downstream portion of the valve member  212  from the outlet bore. The ball valve  210  preferably includes a key  215  for engaging the slot  116  formed in the axle end  84   a,  so that operation of the ball valve  210  is similar to the previous embodiment. 
     A first angled passage  220  extends from a periphery of the valve member  212  to a center line  221  of the ball valve  210 . A second angled passage  222  extends from an opposite portion of the valve member periphery to the same center line  221 , so that the second angled passage  222  intersects the first angled passage  220 . A ball stop  223  is sized to freely move within the first and second passages  220 , 222 , and first and second sleeves  224 ,  225  are inserted into the first and second angled passages  220 ,  222 , respectively, and sized to frictionally engage the first and second passages  220 ,  222 , thereby retaining the ball stop  223  within the passages  220 , 222 . With the sleeves  224 ,  225  in position, the ball stop  223  is free to shuttle therebetween. The sleeves  224 , 225  each have a central passage  226  and a valve seat  227  formed therein. The valve seats  227  are sized to sealingly engage the ball stop  223  and prevent fluid flow therethrough. A leaf spring  228  is provided with a first arm  229  extending into the first angled passageway  220  and a second arm  230  extending into the second angled passageway  222 . The arms  229 ,  230  urge the ball stop  223  away from the valve seats  227  to allow fluid flow therethrough. When a sufficient fluid pressure acts on the ball stop  223 , however, the urging force of the arms  229 ,  230  is overcome and the ball stop  223  engages one of the seats  227 . 
     In operation, the ball stop  223  is urged by one of the leaf spring arms  229 ,  230  away from an associated sleeve seat  227  in the absence of rinse fluid flow. When rinse fluid begins to flow, the fluid force overcomes the leaf spring force to drive the ball stop  223  into engagement with one of the sleeve seats  227 , thereby preventing fluid flow through the first and second angled passages  220 ,  222 . Once fluid flow subsequently ceases, the fluid force is removed and the spring again urges the ball stop  223  away from the seats  226 , thereby allowing air flow through the passages  220 ,  222 . 
     The FCU  74  comprises a housing  150  attached to the discharge valve housing half  78   b  opposite the rinse valve  72  (FIG.  3 ). The housing  150  encloses one or more circuit boards (not shown) for controlling operation of the toilet  10 . In addition to the typical inputs and outputs, the FCU 74  also receives feedback from the poppet valve position sensor  141 . 
     The FCU housing  150  further houses a position sensor for determining the position of the disk  83 . As best shown in FIG. 4A, magnets  152  are attached to the axle end  84   b  of the disk  83 . The axle end  84   b  extends into the FCU housing  150 , so that the magnets  152  are positioned proximal the control board. Hall effect switches  154  are provided directly on the circuit board for sensing the magnets  152  and thus determining the rotational position of the disk  83 . In the illustrated embodiment, a pair of magnets  152  are attached to the axle end  84   b,  and a pair of hall effect switches  154  are attached to the circuit board. The switches  154  actuate between on and off positions depending on the proximity of the magnets, thereby indicating the position of the disk  83 . As a result, the position of the disk  83  is directly sensed rather than inferring disk position based on actuator position. In addition, the switches  154  are located inside the FCU housing  150  and are therefore isolated from contamination due to lubrication or other material. 
     From the foregoing, it will be appreciated that the rinse valve  72  of the present invention provides a relatively constant volume of rinse fluid to the bowl  36 . The use of a ball valve  110  and a fuse valve  120  provides a redundant shut-off in the system in the event one of the valves fails in the open position, thereby preventing constant flow of rinse fluid. The rinse valve also includes a sensor for providing feedback regarding fuse valve position, which may be used to diagnose faults in the valve. In addition, compact freeze protection apparatus is described. 
     The foregoing detailed description has be given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications would be obvious to those skilled in the art.