Water trap for respiratory airline

Abstract: A water trap for a respiratory airline comprises a top 10 and base 20 the respective openings of which mate when they are releasably connected e.g. by a bayonet-joint. The opening of the top 10 is partially spanned centrally by a disc 15, leaving an annular pathway for water around the periphery of the disc. A resilient annular sealing member 18 connected at its outer periphery to the top 10 makes sealing contact with the disc 15 when the base 20 is removed, but when the base 20 is connected to the top 10 the upper periphery 19 of the base raises the sealing member 18 to allow water to fall from top 10 and be collected in base 20.

Description: This invention relates to a water trap for a respiratory airline, and more particularly to a disposable water trap for respiratory and patient ventilation systems used to assist or promote breathing. In such airlines, used to conduct inhaled and exhaled gases to and from the patient, the problem of condensation and the collection in the airline of moisture which will obstruct it or even tend to drown the patient has been coped with for some years by the inclusion in the airline of a suitably positioned water trap in which the moisture will collect. This is essentially in two parts of which an upper has connections to the airline and the lower, releasably connects to the upper, takes the form of a water collection vessel. Normally the lower part is of a transparent or translucent material so that a nurse or other attendant can see when it is becoming full, disconnect it from the upper part, empty it and replace it. During this operation - ie: while the vessel or lower part is disconnected - the upper part must not be open to atmosphere since this would disrupt the treatment and might permit entry into the airline of ambient contaminants such as bacteria. Therefore it has been conventional that the opening of the upper part which normally mates with that of the vessel is controlled by a spring-loaded valve. One such example is disclosed in US Patent No. 4,951,661 in which on connection of the two parts the lower part upwardly displaces the valve stem of a spring-loaded valve disposed in the upper part so as to lift the valve from its seat and effect communication for drainage of the two parts. The inclusion of a metal spring increases the unit costs, which is undesirable in a disposable item. It is preferable that traps can be produced cheaply enough to avoid the need to sterilise a trap so that it can be used for another patient. On the other hand reduction of unit costs must not be at the expense of reliability, especially in the ability of the upper part to seal against atmosphere when the lower is disconnected. In US Patent No. 4,457,305 a cheap construction is disclosed in which in its disconnected state a valve member under the influence of gravity is urged against a valve seat thereby to seal the airline from atmosphere. The lower part is provided with an upwardly projecting valve lifter which during connection of the two parts lifts a valve from its seat. Although, simple in construction it lacks the reliability associated with traps comprising spring-loaded valves. Among the objects of the present invention are to provide a water trap in which the use of a metal spring is dispensed with and which may be made cheaply enough to be a disposable item. In accordance with the present invention there is provided a water trap for a respiratory airline comprising an upper component open at a bottom end thereof, a lower component in the form of a water collection vessel releasably connectable to the upper component, inlet and outlet connection means on the upper component for connection to the airline and means defining an upward opening of the lower component; it further comprises fixed disc means having a feed position centrally of said open bottom of the upper component and resilient sealing means in the region of the outer periphery of the upper component which, in an unstressed condition, will seal against said fixed disc means to close the bottom end of the upper component, the lower component having an upper periphery shaped so that when the upper and lower components are connected said upper periphery of said lower component will contact said resilient sealing means first to seal fluidtightly between said upper periphery and said resilient sealing means entirely about said upper periphery and then to displace said resilient sealing means upwardly, thereby to open the bottom of the upper component whereby a pathway will be provided for water to fall from the upper into the lower component only after said upper and lower components are fluidtightly sealed together. In a preferred construction said resilient sealing means comprises an annular resilient sealing member including an annular flap seal secured at its outer periphery in the region of the outer periphery of the upper component at a position such that, in an unstressed condition said annular flap seal will seal against said fixed disc means thereby to obturate said annular opening of the upper component, the lower component having an upper periphery shaped so that when the upper and lower components are connected said upper periphery of said lower component will press against and first seal fluidtightly between said upper periphery and said sealing member entirely about said upper periphery and then deform said sealing member upwardly to open said annular opening of the upper component whereby a pathway will be provided for water to fall from the upper into the lower component only after said upper and lower components are fluidtightly sealed together. The sealing member is preferably formed intermediate its inner and outer peripheries with a downwardly and outwardly extending annular projection, the upper periphery of the lower component being arranged to contact the sealing member on the radially inner side of said projection when the components are connected, the lower component being formed below and radially outwardly of said upper periphery thereof with a shoulder which will deform and sealingly engage said projection when the upper and lower components are connected, the arrangement being such that in the unstressed condition of the sealing member the projection is the lowest part of the sealing member and is therefore contacted by the shoulder before said upper periphery contacts the sealing member. The outer periphery of the sealing member is preferably engaged in a downardly-opening, annular recess on the radially inner side of the outer wall of the upper component, said wall being formed or provided below said recess with releasable connection means engageable with the lower component. Said recess preferably lies between said outer wall and an inner wall of the upper component and the sealing member preferably has intermediate its ends an upwardly extending annular projection which, in use, will lie adjacent the radially inner side of said inner wall, the arrangement being such that air pressure within the upper component will tend to form an air seal between said upward projection of the sealing member and the inner wall of the upper component. The sealing member preferably presents a concave annular surface inwardly and upwardly of the upper component between the upper extremity of the upward projection and the inner end of the sealing member. The outer periphery of the sealing member is preferably engaged in a downardly-opening, annular recess between the inner and outer walls of the upper component, the outer wall being formed or provided below said recess with releasable connection means engageable with the lower component. Said obtruction may be held in position in said opening of the upper component by tongues extending inwardly and downwardly of the upper component from positions intermediate the upper and lower ends of the latter. The releasable connection means is preferably a bayonet joint. An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional elevation of a water trap according to the invention shown in the assembled condition and taken on the line I-I of Figure 2, Figure 2 is sectional elevation taken on the line II-II of Figure 1, Figure 3 is a view similar to Figure 2 but showing the trap in the dis-assembled condition, and Figures 4 and 5 are details on an enlarged scale respectively of Figure 2 and of Figure 3 The water trap illustrated in Figures 1 - 3 comprises an upper component or top 10 and a lower component or base 20. The top 10 is formed with connections 13 and 14 whereby it may be included in known manner in an airline by pushing over the connections respective ends of flexible tubes (not shown). The top 10 terminates downwardly in a flared skirt 33 within which an annular wall 14 defines a downwardly-opening recess. The stepped configuration of the skirt 33 permits optional use of a hook (not shown) to hold the water trap upright. The hook has an upright flange which in use may be inserted into a slot (not shown) in the step of the skirt. The opening defined by the skirt 33 is spanned except at its periphery by a disc 15 the upper surface of which slopes downwardly at its periphery 16. The disc 15 is held in position centrally of the opening of the top 10 by two tongues 17 which extend downwardly and inwardly from the wall of the top 10 intermediate its upper and lower ends. Trapped in the recess defined by wall 14 is the outer periphery of an annular sealing member 18 of a resilient material such as natural rubber. As most clearly seen in Figure 4, in the unstressed condition of the sealing member 18 its inner periphery is urged into contact with the top of disc 15, thereby sealing the bottom opening of top 10. Intermediate its inner and outer peripheries the sealing member 18 has an upward projection 34 whereby an annlar groove 35 in the sealing member receives the wall 14. By this arrangement the projection 34 is pressed into contact with the radially inner side of wall 14 and the sealing member presents upwardly and inwardly of the top 10 a concave annular surface 36. By this arrangement any excess air pressure within top 10 will tend to press the projection 34 more closely into sealing enagagement with the wall 14 instead of allowing air to escape between the radially outer side of wall 14 and the main body of the sealing member. The base 20 is in the form of an upwardly open vessel which is preferably made from a transparant plastics material. Near to but not quite at its upper periphery 19 the base has a flange 21 and this and the skirt 33 have cooperating formations (not shown) providing a bayonet-type releasable connection between the top 10 and base 20. Bayonet connections are well known per se and will not be further described. As most clearly seen in Figures 4 and 5 the sealing member 18 is formed with an annular leg or projection 22 extending downwardly and outwardly therefrom. The projection 22 tapers to a knee-like formation 23 intermediate its ends which facilitates upward flexing of the distal portion of the projection. Between the flange 21 and its upper periphery 19 the base 20 has a shoulder 24 and the arrangement is such that as the base 20 is connected to the top 10 the shoulder 24 will raise the projection 22, forming a seal therewith. Moreover on its radially inner side at the junction with the sealing member 18 the projection 22 defines a notch 25. The upper periphery 19 of the base 20 contacts the sealing member on the radially inner side of this notch (Figure 5). As is again most clearly seen in Figures 4 and 5, as the upper end of the base 20 is received by the bottom opening of the top 10 and a bayonet connection is made the upper periphery 19 of the base raises the sealing member 18 so that its inner periphery rises from the disc 15. A pathway is thus provided for water to fall from the top 10 to be collected in the base 20. As soon as the base 20 is disconnected from the top 10, however, (Figures 3 and 4) for emptying this pathway is sealed as the inner periphery of the sealing member 18 comes beck into contact with the upper surface of the disc 15. The principal purpose of the projection 22 of the sealing member is to provide a temporary seal between the upper and lower parts of the trap before the base 20 is fully connected to the top 10. It will be evident that if the base 20 is approached to the top 10 at a slight angle to the coaxial the upper periphery 19 will tend to lift the sealing member 18 at one point on its circumference instead of uniformly all round. As a result a gap could momentarily appear between the sealing member 18 and disc 15 at a position where the periphery 19 is not in contact with the sealing member and this would permit entry into the water trap of ambient contaminants. To safeguard against this the projection 22, in the unstressed condition of the sealing member 18, extends downward sufficiently to be fully engaged all round by the shoulder 24, providing an air seal between the base 20 and top 10, before the upper periphery 19 contacts the main body of the sealing member 18. This can be ensured because the extent of possible misalignment is, of course, limited by the fact that the base 20 must enter the skirt 33 at the bottom of the top 10. The water trap described, having a small number of parts, can be produced cheaply and is suitable as a disposable item, i.e. it need not be used for more than one patient. Since it need not be sterilised e.g. by autoclaving for use by a different patient it is possible to use natural rubber for the sealing member 18. The properties of natural rubber are advantageous, but a synthetic such as neoprene would be indicated if the item had to undergo sterilisation. It will be evident that modification of the above embodiment is possible without departure from the scope of the appended claims. For example the disc 15 may be held in position by means other than the tongues 17. It is not essential that the pathway defined by the raised sealing member should be wholly annular if it is desired that web formations should extend between top 10 and disc 15, and if the pathway is of interrupted-annular configuration so could be the sealing member 18. The projection 22 and notch 25 of the sealing member are not essential. The connection between the top 10 and base 20 may if desired by a screw-threaded one. The connections 13 and 14 of the top 10 may take a variety of forms.

Claims: A water trap for a respiratory airline comprising: an upper component (10) open at a bottom end thereof, a lower component (20) in the form of a water collection vessel releasably connectable to the upper component (10), inlet and outlet connection means (13,14) on the upper component (10) for connection to the airline and means defining an upward opening of the lower component (20), characterised in that; it further comprises fixed disc means (15) having a fixed position centrally of said open bottom of the upper component (10) and resilient sealing means (18) in the region of the outer periphery of the upper component (10) which, in an unstressed condition, will seal against said fixed disc means (15) to close the bottom end of the upper component (10), the lower component (20) having an upper periphery (19) shaped so that when the upper and lower components (10,20) are connected said upper periphery (19) of said lower component (20) will contact said resilient sealing means (18) first to seal fluidtightly between said upper periphery (19) and said resilient sealing means (18) entirely about said upper periphery (19) and then to displace said resilient sealing means (18) upwardly, thereby to open the bottom of the upper component (10) whereby a pathway will be provided for water to fall from the upper into the lower component only after said upper and lower components are fluidtightly sealed together. A water trap in accordance with claim 1, characterised in that; said resilient sealing means comprises an annular resilient sealing member (18) including an annular flap seal (36) secured at its outer periphery in the region of the outer periphery of the upper component (10) at a position such that, in an unstressed condition said annular flap seal (36) will seal against said fixed disc means (15) thereby to obturate said annular opening of the upper component (10), the lower component (20) having an upper periphery (19) shaped so that when the upper and lower components (10,20) are connected said upper periphery (19) of said lower component (20) will press against and first seal fluidtightly between said upper periphery (19) and said sealing member (18) entirely about said upper periphery (19) and then deform said sealing member upwardly to open said annular opening of the upper component (10) whereby a pathway will be provided for water to fall from the upper into the lower component only after said upper and lower components (10,20) are fluidtightly sealed together. A water trap in accordance with claim 1 or claim 2, characterised in that; the sealing member (18) is formed intermediate its inner and outer peripheries with a downwardly and outwardly extending annular projection (22), the upper periphery (19) of the lower component (20) being arranged to contact the sealing member (18) on the radially inner side of said projection (22) when the components (10,20) are connected, the lower component (20) being formed below and radially outwardly of said upper periphery (19) thereof with a shoulder (24) which will deform and sealingly engage said projection (22) when the upper and lower components (10,20) are connected, the arrangement being such that in the unstressed condition of the sealing member (18) the projection (22) is the lowest part of the sealing member (18) and is therefore contacted by the shoulder (24) before said upper periphery (19) contacts the sealing member (18). A water trap in accordance with claim 2 or claim 3, characterised in that; the outer periphery of the sealing member is engaged in a downwardly-opening annular recess between the inner (14) and outer (33) walls of the upper component (10), the outer wall (33) being formed or provided below said recess with releasable connection means engageable with the lower component. A water trap in accordance with in claim 4, characterised in that; said recess lies between said outer wall (33) and an inner wall (14) of the upper component (10) and in that the sealing member (18) has intermediate its ends an upwardly extending annular projection (34) which, in use, will lie adjacent the radially inner side of said inner wall (14), the arrangement being such that air pressure within the upper component (10) will tend to form an air seal between said upward projection (34) of the sealing member (18) and the inner wall (14) of the upper component (10). A water trap in accordance with claim 5, characterised in that; the sealing member (18) presents a concave annular surface inwardly and upwardly of the upper component (10) between the upper extremity of the upward projection (34) and the inner extremity (36) of the sealing member. A water trap in accordance with any one of the preceding claims, characterised in that; said disc means (15) is held in position in said opening of the upper component (10) by tongues (17) extending inwardly and downwardly of the upper component (10) from positions intermediate the upper and lower ends of the latter. A water trap in accordance with any one of the preceding claims, characterised in that; the releasable connection means is a bayonet joint.

Inventors: HICKS RICHARD BANFIELD, HICKS, RICHARD BANFIELD
Applicants: INTERSURGICAL LTD, INTERSURGICAL LIMITED
Application year: 1991
Main classification: A61M16
IPC codes: F16L37, A61M16