RESPIRATOR MASK WITH DETACHABLE SEAL

Abstract: A respirator having a faceseal which is detachable from the mask (10). The seal member (14, 22, 31, 41, 50) is accommodated in a pair of grooves defined by flaps (20, 43, 54) formed in the mask (10). Alternatively the flaps may be formed in a faces seal carrier (62), the arrangement being that the carrier can be bonded to the mask post forming. Ridges (23, 33) and corresponding grooves may assist in effecting the required seal. The arrangement permits using a profiled faceseal and maintaining the profile.

Description: RESPIRATOR MASK WITH DETACHABLE SEAL The present invention relates to respirators. It is particularly concerned with face-sealing respirators which comprise a facepiece for covering the face of a user and which are held in place by a harness which, in use, passes around the back of the wearer's head. The purpose of respirators of this type is principally to prevent the ingress into the user's respiratory system of toxic substances, particularly toxic fluids, especially gases, as well as particulate material. It is accordingly usually vital to ensure a good seal of the face mask part of the respirator to the user's face if one is not to adopt the more expensive measure of pumping clean air into the mask face cavity and thereby maintain a pressure therein greater than ambient. Known masks employ one of three measures to seal to the face. In the first of these the impermeable fabric of the face mask (usually a natural or synthetic rubber) is simply arranged to be soft and thin enough to locate against the skin. In the second of them the rim of the face mask incorporates a sealed airbag. In the third the rim incorporates a double skin re-entrant or reflex flap. With the first type, because the material of the sealing area must be at least the same thickness as the rest of the face mask, to ensure chemical resistance requirements are met, (2mm for natural rubber) the mask does not readily seal to all faces in the population, especially those with prominent or angular features. With the second type it is possible to employ as seal material a thin, soft rubber by comparison with the face mask, the material for which can then be relatively rigid. The sealed airbag will partially inflate during the inspiration phase of the breathing cycle, due to reduced pressure within the face mask. Thus the seal is the more effective when face seal leakage is the more likely to occur. There are two particular disadvantages associated with this second type of respirator. Firstly it is expensive to manufacture, necessitating hand building the seal to the face mask while both are in a partially cured state then final curing of this assembly. The process takes about 40 minutes. Secondly differential swelling of the rubbers takes place between those surfaces in and those surfaces not in contact with the user's skin. This leads to eventual stress cracking of the thin section seal profile and the consequent need to replace the whole respirator. With the third type a cost advantage is maintained in a respirator moulded of the one material. This however means that a compromise has to be made between the requirements for softness in the seal and rigidity in the face mask, since the face mask carries various sub-assembly units. For example, known respirators are provided which have a face sealing element enclosed within a rigid exoskeleton, such a mask consequently loses flexibility in order to provide sealing. In practice respirators of this third type do not achieve the same levels of protection across the whole population as those respirators with an airbag type faceseal. Similarly, many respirators currently available protect user's in an industrial environment by effectively prevent the ingress of airborne particulate material or potentially harmful vapours, such as those arising from an aerosol of solvent, but do not provide effective protection against the ingress of toxic gases or vapour, such as may be found in an emergency situation, for example in an accident in a chemical processing plant or in a military scenario. A respirator according to the present invention has a detachable face seal. Preferably, the face seal is flexible or resilient. It is an advantage of the respirator of the present invention over the prior art that the face seal is flexible or resilient and thus conforms in a sealing manner to the face of user while maintaining a high degree of comfort to the user, which is important if the respirator is to be worn for long periods. This not only enables the employment in the face seal of a material and dimensions thereof particularly suitable for sealing against a user's skin but also permits the use of a variety of face seal profiles with any one respirator. This in turn increases the range of people for whom any one respirator might be suitable and/or facilitates the full matching of particular respirators and users. There are fundamental conditions which respirators are normally required to meet. They must provide adequate protection across the population, male and female. The size which affords the necessary protection should also be the size in which the user's eyes align substantially with the horizontal centre line of the respirator eyepieces. In respirators according to the present invention these requirements are much more readily met than with the prior art respirators described above. In a preferred embodiment, a respirator in accordance with the invention incorporates a pair of parallel seal receptor grooves adapted to receive and to grip the edges of the face seal member. Preferably, the seal formed between the facepiece and the face seal member is fluid-tight. The grooves are preferably formed in a plane parallel locally with the mask profile. That groove relatively closer to the edge of the mask may be formed in a reentrant arrangement at the edge of the mask. The grooves may additionally be ribbed, for example in fir-tree pattern, to maximise both the contact area and hence the sealing surface area between the mask and the seal and also the gripping strength. Preferably, the seal between the user's face and the face seal is fluid-tight, thus preventing the ingress of toxic fluids into the respirator. In a preferred embodiment, the respirator is of the full facepiece type, which does not require the user to wear separate equipment for protection of the eyes. In the respirator art the words "mask", "facepiece" and "respirator" generally have particular meanings. Accordingly a mask is an as moulded rubber blank; a facepiece is a mask with all fixed sub assembly units attached, e.g. eyepieces, valve mounts, speech transmitter; and a respirator is a facepiece with a filter canister attached. These definitions are a general guide to the meanings of those words as used in this patent specification. The face seal member may typically be formed of a rubber material, preferably one of greater elasticity and flexibility than the material of the mask, and its general thickness may be between 0.5 and 2.0 mm, preferably 0.5 to 1.0 mm. However the invention also makes possible the use of a face seal member the cross section whereof contains an elastic foam material. In a preferred embodiment, the face seal member comprises a sac filled with a substantially fluid material. By the term substantially fluid material as used herein is intended a material which is sufficiently fluid to conform continually to the shape of the sac. More preferably, the fluid is a liquid or a gel, such as a silicone gel. Advantageously, the liquid used to fill the sac would not leak should the sac be damaged, for example ruptured or punctured. Ideally, the sac contains a liquid which sets in contact with air such that in the event of damage to the sac, the liquid will set, allowing the seal against the user's face to be maintained and hence providing the user with an improved degree of safety or at least time to remove himself from the likelihood of exposure to toxic substances. Where the face seal member is thus effectively a sac in cross section, the foam or gel containing integument may comprise a plastics membrane. In such cases the face seal member will preferably be constituted by a composite which also comprises flanges for inter-fitting groove members formed in the mask. Alternatively the mask may be formed with flange members, perhaps a pair of same disposed in parallel opposition, to receive and retain a sac cross sectioned face seal member. It may be advantageous, from the point of view of tooling and manufacture, for the grooves to be provided in a grooved member manufactured separately from the mask and attached thereto upon assembly of the facepiece. Respirators in accordance with the present invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a part-sectioned side elevation of a respirator facepiece in accordance with the invention; Figure 2 is a section of a facepiece edge in a first embodiment of the invention; Figure 3 is a section of a facepiece edge in a second embodiment of the invention; Figure 4 is a section of a facepiece edge in a third embodiment of the invention; Figure 5 is a section of a facepiece edge in a fourth embodiment of the invention; and Figure 6, 6a and 6b are sections of a facepiece in a fifth embodiment of the invention. The facepiece shewn in the drawings has a mask 10 incorporating eyepieces 11 and having a harness 12 whereby the respirator can be secured over the face of a user. Below the eyepieces and adjacent where in use the user's mouth will be is a manifold 13 for mounting a filter canister or for a connector to a clean air supply. Face seal means are located at the respirator edge as shewn at 14. One embodiment of a face seal arrangement in accordance with the invention is shewn in figure 2. The mask material has two re-entrant portions 20 adjacent its edge, whereby grooves are formed for retaining flanges 21 of a face seal member 22. There are abutment ridges 23 at the mouth of the grooves assist in retaining the face seal member 22. The mask 10 is moulded of a rubber material, formed with the re-entrant portions 20, and the ridges 23 in the moulding. The flanges 21 of the faceseal member 22 are profiled to locate in the re-entrant grooves formed in the mask body and are stepped to accept retention pressure from the ridges 23. The second embodiment of a face seal arrangement, shewn in figure 3, is similar to that shewn in figure 2 except that the face seal member 31 has fir- tree shaped ridges 33 arranged to interfit with opposing channels in the mask grooves. Both embodiments are illustrated with dotted lines demonstrating how face seals with a variety of profiles can be employed in the one respirator. In the embodiment illustrated in Figure 4, the face seal member comprises a sac 41 containing a flexible foam 42, the sac integument being of strong membrane dimensions and consistency. The mask has re-entrant portions 43 adjacent its edge, whereby a groove is formed for retaining flanges 44 formed in the face seal member. In the embodiment illustrated in Figure 5, the face seal member 50 comprises a backing strip 51 upon which is mounted a film 52. A sac is formed between the film 52 and the strip 51 and this contains a silicone gel 53. The mask has re-entrant portions 54 adjacent its edge, whereby grooves are formed for retaining the backing strip 51. In the embodiment illustrated in Figures 6, 6a and 6b, a mask 60 has an edge flange 61. A face seal carrier 62 comprises re-entrant flanges 63 and retaining ridges 64 as described above in relation to figure 1. It is adapted and arranged for bonding to the mask edge flange 61 , as shewn in Figure 6a. A face seal member 65, which may be of any of the above described types, is adapted for locating in the face seal carrier 62, as shewn in Figure 6b. In a typical example of a respirator according to the invention the mask 10 is moulded of chlorobutyl rubber 2 mm thick and of 60 Shore hardness. The skin to faceseal contact breadth is arranged to be at least 12 mm, by dint of the faceseal contour being smaller than that of the user's face. The seal cross section profile is accordingly tailored to take account of the fact that the forehead and chin regions will be the more affected by harness tension. In embodiments described with reference to figures 2 and 3 the achievement of the desired seal profile collapse may be assisted by varying the thickness of the seal across its section, for example 1.5 mm at the edges and tapering down to 0.J5 mm for 12 mm across the centre. The seal material may be natural rubber of 30 Shore hardness. The harness 12 is anchored to the facepiece body inboard of the edge thereof.

Claims: Claims 1. A respirator having a detachable faceseal member. 2. A respirator as claimed in claim 1 and wherein the face seal member has a moulded profile. 3. A respirator as claimed in claim 1 or claim 2 and wherein the face seal member comprises a relatively rigid backing strip to which is attached a relatively non-rigid membrane integument, a sac being formed therebetween. 4. A respirator as claimed in any one of claims 1 to 3 and wherein the face seal member comprises a sac containing a flexible material. 5. A respirator as claimed in claim 4 and wherein the sac contains a flexible material. 6. A respirator as claimed in claim 5 and wherein the flexible material is a plastics foam. 7. A respirator as claimed in claim 5 and wherein the flexible material is a gel. 8. A respirator as claimed in claim 7 and wherein the gel is a silicone gel. 9. A respirator as claimed in any one of the preceding claims and having a mask body incorporating a pair of parallel seal receptor grooves adapted to receive and grip the edges of a face seal member. 10. A respirator as claimed in claim 9 and wherein the grooves are formed in a plane parallel to that locally of the mask body. 11. A respirator as claimed in claim 9 or claim 10 and wherein a groove relatively closer the edge of the mask is formed in a re-entrant arrangement at the edge of the mask. 12. A respirator as claimed in any one of claims 1 to 8 and having a face seal carrier adapted for bonding to a respirator mask body, the face seal carrier incorporating a pair of parallel seal receptor grooves adapted to receive and grip the edges of a face seal member. 13. A respirator as claimed in any one of claims 9 to 12 and wherein the grooves are ribbed in an arrangement adapted to interfit with the face seal member. 14. A respirator substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: MATHERS WILLIAM GEORGE, MATHERS, WILLIAM, GEORGE
Applicants: MATHERS WILLIAM GEORGE, SECR DEFENCE, MATHERS, WILLIAM, GEORGE, THE SECRETARY OF STATE FOR DEFENCE
Application year: 1999
Main classification: A62B18
IPC codes: A62B18