GB2264648A

GB2264648A - Protective mask

Info

Publication number: GB2264648A
Application number: GB9303179A
Authority: GB
Inventors: Jyrki Hannu Veli Jaervinen
Original assignee: Kemira Oyj
Current assignee: Kemira Oyj
Priority date: 1992-03-02
Filing date: 1993-02-17
Publication date: 1993-09-08
Anticipated expiration: 2013-02-17
Also published as: GB9303179D0; FI96171C; SE505744C2; SE9300466L; GB2264648B; FI920939A; DE4305869A1; FI96171B; SE9300466D0; FI920939A0

Description

1 PROTECTIVE MASK 2264648 The present invention relates to a protective

mask such as comprises a thin membrane which transmits speech outside of the mask and an external perforated cover covering the membrane.

Protective masks are used as f ace shields and respirator masks in certain tasks such as welding as well as for military purposes. In order f or the mask not to prevent talking, it should not substantially decrease the audibility and intelligibility of the users speech. With this in mind, the masks are provided with thin, sound- transmitting membranes which are placed in a suitable location in the jacket of the mask. The membrane construction is provided by forming an opening in the jacket of the mask and fitting, into the opening, the membrane and the perforated cover which covers the membrane in a caselike manner. The opening is then sealed at the edges thereof in order to keep the mask gas-tight.

A drawback of the above construction used up to now is that it is difficult to assemble. In addition, some problems have occured when sealing the edges of the membrane.

The purpose of this invention is to provide a new and simpler solution which avoids said problems of assembly and sealing of the known masks. The invention is characterized in that the membrane is formed by a thinner part of rubber or similar elastic material of the jacket of the mask and that the mask comprises a rigid supporting member which supports the thinner part at the edges thereof.

When the thinner part which forms the membrane, according to the invention, is made of the same piece as the other parts of the jacket of the mask, the problems of sealing the edges of the membrane can be completely overcome. The supporting member surrounding the thinner part can provide the construction with necessary rigidity so that it is not prone to ruptures resulting from bending the mask, for instance. The supporting member is 2 preferably comprised of a separate part which requires no sealing and is therefore easy to fit in place. Preliminary tests have indicated that the mask construction according to the invention can work well in practice and transmit sounds as well as the known masks available in the market do, if not better.

In the mask according to the invention it is preferred to arrange the supporting member to serve as a tightener which stresses the thinner part. Even though the stressing of the thinner part is not necessary in the view of operation of the mask, a small stress in the order of a few percent is preferred, however, considering the acoustic properties of the reduction. This further makes it possible to adjust the above-mentioned properties. The stress can be provided simply by making the diameter of the supporting member slightly larger than the groove or detent surrounding the thinner part where the edges of the supporting member are fitted.

According to the invention the supporting membermay be formed by a rigid abutment ring placed around the thinner part, to which the separate shield covering the thinner part is secured by a snap-fastener. Alternatively said cover can be arranged to serve as a supporting member or a tightener, whereby said abutment ring is not required.

According to a preferred embodiment of the invention the thinner part is covered by two superimposed, essentially plate-likeshields which are f itted in such a way that the holes in them do not align. The advantage of this solution is that an object which possibly hits the mask and which permeates the hole in the outer shield can be stopped by the inner shield so that it cannot damage the membrane.

The optimum wall thickness of the thinner part which forms the membrane depends on the gas tightness and the sound transmission capability of the material used. A suitable wall thickness of butyl rubber is 0.5 to 1.5 mm, for instance, the wall thickness of the other parts of the jacket of the mask being preferably 4 3 between 2-3 m-m. Along with rubber, elastic plastic materials are suitable for the material of the jacket of the mask.

In the following the invention is described in more detail in an examplary way with reference to the appended drawings where:

Fig. 1 shows a protective mask according to the invention provided with a sound-transmitting membrane and a shield covering it, Fig. 2 shows the membrane according to an embodiment of the invention provided with an abutment ring and a shield covering the membrane, Fig. 3 is a section of another embodiment of the invention showing the membrane provided with an abutment ring and a shield, Fig. 4 is a section of an embodiment of the invention where the membrane is provided with a perforated, disc-like shield covering it, and Fig. 5 is a section of an embodiment of the invention, where the membrane is covered by two superimposed, plate-like shields.

Fig. 1 shows protective mask 1 where the main parts are jacket 2 of the mask covering the userfs face and membrane 3 with shield 4 placed in the jacket near the user's mouth. The purpose of the membrane is to transmit sound in such a way that the mask interferes with the audibility and intelligibility of its user's speech as little as possible.

A membrane construction according to the invention is presented in Fig. 2 in more detail. The membrane is formed by circular thinner part 3 which is integral to the jacket and provided in jacket 2 of the mask and surrounded by annular rib 5. Rib 5 forms an annular groove inside of jacket 2, having rigid abutment ring 6 fitted in it. If the dimension of abutment ring 6 is slightly wider than said groove, it serves as a tightener which slightly stresses thinner part 3. In addition, abutment ring 6 strengthens annular rib 5 surrounding the thinner part in such a way that the parts together form an abutment where shield 4 covering the thinner part is attached by a snap-fastener. Shield 4 is made sound-transmitting by providing it with holes 4 7. The sound-transmission of thinner part 3 is based on its vibration and can be effected on by the stress provided by abutment ring 6.

Jacket 2 of the mask can be made of rubber, f or instance, whereby the wall thickness of thinner part 3 is suitably between about 0.5-1.5 Tam, for instance, about 1.0 min, and the wall thickness of the parts of jacket 2 outside the thinner part about 2-3 mm, for instance, about 2 mm. Abutment ring 6 and shield 4-can be made of rigid plastics or metal, for instance.

The embodiment of the invention shown in Fig. 3 is largely like the one shown in Fig. 2. The only difference is that another annular rib 8 surrounds thinner part 3 outside shield 4 and that thinner part 3 projects somewhat from the level of the surrounding jacket 2.

The embodiments according to Figs. 4 and 5 differ from those in Figs. 2 and 3 in that shield 4 which covers thinner part 3 also serves as a supporting member, whereby internal abutment ring 6 of the thinner part can be omitted. In Fig. 4 shield 4 is provided by a fairly thick disc-like member which gives depth to holes 7 which penetrate the shield and improves the protection provided by them against random punctures. Reduction 3 is surrounded by ring groove 10 which is provided using annular shoulder 9 and has a flange which goes around shield 4 fitted into. By dimensioning shield 4 in a suitable way, it can serve as thetightener of thinner part 3.

In Fig. 5 two superimposed, essentially plate-like shields 11, 12 are substituted for disc-like shield 4 shown in Fig. 4, being so placed that their holes 7 do not align. This results in that objects hitting the holes of external shield 11 are stopped by inner shield 12 without damaging thinner part 3. The edges of shields 11 and 12 are superimposed in annular ring 10 formed around thinner part 3.

The intelligibility of speech transmitted through the membrane construction according to the invention was tested using the so- 2 called RASTI method (Bruel/Kjaer), where two gas masks according to the invention were compared with sixteen different masks available in the market, comprising conventional membrane constructions secured.to the opening in the jacket of the mask.

Mask M61 K1 according to the invention, where the thickness of the thinner part serving as the membrane was 1.2 mm, reached a RASTI value of 1.0 and mask M61 0.6, where the thickness of the thinner part serving as the membrane was 0.6 mm, reached a RASTI value of about 0.93. The values of other masks according to the known technique varied between about 0.62-0.95, the mean value being about 0. 85. The RASTI value measured without a mask was 0.91.

It will of course be understood that the invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention. For instance, the membrane with its shield need not necessarily be round, as other forms are possible as well. Also the location of the membrane in the jacket of the mask can differ from that illustrated in Fig. 1.

6

Claims

1. A protective mask comprising a thin membrane which transmits the speaking voice outside the mask, and an external perforated shield which covers the membrane, characterized in that the membrane isformedbya thinner part formed into the jacket of the mask which is made of rubber or similar elastic material and that the mask comprises a rigid supporting member which supports the thinner part at the edges thereof.

2. A protective mask according to claim 1, c h a r a c t e r i z e d in that the supporting member is arranged to serve as a tightener which stresses the thinner part.

3. A protective 'mask c h a r a c t e r i z e d according to Claim 1 or 2, in that the mask comprises a rigid abutment ring encircling the thinner part, where the shield covering the thinner part is secured using a snap-fastener.

A protective -mask according to Claim! 1 or 2, c h a r a c t e r i z e d in that the shield covering the thinner part is arranged to serve as a suppor-ing member or a tightener.

5. A protective mask according to Claim 4, char a cter i z ed inthatagroove surrounding the thinner part is formed in the jacket of the mask, the edges of the shield covering the thinner part being situated in the groove.

6. A protective mask according to any of the preceding Claims, char acteri zed in that the thinner part is covered by two superimposed and essentially plate-like shields which are so placed that the holes in them do not align.

7 7. A protective mask according to any of the preceding Claims, c h a r a c t e r i z e d in that the thinner part is essentially round.

8. A protective mask according to any of the preceding Claims, c h a r a c t e r i z e d in that the wall thickness of the thinner part is about 0.5-1.5 mm.

9. A protective mask according to any of the preceding Claims, c h a r a c t e r i z e d in that the wall thickness of the jacket of the mask. outside the thinner part is about 2-3 MM.

10. A protective mask substantially as herein described with reference to and as illustrated in Figures 1 and 2, 3, 4 or of the accompanying drawings.