MASK

Abstract: A mask assembly for allowing application of gases to the nose and/or mouth of a person, typically a hospital patient, which comprises a delivery nozzle (ll), a mask (l0) for coverng the nose and mouth of the patient and a retaining strap means (l2), all parts of the mask assembly being integrally moulded of the same substantially non-elastsic plastic material, the retaining strap means (l2) comprising a strap (l2) having a free end (l5) selectively connectable to the mask (l0) via a clip means (l4) in such a manner that the strap means (l2) is adjustable in length.

Description: The present invention relates to a mask preferably but not exclusively for medical use for administering gases such as oxygen or for use with a nebulizer. Hitherto masks have been widely used in medical practice for the application of gases or, more recently, for use with nebulization, that is the application of drugs to a patient by means of an aerosol produced by a flow of gas, the aerosol and drug being breathed in through a face mask. For hygienic reasons, it is preferred to use a new mask for each treatment. Thus masks have increasingly become considered to be disposable items. Hitherto, however, mask assemblies have comprised a face mask of generally plastics material, a separately formed nozzle for connecting to the supply of gas, and a retaining strap generally in the form of a separate woven elastic strap connected to the mask itself by various means including knots in the woven elastic and holes in the mask. Various configurations of face mask have been tried but they suffer from the disadvantage of being relatively costly items, and in particular generally being more costly than is desirable in a disposable item. In particular the cost of the mask is increased because the strap for holding the mask in contact with the face is a separately produced item and manual labour is required to assemble the strap and the mask whether the strap is connected to the mask simply by passing the strap through the hole in the mask and tying a knot there behind or by other clip means which typically comprise metal rings. An example of such a mask is disclosed in British Patent Specification 9202l6 in which the mask is retained to the patients face by means of tapes or elastic bands l5 which are attached at spaced points to the periphery of the mask and are then passed around the back of the patient's head. The mask in British Specification 9202l6 is intended to cover the nose and mouth of the patient and includes a gas delivery pipe ll in addition to the tapes l5. It will be understood that the mask comprises a number of other separate parts, the gas delivery pipe ll, the collar l9, the wire l4 and the skirt portion 2l. The applicants have also had drawn to their attention French specification 8482268 which shows a gas mask moulded in a resilient material (rubber). There are considerable difficulties in moulding rubber at high speed which is necessary if the mask is to be produced cheaply. Furthermore the moulding arrangement disclosed in the French Specification 848268 would not lend itself to moulding with a suitable modern plastics material. If a resilient elastic material such as rubber is used for a mask, then because of its resiliency it has to be of substantial thickness to be self supporting and able to maintain it's shape. In particular, the cup shape part covering the nose and mouth must be fairly thick to be sufficiently rigid to maintain it's shape when the patient breathes in. This is very wasteful of material and makes the mask very expensive. For this reason, a more rigid plastics material must be used which will maintain it's shape. Such a material is substantially non-elastic and it is therefore not possible to mould it in the way shown in the French patent specification. It is only by the use of such a material that a sufficiently rigid mask can be made which is of thin-wall section elastic. Furthermore, the mask in the French specification is incomplete requiring the addition of glass or other material for the eye holes. The present invention provides a mask assembly for allowing application of gases to the nose and/or mouth of a person, comprising a gas delivery nozzle, a mask for covering the nose and mouth of the person, and a retaining strap means, characterised in that all parts of the mask assembly are integrally moulded of the same substantially non-elastic plastics material, the retaining strap means comprises a strap having a free end selectively connectable to the mask via a clip means in such a manner that the strap means is adjustable in length. For the first time the invention provides a mask assembly the whole of which can be moulded in a single operation from a single plastics material which is usually flexible, but not very elastic and there is no requirement for separate insertion or attachment of strap means to hold the mask in place. The moulding of the mask assembly may thereby be carried out fully automatically by simply moulding the mask, for example, by injection moulding, in a single operation. Preferred arrangements of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure l is a perspective view of a first mask assembly according to the invention, Figure 2 is a perspective view of a second mask assembly incorporating a second embodiment of the invention, Figure 3 is a perspective view of a third mask assembly incorporating a third embodiment of the invention, Figure 4 is a side view of the mask assembly Figure 3, Figure 5 is an end view of the mask assembly of Figure 3, Figure 6 is a section of a nozzle part of the mask assembly of Figure 3, and, Figure 7 is a perspective view of part of the clip means of the mask assemby of Figure 3. Figure l illustrates a mask assembly comprising a one-­ piece injection moulding of plastics material (transparent, flexible, but substantially non-elastic polyvinyl chloride PVC moulded at l70-l80°). All of the parts illustrated are moulded of this plastic and no additional parts are necessary either during moulding (ie no separate metal clips etc are inserted in the mould before moulding) and no additional assembly work of clip parts or strap is necesary. The face mask assembly comprises a mask l0 incorporating a gas delivery nozzle ll, a strap l2 connected to one edge l3 of the mask l0, and a clip means l4 in two parts, one part l6 being formed at the free end of the strap l2 and the other part l7 being formed on an edge l8 of the face mask l0 opposite the edge l3 (although the part l7 could be formed on the free end of another strap attached to the mask). The mask l0 also includes exhaust apertures l9. Although the mask assembly is injection moulded in one operation of the same PVC material, the thickness of the material and cross-section varies to allow the different parts of the face mask assembly to carry out their normal function. Thus for example the face mask l0 is generally of relatively thin material (typically l.lmm) with a flexible thin sealing edge seal 2l surrounding the mask l0 for sealing engagement with the face of the patient. The cylindrical gas delivery nozzle ll is formed of a predetermined standard dimension so as to fit with standard products such as nebulizers or venturis (typically 22 mm outer diameter) with predetermined tapers to accord with international standards. The nozzle is arranged so as to direct the gas flow through the nozzle ll towards the nose of the person wearing the mask l0. The cross-section and width of the strap l2 is chosen so as to provide sufficient strength for the strap. To provide a variation in the length of the strap in use, the clip portion l6 comprises, at the end of the strap l2, a plurality of spaced male parts in the form of spheres 22 linked by links 23. The other part l7 of the clip forming the female part comprises a keyhole shaped slot 24 with which the spheres 22 and links 23 engage. Thus the effective length of the strap l2 (which is flexible but not elastic and therefore cannot be stretched to a desired length) can be adjusted by selecting the particular sphere/link combination to be engaged with the slot 24. Figure 2 illustrates an alternative arrangement of face mask assembly. The parts of Figure 2 are the same as in Figure l except for the clip l4. The male part l6 of the clip is the same as in Figure l but the female part, instead of being a keyhole shaped slot comprises a pair of sockets 26 part spherical with which two adjacent spheres 22 may engage. The sockets 26 are formed in resilient wall portions 27 which flex to allow insertion of the spheres into the sockets 26 and the flexible wall portions 27 then flex back to their normal position to clamp the spheres 22 in the sockets 26. Figures 3 to 7 show a third embodiment of the invention. The same reference numerals are used as with respect to Figures l and 2 for similar parts. The mask assembly is again a single one piece injection moulding of transparent flexible, but substantially non elastic polyvinyl chloride (PVC) which is moulded at a temperature of l70 to l80 C . The injection point for the injection of the plastic during the moulding is indicated at 50 in substantially the middle of the front face of the mask l0. The wall thickness of the mask l0 is, as before, approximately l.lmm except for the cross shaped region 5l delineated by dotted lines. Within this region 5l the thickness of the wall of the mask l0 is increased to substantially double that thickness, approximately 2mm. The thickened region 5l helps the mask l0 to maintain its shape and also allows, during moulding, plastic to more readily flow from the injection point 50 to other parts of the mould, and in particular the parts of the mould which form the strap means and the nozzle ll. The mask l0 of the mask assembly of Figure 3 is a somewhat different shape to that of Figures l and 2, as will be clear from the drawings. Furthermore, in this case the female part l7 of the clip means is attached to the mask l0 by means of a short length of strap 52. The form of the strap 52 is clear from the drawing and comprises a succession of transverse links 53. The transverse links 53 form a series of "X's" the ends of the links of which are joined together. Thus, although the material from which the mask assembly is manufactured is substantially non-elastic, the strap 52 is flexible and thereby forms an elasticated section 54 which can be resiliently expanded in length. This expansion takes place by bending of the transverse links 53 with respect to each other from the straight line form shown in the drawing to a curved form whereby the length of the strap 52 can be resiliently increased. Attached to the free end of this elasticated section 54 is the female clip part l7, the form of which is illustrated in the perspective view of Figure 7 and which is similar to the female part of the clip shown in Figure 2. It comprises two upstanding wall portions 27 each of which includes inwardly facing part spherical sockets 26. The wall portions 27 are connected to a base 59 in such a manner as to be slightly flexible away from one another. The strap l2 is connected, as with the arrangements of Figures l and 2, to one edge l3 of the mask l0, except that in this case it is connected by means of an elasticated section 6l similar to the elasticated section 54. Furthermore, the strap l2 is of circular cross section and includes at its free end, as before, a male part l6 in the form of spheres 22 linked by links 23. We will now describe the particular form of the nozzle ll in this case. The nozzle is arranged so as to be connectable to a multiplicity of different types of connectors. Thus, as described with regard to Figures l and 2, the outer diameter of the outer most wall of the nozzle 22mm. In addition, there is provided a central axial inner nozzle 62 having a standard outer diameter of 5.5mm and a chamfered free end 63 adapted to be connected with oxygen supply tubes. The inner nozzle 62 is connected to the outer wall of the nozzle ll by means of radial fingers 64 disposed at the inner end of the nozzle ll. The edge 2l of the face mask which engages the face of the patient wearing the mask is flexible so as to substantially seal with the patient's face. This can cause problems particularly as, during prolonged use, water tends to be trapped between this edge 2l and the skin of the patient's face. Accordingly, in the mask of Figure 3 (and the same technique can be applied to Figures l and 2) the part of the mould from which the surface of the edge 2l is moulded and hence the surface of the edge 2l is to be slightly rough. This prevents the close sealing of that surface with the patient's face and thereby prevent the trapping of liquid between that surface and the face and/or to allow the release of any liquids so trapped. This surface roughening of the part of the mould can be carried out in a number of ways, but the preferred method is to blast the surface with sand particles in a flow of gas, typically air (so called "vapour blasting"). The invention is not restricted to the details of the foregoing examples. For example the shape and disposition of the links in the elasticated sections 54,6l. The "X's" may be replaced by, for example, "O's" opening squares, "S's" or other shapes.

Claims: 1. A mask assembly for allowing application of gases to the nose and/or mouth of a person, comprising a gas delivery nozzle (ll), a mask (l0) for covering the nose and mouth of the person, and a retaining strap means (l2), characterised in that all parts of the mask assembly are integrally moulded of the same substantially non-elastic plastics material, the retaining strap means (l2) comprises a strap (l2) having a free end (l5) selectively connectable to the mask (l0) via a clip means (l4) in such a manner that the strap means (l2) is adjustable in length. 2. A mask assembly as claimed in claim l characterised in that the clip means (l4) comprises two parts, one part (22,23) attached to the strap (l2) and the other part (26,27) attached to the mask (l0). 3. A mask assembly as claimed in claim 2 characterised in that the two parts of the clip means (l4) include engaging portions, (22,26), one engaging portion (26) being a female portion and one engaging portion (22) being a male portion. 4. A mask assembly as claimed in claim 3 characterised in that there may be provided a plurality of either female or male engaging portions whereby selected engagement of male and female portions varies the effective length of the strap (l2). 5. A mask assembly as claimed in any of claims l to 4 characterised in that the gas delivery nozzle (ll) comprises a substantially cylindrical portion (ll) having predetermines and outer diameter and an internal nozzle (62) so as to be connectable to different connector assemblies. 6. A mask assembly as claimed in any of claims l to 7 characterised in that the gas deliver nozzle is arranged so as, in use, the axis of the delivery nozzle points to the nose of the person wearing the mask assembly. 7. A mask assembly as claimed in any of claims l to 6 characterised in that the strap means includes at least one part (54,6l) formed so as to be elastic. 8. A mask assembly as claimed in claim 7 characterised in that the or each elastic part (54,6l) comprises a plurality of transversely disposed links (23) extendig transversely to the length of the strap means, whereby said transversely extending parts (23) may flex to provide the required elasticity. 9. A mask assembly as claimed in any of claims l to 8 in which the mask has an edge portion (2l) abutting the face of the person, characterised in that said edge portion (2l) is formed with a rough surface to prevent the trapping of liquid between the mask and the face and/or to allow release of any liquid so trapped.

Inventors: BELLM, HOWARD GEOFFREY
Applicants: INTERSURGICAL (GUERNSEY) LIMITED
Application year: 1987
Main classification: A61M16
IPC codes: A61M16, A62B18