in fig1 a mask frame is shown generally at 10 . the mask is designed to be worn on a patient &# 39 ; s face and is secured by means of straps ( not shown ) received by attachment points 18 . a conduit end assembly is shown generally at 20 , including an elbow part 26 having at one end thereof a combined vent / connector piece 28 . the elbow and vent / connector piece together form a housing for an anti - asphyxia valve ( as will be further discussed ) or other internal components ( not shown ). at the other end of the elbow is a detachable swivel tube 29 for connection of the gas delivery conduit ( not shown ). the mask 10 includes a circular aperture 12 sized to receive a mating portion 22 of the vent / connector piece 28 . the mating portion 22 has an annular groove 23 formed therein that receives a locking means 30 in the form of a c - shaped clip attached after mating to the mask . the clip 30 has an outside diameter greater than the width of the aperture 12 and an inner diameter adapted to ensure a snug fit within the annular groove 23 . the clip 30 is resilient and can expand sufficiently to allow the clip to be fitted into and removed from the groove 23 . as shown in fig1 , the clip 30 is located onto the mating portion 22 on the inside of the mask 10 . in this position , the clip 30 is inaccessible while the mask is being worn by a patient . once the mating portion 22 of the vent / connector piece 28 has been inserted through the aperture 12 and the locking clip placed in the annular groove , the conduit end assembly 20 and the mask 10 cannot be separated without first removing the mask from the patient . an exploded view of one embodiment of the anti - asphyxia valve and conduit connector assembly is shown in fig2 . as illustrated in fig2 , the end of the elbow 26 adjacent the mask 10 is fitted with an anti - asphyxia valve arrangement that provides an air passage to the patient in the event of failure of the gas delivery apparatus , consisting of a valve membrane 27 fitted into the end of elbow 26 and vents 31 in the vent / connector piece 28 . during proper operation of the gas delivery system , the valve membrane remains in the orientation shown in fig2 , closing off the vents 31 . in the event of a drop in pressure below a predetermined level , the valve membrane 27 flips to a reverse orientation , opening the vents 31 . the construction and operation of the anti - asphyxia valve is described in more detail in the applicant &# 39 ; s australian patent application no . 65527 / 99 , the contents of which are incorporated herein by reference and described herein . resilient detents 42 on the elbow 26 pass through and engage behind slot - forming formations 44 in the vent / connector piece 28 to provide releasable engagement of the two parts . the vent / connector piece has a collar 47 that abuts a corresponding surface of the mask 10 to limit the distance that the vent / connector piece can be inserted into the mask aperture 12 ( fig1 ). the corresponding surface is an annulus 50 having a protruding rim 51 the outer circumference of which preferably engages the inner surface of the detents 42 on insertion of the mating portion 22 into the aperture 12 . this engagement prevents the detents from being pushed radially inwards sufficiently for the detents to disengage from behind the slot - forming formations 44 , thus preventing the elbow 26 and vent / connector piece 28 from separating whilst still attached to the mask frame 11 , for example during patient treatment . the result of this is that the anti - asphyxia valve arrangement cannot be disassembled without first removing the elbow and vent / connector piece assembly from the mask . however , once disconnected from the mask , the assembly may be readily separated for cleaning and then reassembled . the other , distal end of elbow 26 has an enlarged diameter portion which receives the swivel tube 29 , onto which a flexible gas conduit ( not shown ) may be fitted . the swivel tube 29 has a pair of flanges 56 and 57 defining an annular groove 58 therebetween . the end of swivel tube 29 is inserted into the elbow 26 until the end flange 57 abuts an inner surface ( not shown ) within elbow 26 . in this position the annular groove 58 is at least partially aligned with an annular groove 61 in the exterior of the elbow , which receives a swivel clip 41 . the swivel clip 41 has an inner diameter only slightly greater than the diameter of the groove 61 , to ensure a snug fit within the groove . the clip 41 is resilient to permit sufficient expansion for attachment and removal of the clip from the groove . the groove 61 has slots 59 which receive lugs 62 on the clip . these lugs rotatably engage in the groove 58 between flanges 56 and 57 of the swivel tube . the swivel tube arrangement thus acts as a rotatable coupling between the conduit and the elbow whilst allowing quick attachment and removal of the gas conduit from the elbow regardless of whether the assembly is attached to the mask at the time . as shown in fig3 , the mask includes a mask frame 11 , cushion 13 and cushion clip 14 . the cushion is received on a rib 15 extending around the periphery of the mask frame 11 . the cushion is held to the rib by the cushion clip 14 . the mask frame includes attachment points 18 that receive straps ( not shown ) for attaching the mask to the patient , an aperture 16 for receiving an air vent 17 , and measurement ports 19 . the details of construction and of the operation of the anti - asphyxia valve will now be described with reference to fig4 . as illustrated in fig4 , a flow generator 100 having a flexible air flow conduit 112 is secured to an embodiment of a valve 114 which is thereafter connected to a nasal mask 116 of a patient 121 . the mask 116 illustrated in fig4 includes a mask cushion 117 and a co . sub . 2 gas washout vent 119 and is just one example of numerous types of patient interface . as described above , the mask may be designed to cover the patient &# 39 ; s face . the location of the valve 114 shown in fig4 is just one example of numerous possible locations . the valve 114 could be connected to the mask 116 as shown in fig4 and 8 , or it could be an integral part of the mask 116 , as shown in fig1 . there could also be two or more valves located on a single system . it is preferred to put the valve 114 as close to the mask 116 as possible , or to make it part of the mask 116 . the flow generator 100 produces a flow of breathable gas , typically air , and can be an electric blower , a controlled bottled gas system , a ventilator , or any other type of device that delivers breathable , therapeutic or anaesthetic gas . the valve 114 shown in fig4 to 7 is comprised of two housing parts 118 and 120 which may be locked together by way of respective male and female bayonet fittings 122 and 124 . the housing part 118 includes an inlet in the form of frusto - conical portion 126 . the housing part 120 includes an outlet in the form of frusto - conical portion 128 . the portions 126 and 128 allow push - on assembly and frictional engagement with the gas supply conduit 112 and the mask housing 116 respectively . the housing part 120 includes six peripherally arranged ports 130 each separated by one of six connecting members 131 . a flexible flap 132 of generally round cross - section is formed from a silicone rubber and has a central orifice 133 . the flap 132 includes a first portion in the form of outer rim 134 . the flap 132 is glued , clamped or otherwise attached or mounted to the second housing part 120 at the outer rim 134 . the flap 132 includes a second portion in the form of flexible flaps 135 . as shown in fig6 a , when the difference in the gas pressure between the housing interior and atmosphere is below a predetermined operating threshold of , for example 2 cm h 2 o , the flaps 135 are in a relaxed state and inherently biased to an “ open ” position allowing gas flow from the interior of the housing through the ports 130 and to atmosphere . accordingly , if the supply of breathable gas falls below the threshold or ceases , the patient 121 is still able to inhale air through the open ports 130 and exhale carbon dioxide out through the open ports 130 , as indicated by arrows 129 . when the breathable gas supply commences or resumes and the difference in the gas pressure between the housing interior and atmosphere builds up to equal or above 2 cm h 2 o the flaps 135 move to a “ closed ” position occluding the ports 130 shown in fig7 . thereafter the flaps 135 are maintained closed by the gas pressure in the housing interior being above the predetermined operating threshold . in this closed position all the gas supplied from the flow generator 100 can pass through the orifice 133 of the flap 132 to be delivered to the mask 116 of the patient 121 , as indicated by arrows 139 . in the embodiment shown in fig4 to 7 , the flap 132 has three of the flaps 135 which each subtend an angle of approximately 120 °. the three flaps 135 are each separated by slits 136 ( only one of three slits 136 shown ). the slits 136 allow the flaps 135 to flex between the open and closed positions , as shown in fig6 a and fig7 respectively , without crinkling or binding . every second one of the six connecting members 131 includes a flange 137 which abuts adjacent outer edges ( adjacent the slits 136 ) of each of the flaps 135 in the closed position to assist in sealing the ports 130 . each flap 132 is preferably manufactured by moulding of a single silicone rubber component in the shape shown in fig6 a ( i . e . the open position ). the flaps 135 are preferably 0 . 15 mm thick . the thickness of each of the flaps is adjusted to suit their application and , in particular , the pressure of the operating threshold . if too flimsy , the flaps will distend or crumple across the ports 130 and may not move to return from the closed position at the correct pressure . if too stiff , the flaps will not move to the closed position at the correct pressure . testing of a prototype of the valve 114 shown in fig4 to 7 was conducted with a flow generator connected to the inlet cylindrical portion 126 via an air flow conduit . a mask was connected to the valve 114 at the outlet cylindrical portion 128 . the mask cushion seals the mask interior relative to the wearer &# 39 ; s face such that the only gas flow from the mask 116 to atmosphere is through the mask gas washout vent . with this arrangement the flap assembly 132 closed the ports 130 at an approximately 2 cm h 2 o pressure difference ( operating threshold ) between the interior of the valve 114 and atmosphere . the inherent resilience of the silicone rubber flaps 135 re - opened the ports 130 when the pressure difference ( operating threshold ) between the interior of the valve 114 and atmosphere fell below approximately 2 cm h 2 o . fig6 b shows the flap assembly 132 in the open position when the flow generator is operating but the pressure difference between the valve interior and atmosphere is below the operating threshold . under these conditions , some of the supplied gas passes through the ports 130 and the remainder passes through the valve outlet 128 to the mask , as indicated by arrows 127 and 139 respectively . as the flow through the valve outlet 128 is thus less than the supplied flow through the valve inlet 126 , a pressure differential is created between the downstream side of the flaps 135 ( that side adjacent the valve outlet 128 ) and the upstream side of the flaps 135 ( that side adjacent the valve inlet 126 ) which forces the flaps 135 to deform against their inherent resilience towards the ports 130 and , ultimately , to the closed position shown in fig7 . when in the closed position shown in fig7 , there is no gas flow through the ports 130 . under these conditions , a pressure differential between the valve interior and atmosphere above the operating threshold will maintain the flaps 135 in the closed position . the inherent resilience of the flaps 135 moves the flaps 135 away from the ports 130 and towards the open position when the pressure difference between the valve interior and atmosphere falls below the operating threshold . fig8 illustrates another embodiment in which the valve 114 is attached to another type of mask 116 that includes a co 2 gas washout vent 138 . fig9 illustrates an embodiment of the valve 114 having a unitary housing 140 . fig1 illustrates another embodiment of the valve 114 having a unitary housing 140 and a swivel connector 142 that snap - engages with the cylindrical portion 128 over resilient fingers 144 . this embodiment obviates the need for a separate swivel connector elsewhere in the gas supply circuit . in another embodiment ( not shown ) the swivel connection 142 is used in conjunction with the unitary housing 140 . fig1 illustrates a further embodiment of the valve 114 incorporated into a mask 146 having a mask shell 148 and a mask cushion 150 . in this embodiment , the valve 114 is integrally formed with the mask shell 148 thereby obviating the push - on connection between the mask 116 and the valve 114 . fig1 shows an embodiment of the flap 132 which includes an external rim 152 of stepped cross section which assists in locating the flap 132 in the housing . the rim 154 is received within a corresponding recess in the housing to facilitate locating and mounting the flap 132 in the housing . fig1 shows another embodiment of the flap 132 having an internal rim 154 of rectangular cross section . fig1 and 19 show yet another embodiment of the flap means 132 having a substantially cylindrical formation 156 between the flaps 135 and the rim 152 . the cylindrical formation 156 and the rim 152 facilitate locating the flap 132 with correct orientation in the housing . fig1 illustrates a further embodiment of the flap 132 which includes a series of pleats or folds 160 which flex to allow movement of the flap 132 between the open and closed positions . fig1 shows another embodiment of the flap 132 similar to that shown in fig1 but without the slits 136 . this embodiment thus has only a single flap 135 which distorts when moving between the open and closed positions . fig1 shows an embodiment similar to that of fig1 but including three rows of perforations 158 which provide localised flexibility to assist in movement of the flaps 135 between the open and closed positions . fig1 shows an embodiment of a flap 132 that has the cylindrical formation 156 of the embodiment of fig1 and 19 and the pleats or folds 160 of the embodiment of fig1 . fig2 and 21 show a further embodiment of a flap 132 with a single flap 135 that includes a number of radial protuberances &# 39 ; or ribs 162 of greater thickness than the flap 135 . in the embodiment shown , the ribs 162 are of equal thickness . in other embodiments ( not shown ) the ribs are of unequal thickness and , for example , can be thicker on one side for operation in applications where flow is different across the flap such as in a curved or angled conduit or the like . fig2 and 23 show examples of the cross section the flap 135 can assume in the closed position . fig2 shows an example of the cross section that the ribs 162 can assume in the open position . fig2 and 27 are schematic views of another embodiment of a flap 132 that includes a one - way valve device 164 adapted to only allow gas flow in the direction of the patient . the one - way valve device 164 is known as a non - rebreathe valve . fig2 and 27 show the flap 132 in the closed position and the one - way valve 164 in the open position , thereby allowing gas flow to the patient , as indicated by arrows 166 . fig2 shows the flap 132 in the open position and the one - way valve 164 in the closed position , thereby directing all of the gas flow directed through the ports of the valve to atmosphere . another embodiment of the invention ( not shown ) includes a port or series of ports that function as both the flap assembly ports and the mask co 2 gas washout port . in this embodiment , the ports and the flap assembly are sized so each port is not totally occluded by the flap assembly in the closed position . accordingly , in the closed position each port is occluded to an extent that it is of a size suitable to function as the mask co 2 gas washout vent . when the pressure differential between the interior of the valve and atmosphere is below the operational threshold , the flap assembly moves to the open position and each port to atmosphere is enlarged to a size suitable to function as the anti - asphyxia port . one advantage is that the valve can be used with nasal , mouth mask and full face ( nose and mouth ) mask systems for both adults and infants . in the situation of infants , the airflow is generally less , and thus the force needed to flex the flap assembly into the closed position is lowered accordingly . the valve according to the present invention can be used for any type of air delivery system , it is preferably used in cpap applications for the treatment of osa or nippv . preferred embodiments of the valve of the present invention have the advantage of being able to operate independent of orientation . that is , although the valve has to be connected in the right direction between the flow generator and the mask , it can be inverted , held sideways , etc . which often occurs during the time when the patient sleeps . another advantage of the valve of the present invention is it may have only one moving or flexing part providing consistent operation . further , the valve can be disassembled , cleaned and reassembled very easily at home or at a hospital or clinic due to it having less parts . the valve of the present invention is also very quiet in operation . while particular embodiments of this invention have been described , it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof . the present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive , the scope of the invention being indicated by the appended claims rather than the foregoing description , and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein .
a flow regulation vent for venting washout gas to atmosphere and for regulating flow from a pressurized gas supply includes a fixed portion adapted to engage a gas supply conduit ; a spring force biased movable portion in communication with the pressurized gas supply ; and a hinge pivotally connecting the movable portion to the fixed portion . the fixed portion has a gas flow orifice and the movable portion is pivotally movable between 1 ) a relaxed position , below a specified operating pressure to establish a first gas washout flow area , and 2 ) a fully pressurized position . at or above the specified operating pressure , the pressurized gas pivots the movable portion adjacent the fixed portion to cover at least a portion of the gas flow orifice and establish a second gas washout flow area . the second gas washout flow area is less than the first gas washout flow area .