referring initially to fig1 and 2 , there is generally indicated at 10 a respiratory mask including a shell or body portion 12 having an open side 14 that defines an annular surface 16 ( perhaps most clearly illustrated in fig3 ) to which is sealingly affixed a facial seal 18 constructed according to a first presently preferred embodiment of the instant invention . the mask body portion 12 is preferably , although not necessarily , a generally rigid formed structural shell , whereas facial seal 18 is a flexible , resilient unitary member which will be described in greater detail hereinafter . body portion 12 also defines an opening 20 to which there may be attached a fluid coupling means such as a swivel coupling 21 or other suitable means . the opening 20 and any intervening coupling means 21 connect mask 10 via conduit means ( represented by dashed line 22 ) to a source of gas 24 , e . g ., a blower of other suitable means for providing a flow of pressurized breathing gas , for administration of the gas to a user 26 . the mask shown is a nasal mask which accommodates the nasal regions of the user &# 39 ; s face . it is to be understood , however , that the invention also contemplates a full face or oral / nasal mask that accommodates both the mouth and nose of a user . as is conventional , mask shell 12 also preferably includes fastening means such as tabs 25 or the like to which may be connected suitable adjustable retention straps ( not illustrated ) for retaining the mask with respect to the user &# 39 ; s face . seal 18 includes a solid yet highly resilient and self - sustaining compressible annular member 27 comprising a peripheral wall portion 28 having an annular base or inner end 30 ( fig3 ) configured substantially similar to the annular surface 16 of shell 12 to which it may be fixedly attached . peripheral wall portion 28 further establishes an outer end 32 generally opposite inner end 30 . the outer end 32 defines a generally annular contoured sealing surface 34 adapted for confronting , sealing engagement with a user &# 39 ; s face . as will be more fully developed later herein , the contour of sealing surface 34 closely approximates the surface contour of a user &# 39 ; s facial structure in the areas of the bridge of the nose , the cheeks adjacent the nose , the space intermediate the nose and upper lip , and the intervening areas contiguous to these . for a full face mask ( not illustrated ) the sealing surface 34 would be contoured to accommodate the user &# 39 ; s chin in lieu of the area intermediate the nose and upper lip . in either case , variation in user facial structure , especially in the area of the bridge of the nose , for example , makes considerable seal flexibility necessary to accommodate the many different facial contours likely to be encountered . fig3 and 4 reveal in more detail the respiratory mask seal 18 . in accordance with the present invention , at least the seal or face - contacting portion or , more preferably ( as illustrated ), substantially the entirety of the annular member 27 is formed from a gel substance such as a viscoelastic polyurethane polymer possessing resilience or recoil characteristics corresponding substantially to those of human fat tissue . more specifically , the facial seal 18 including the annular member 27 preferably has a resiliency , as defined by durometer measured on the shore 00 scale which is used to gauge the resiliency of very soft resilient materials , of about 10 or softer and , most preferably , about 0 . such resiliency , corresponds substantially to that of human fat tissue which also exhibits a durometer reading of 0 on a shore 00 scale . in respect to the facial seal embodiment shown in fig1 through 4 , the durometer of facial seal 18 corresponds to the resultant durometers of the annular member 27 and its later described protective covering ( whose durometer is essentially negligible because of the thinness and pliability of the covering ). as for the facial seal illustrated in fig5 wherein the annular member 27 has no protective covering , the durometer of the facial seal is that of the annular member . although inherently capable of filling spatial voids , human fat tissue has negligible structural integrity and may not be self - sustaining . consequently , any respiratory mask facial seal possessing structural characteristics essentially identical to fat would be impractical from a usage standpoint . that is , if a facial seal were fabricated from a material structurally indistinguishable from human fat tissue in terms of resiliency , it may tend to sag into an amorphous shape under the influence of gravity and thus would not effectively conform to the contours of a user &# 39 ; s face even if headstrap tension was quite high . it will be appreciated , therefore , that a properly designed facial seal must substantially but not identically mimic human fat tissue from a structural , particularly resiliency , perspective . stated differently , the facial seal must exhibit some measurable recoil &# 34 ; memory &# 34 ; whereby it is structurally self - sustaining , capable of gently conforming to the topography of a user &# 39 ; s face under the influence of low headstrap tensile forces , resistant to distorting gravitational effects and self - restorable to its original configuration when removed from contact with the user &# 39 ; s face . the gel substance includes the property of recoiling back to substantially its original shape when not stressed . it must also be resistant to distortion due to positive gas pressure supplied to the mask . to simultaneously achieve these and other beneficial properties , the annular member 27 according to the present invention is preferably formed from a gel substance that , while virtually indistinguishible from human fat tissue when measured on the shore 00 scale , exhibits a resilency or durometer on the shore 000 scale ( which scale is used to measure the resiliency of extremely soft resilient materials ) of from about 20 to about 45 . by comparison , human fat tissue registers a durometer of about 10 on the shore 000 scale . the annular member 27 may be fabricated by conventional molding techniques . for example , liquid polyurethane polymer including any plasticizers and other modifiers necessary to achieve desired finished product properties is poured or injected into an appropriately configured mold . the polymer is then permitted to cure , either with or without the application of heat depending upon the specific composition and setting characteristics of the polymer , until the product achieves its desired solid gel form . because the polymer of the annular member does not have sufficient structural integrity to reliably adhere directly to the body portion 12 of the mask , the facial seal 18 also preferably comprises attachment means 36 which may be integrally molded into the inner end 30 of the annular member during its formation . attachment means 36 is desirably constructed as a substantially rigid annular ring having shape corresponding to that of the inner end 30 and a wall thickness less than or equal to that of the wall thickness of the peripheral wall portion 28 . at minimum , however , attachment means 36 should comprise a member less resilient than the gel substance of the annular member . to enhance bonding of the attachment means 36 to the annular member 27 , the attachment means desirably includes anchorage means 38 . the anchorage means may comprise spaced apart formations of the attachment means defining openings or similar structures into or around which the fluid polymer may flow and ultimately cure during formation of the annular member . annular member 27 also preferably comprises a plurality of integral bosses 42 molded into the peripheral wall portion 28 during formation of the annular member which extend from the inner end 30 toward the outer end 32 . bosses 42 provide gentle structural support to the annular member and promote uniform compression of the annular member when such member is in contact with a user &# 39 ; s face . the bosses are preferably symmetrically disposed about the peripheral wall portion and preferably correspond in number and location to the anchorage means 38 . as shown in fig3 a presently preferred construction includes five such bosses 42 corresponding to five anchorage means 38 . as previously mentioned , the presently preferred embodiment of facial seal 18 contemplates that the annular member 27 be covered by a protective covering . such covering means is identified by reference numeral 40 in the drawing figures . the covering means functions to increase the durability of the annular member while also permitting easy cleaning of the facial seal . covering means 40 must satisfy several physical criteria . it must , inter alia : ( 1 ) resist tearing and puncturing , ( 2 ) tightly conform to the annular member 27 without changing or deforming the contours thereof , ( 3 ) be chemically compatible with the annual member , ( 4 ) be biocompatible and non - irritating to a user &# 39 ; s skin , and ( 5 ) be sufficiently thin and supple such that its presence has a negligible impact on the resultant durometer of the facial seal 18 . in this regard , covering means 40 preferably comprises a thin ( approximately 2 to 10 mils thick ) flexible plastic film . urethane has been found to be preferable for this particular purpose as such material meets not only the objectives of the present invention but is also comparatively inexpensive and easy to apply to the surface of the annular member 27 . the covering means 40 may be applied to the annular member by any suitable process . for instance , liquid urethane may be applied by spraying or dipping and then permitted to cure . preferably , however , the urethane is prefabricated by vacuum forming so as to produce a skin of controllable and uniform thickness which is subsequently vacuum formed to the annular member using contentional techniques . once the facial seal 18 is fully assembled , it may be attached to the body portion 12 of a respiratory mask by coating the inner end 30 of the facial seal and / or the annular seating surface 16 of the mask body portion 12 with a suitable adhesive and then pressing the inner end 30 into abutment with the seating surface 16 whereupon the adhesive is allowed to cure . in fig5 wherein like references designate like or corresponding parts to those previously discussed , there is illustrated a further preferred embodiment of the facial seal of the present invention which is identified herein by reference numeral 118 . facial seal 118 differs from facial seal 18 essentially in that the annular member 27 thereof has no protective covering means on its outer surface . in all other material respects , facial seal 118 is constructed and functions substantially identically to facial seal 18 . the exposed surface of the annular member 27 of is tacky . as such , the inherent tackiness of the contoured sealing surface 34 of the annular member may thus be used to the user &# 39 ; s advantage by enhancing adhesion of the facial seal to the user &# 39 ; s face . in the alternative , if tackiness is not desired , the surface of the annular member 27 of facial seal 118 may be covered with a coating of powdered talc , silicone or similar biocompatible material . as presently contemplated , the wall thickness of the peripheral wall portion 28 of the annular seal member 27 of the facial seals 18 and 118 , excluding bosses 42 , preferably ranges from about 0 . 2 to 0 . 3 inches . the weight of the facial seals 18 , 118 depending on the size of mask bodies 12 with which they are used , ranges from about 1 to 2 ounces , a weight which has been discovered to be virtually unnoticeable to patients who have worn masks constructed according to the present invention in clinical tests . furthermore , the fat - like resiliency qualities of the gel material which forms the annular member 27 creates in the wearer a comparatively cool and natural tactile sensation when the facial seal is in contact with the user &# 39 ; s face . and , much like human fat tissue would perform , the facial seals 18 , 118 effectively fill gaps and mold to the user &# 39 ; s facial topography thereby minimizing leakage of gas supplied to the mask . indeed , experimental testing has shown that respiratory masks fitted with facial seals in accordance with the present invention exhibit minimal gas leaks with headstrap tensile forces of 3 pounds or less , a value substantially less than related masks presently known in the art . the facial seals described herein thus enable respiratory masks to be worn by users for prolonged periods with little or no measurable discomfort . this phenomenon is especially important to users who must wear respiratory masks for extended periods such as patients undergoing respiratory therapy . such individuals find that because of the comfort afforded by the facial seals 18 , 118 , their compliance with the respiratory treatment increases and the therapeutic benefits of the treatment are more fully realized . as an alternative to the embodiments discussed above , it is also contemplated that a respiratory mask of the present invention may be constructed as a one - piece member rather than as a separate facial seal joined to a mask body . in such case , the respiratory mask may be fabricated as a unitary member formed from substances of increasingly softer durometers , as considered in a direction from that portion of the mask corresponding to the mask body toward that portion corresponding to the facial seal , such that the softest materials , comprising the previously discussed gel substance and possessing the resiliency characteristics described hereinabove , would constitute the seal or face - contacting portion of the annular member . although the invention has been described in detail for the purpose of illustration , it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims .
an improved flexible respiratory mask facial seal , as well a respiratory mask incorporating such seal . the facial seal comprises an annular member including a peripheral sidewall bounded by an inner end and an outer end generally opposite the inner end . the inner end is adapted for attachment to the shell or body portion of a respiratory mask and the outer end defines a contoured sealing surface adapted for confronting sealing engagement with a user &# 39 ; s face . the annular member is formed of a gel substance possessing resilience characteristics corresponding to those of human fat tissue . preferably , the annular member is encapsulated in a thin , pliable , membranous covering to enhance the durability and washability of the facial seal . because the facial seal simulates the resiliency of human fat tissue , the user experiences the sensation of a natural substance against his skin when the mask is donned .