DEVICE FOR REPLACING THE FILTER OF A GAS MASK IN POLLUTED ATMOSPHERE WITHOUT ANY CONTAMINATION RISK

Abstract: Device for preventing the inflow of air into a gas mask during the substitution of its filter (1) in the presence of contaminated atmosphere. The device comprises a small plate (12) having a central stem (13) which passes through the support (9) of a check valve admitting air to the respiratory tracts and a spring (14) which pushes said small plate (12) against the diaphragm (7) of the check valve when the filter is removed from the mask.

Description: The present invention refers to a gas mask for the protection of the respiratory tracts and more precisely it concerns a device which, in said gas mask, is able to prevent the air inflow towards the user's respiratory tracts when the filter is removed, allowing consequently the substitution of the latter also in the presence of contaminated atmosphere. As known, a gas mask can be constituted by several parts, among which it mainly comprises a filter and a fitting to connect it to the mask. Substantially, said fitting comprises a nozzle for screwing the filter and, behind the nozzle, a chamber into which is conveyed the already filtered air. A check valve is positioned between the nozzle and the chamber; as known from DE-C-958903, it consists of a diaphragm of elastomeric material, whose flexion, originated by a depression, allows the air passage from the filter to the chamber situated behind the nozzle. It was noted that in many cases the mask's user has to face the unforeseen event that the filter is exhausted, this being due for instance to an activity carried out for a time longer than it was considered necessary beforehand. In these circumstances the user, remaining in condition of apnea and having available a new filter, might effect the various steps needed to replace the filter, namely : to remove the exhausted filter from the mask nozzle, to take a new filter from a pocket or from an appropriate container, and to screw it on the mask nozzle. As it can be easily understood, the above indicated steps, to be carried out according to an apparently regular sequence, might be influenced - in the practice - by the psychological condition of the operator, different for the various users, with consequent differentiated risks which might lead to a temporary interruption of the apnea, with partial inhalation of air and therefore of nexious substances highly harmful for the user's health. Also, it is to be considered that the need of replacing an exhausted filter with a new one has a considerable importance in the event of a wide contamination in open air, as for instance in proximity of chemical or nuclear plants in consequence of serious accidents, namely there where the time to reach the area of intervention from not contaminated zones and then to return to the base is approximately the same, and sometimes longer, than the average life of a filter. The possibility of associating to a mask a device which enables the user to remain a long time in a contaminated atmosphere, by interrupting the inflow of polluted air during the replacement of the filter, is therefore highly desirable in the present technique. Unfortunately, up to this time a satisfactory solution has not yet been found, since the problems to be solved are several and, inter alia, in contrast with one another. In fact, one problem is that of providing and performing a further element or device to be associated to the usual accessories for gas masks without however modifying the mask structure and shape already established in accordance with the law provisions in force. An optimum solution, moreover, must intercept the ways of air flow from the outside to the inside of the mask during the substitution of the filter without anyhow affecting the regular operation of said ways of air flow when the filter is inserted in the mask nozzle. Another problem is represented by the fact of having to add further parts to those already existing in a mask without giving rise, owing to the additional weight, to conditions of intolerance or weariness for the mask's user. It is an object of the present invention to provide a gas mask with a device which is able to interrupt the air inflow during the substitution of the filter, allowing therefore this operation to be carried out in a contaminated area, and which is devoid of all of the above cited disadvantages. Accordingly, the subject matter of the invention is a gas mask for protecting the respiratory tracts, which comprises a filter and a fitting to connect it to the mask, the fitting comprising on its turn a nozzle whose bottom wall is provided with an opening communicating with a rear chamber into which flows the already filtered air, said opening being adjusted by a check valve consisting of a diaphragm leaning on the inner surface of said bottom wall and sustained in its central part by a support, an annular sealing gasket, made of elastomeric material, being inserted between the filter and the bottom wall of the nozzle, the mask being characterized in that it comprises a device to interrupt the air inflow when the filter is removed, the device comprising a small plate provided with a central stem passing through the valve support in the space inside the nozzle and a spring, one end of which is associated to the bottom wall of the nozzle and the other end of which acts to push the small plate against the diaphragm of the check valve, the spring being compressed by the filter inserted in the nozzle to detach the small plate from the diaphragm. The present invention will be better understood from the following detailed description given only by way of nonlimiting example and made with reference to the figures of the attached sheets of drawings, in which: FIGURE 1 - shows in section a fitting for a gas mask and the relative filter; FIGURE 2 - shows in section the fitting of FIG.1,with the filter removed from the nozzle; FIGURE 3 - shows the fitting of a conventional mask, with the filter inserted in the nozzle; and FIGURE 4 - shows on the right an enlargement of FIG.1 and on the left an enlargement of FIG.2. The present invention will now be described with respect to a conventional gas mask of any type, comprising the peculiar accessories for protecting the respiratory tracts and more precisely (see FIG.1) a filter (1),threaded in its lower portion,and a fitting (2) to connect the filter to the mask and to allow the air inflow towards the user's respiratory tracts. Fitting (2) comprises a nozzle (3), threaded internally, whose bottom wall (4) is passed through by an opening (5) communicating with a rear chamber (6) into which enters the already filtered air. Opening (5), in order to allow or to interrupt the air inflow towards the respiratory tracts, is regulated by a check valve consisting in a diaphragm (7), made of elastomeric material, leaning on that surface (8) of chamber (6) which coincides with the nozzle bottom wall. Diaphragm (7) is sustained in its central part by a support (9), having the shape of a bushing, which is connected by spokes (not visible) to a ring (10), which on its turn is made fast with the inner surface which limits opening 5. An annular gasket (11) of elastomeric material is inserted between the lower edge of filter (1) and the bottom wall (4) of nozzle (3) in order to ensure a perfect seal between the filter and the nozzle bottom wall. The present mask comprises substantially a device able to interrupt the air inflow towards the user's respiratory tracts when the filter is disconnected,so as to allow the introduction of a new filter in the nozzle even in the presence of contaminated atmosphere. Said device comprises a small plate (12) provided with a central stem (13) passing through support (9) of the valve in the space inside the nozzle, and a spring (14) having one end (15) associated to a ring (10) integral with the nozzle and the opposite end (16) acting on stem (13) so as to push the small plate against the diaphragm of the check valve. In the preferred embodiment shown in FIGURES 1 and 2, the spring is of conical type; its greater base leans on ring (10) integral with the wall containing opening (5) and its vertex is in contact with and situated below, the stem head (17). In this embodiment the stem, through spokes (18), is connected to an annular element axially displaceable inside the nozzle. Still preferably, the annular element is constituted by the same sealing gasket made of elastomeric material and in this solution spokes (18) are embedded in the thickness of the elastomeric material forming the gasket. As it can be seen in FIG.1, filter (2), screwed inside nozzle (3), pushes inward, with its own lower circumferential edge, the annular gasket (11) which, through spokes (18), pushes inward stem (13), overoming the action of the conical spring (14). Owing to the stem displacement, the diaphragm moves away from the small plate (12) and is therefore free to inflect and to allow the passage of air already filtered consequent to any action of inhalation by the user. In all the possible solutions deriving from the inventive principle, the stem stroke can take different values provided that, in all the selected solutions, said stroke may ensure the absence of any mechanical inteference between the small plate and the diaphragm in condition of maximum flexion following to air inhalation. Accordingly, a feature of the invention is represented by a stem stroke greater than the free deflection of the radially outermost edge of the diaphragm subjected to depression on during the user's inhalation. In particular a preferred embodiment is that shown in FIG.1, in which the stem has such a stroke as to bring the small plate in abutment against surface (19) of chamber (6), which is opposite to opening (5) communicating with nozzle (3). Further, advantageously, the surface of the small plate is provided with a central slot (20) which fits with the shape of the diaphragm's central support and, correspondingly, surface (19) of chamber (6) comprises a slot (21) to receive the most protruding portion of the small plate, avoiding therefore to occupy a part of the chamber space ready for the free flow of the air inhaled by the user. A further feature of the invention is represented by the provision of a spring (14), whose outward thrust is equal to or greater than, the product obtained by multiplying the depression generated by an involuntary action of inhalation by part of the user by the diaphragm area. For example, indicating with 500 mm H₂O the depression originated by an involuntary inhalation by the user, and adopting for diaphragm (7) a diameter of 28 mm, the minimum thrust to compress the spring is only of 300 grams. In fact, when the filter is exhausted, it can be removed from nozzle (13) (FIG.2 and left half of FIG.4) without any risk for the user's health even in the presence of a contaminated atmosphere, and this because any involuntary inhalation action by the user does not allow any inflow of contaminated air towards his respiratory tracts owing to the thrust exerted by spring (14), with the consequent closure of the check valve by means of the small plate (12). Moreover, the presence of a device inside fitting (2), in addition to the elements already existing in the conventional fittings, leaves unaltered the passage of the air flow towards the respiratory tracts. This fact will clearly appear from a comparison between the solution of FIG.1 and the prior art shown in FIG.3. As it can be seen in FIG.1, the inhaled air passes into chamber (6) and flows towards the respiratory tracts without encountering obstacles,more or less as in the prior art, with the only exception of a small and irrelevant dimensional thickness represented by the small plate (12) abutting against surface (19) of chamber (6). Also, it will be appreciated that the addition of the present device to the conventional elements, in the fitting of a gas mask, may advantageously be effected without the need of other stiffening arrangements or structural modifications in the shape and size of the already known fittings. In fact spring (14), stem (13) and small plate (12) are perfectly contained inside nozzle (3) and chamber (6), whose dimensions are practically those of the fitting according to the prior art shown in FIG.3. Further, the thrust of spring (14), for example of 300 grams, excludes any effort or stress which may compromise the resistance of nozzle (3), which is usually sized for values of minimum tension of 50 Kg. It is also evident that spring (14), by its thrust, excludes any additional effort for the user during the screwing of the filter inside nozzle (3). For instance spring (14), which in FIG.1 and 2 is advantageously shown in conical shape, in order to collapse and to occupy a small space, might be cylindrical. Also, spokes (18), protruding from the head of stem (13), might be associated with an annular element other than the sealing gasket (11), as for instance a further annular element interfering with the inner surface of the end of the fitting. Alternatively to what is said above, stem (13) and spring (14) might be placed under compression by a central portion of the filter rather than from the lower edge of the latter.

Claims: A gas mask for protecting the respiratory tracts which comprises a filter (1) and a fitting (2) to connect it to the mask, the fitting comprising on its turn a nozzle (3) whose bottom wall (4) is provided with an opening (5) communicating with a rear chamber (6) into which flows the already filtered air, said opening (5) being adjusted by a check valve consisting of a diaphragm (7) leaning on the inner surface (8) of said bottom wall, and sustained in its central part by a support (9), an annular sealing gasket (11), made of elastomeric material, being inserted between the filter and the bottom wall of the nozzle, the mask being characterized in that it comprises a device to interrupt the air inflow when the filter is removed, the device comprising a small plate (12) provided with a central stem (13) passing through the valve support in the space inside the nozzle,and a spring (14), one end (15) of which is associated to the bottom wall of the nozzle, and the other end (16) of which acts to push the small plate against the diaphragm of the check valve, the spring being compressed by the filter inserted in the nozzle to detach the small plate from the diaphragm. A gas mask as in CLAIM 1, characterized in that said spring is conical. A gas mask as in CLAIMS 1 or 2, characterized in that the stem end is connected by spokes (18) to an annular element (11). A gas mask as in CLAIM 3, characterized in that said annular element is constituted by the same sealing gasket. A gas mask as in CLAIM 4, characterized in that the spokes are embedded in the elastomeric material forming the gasket. A gas mask as in any of the preceding CLAIMS, characterized in that, when the filter is inserted in the nozzle, the stroke of the small plate is greater than the deflection of the diaphragm edge subjected to depression. A gas mask as in CLAIM 1, characterized in that the small plate, after its stroke, abuts against surface (19) of chamber (6) which is opposite to opening (5) communicating with nozzle (3). A gas mask as in any of the preceding CLAIMS, characterized in that the thrust of the spring on the small plate is at least equal to the product obtained by multiplying the depression generated by an involuntary inhalation by the user by the diaphragm area.

Inventors: CAPPA, GIULIO, MOSCATELLI, ROMANO
Applicants: MINISTERO DELLA DIFESA DIREZIONE GENERALE A.M.A.T., PIRELLI S.P.A.
Application year: 1988
Main classification: A62B9
IPC codes: A62B9