Air guidance in respirators

Abstract

 To assist better airflow distribution within a respirator facepiece (1) having an air inlet (4,5) offset from its median plane (II-II), the air inlet has a cover (12) on it with an end wall (16) which is inclined at an acute angle (α) to the normal to the axis (0) of the inlet and which has an aperture (17) in it at one edge portion extending into a side wall (15). When the inlet and cover are circular in outline the cover may be rotatable on the inlet and indicia be provided to indicate desired setting(s).

Description

[0001] This invention relates to air guidance in respirators.

[0002] A protective respirator has a face piece covering the whole of the user's face. It is desired to use the inlet air drawn in by his breathing to pass over the inner surface of the eyepiece or eyepieces to prevent misting due to condensation. This has been a frequent feature of respirators in the past.

[0003] In our EP-A-87909 we proposed one solution which works well in a respirator where the air inlet is in either one of two apertures in the face peice which are symmetrically disposed off the median plane of the face piece and the outlet is on the median plane.

[0004] US-A-4595003 shows a respirator which is similar from that point of view and which has a deflector on the air inlet in use to deflect de-fogging air along the inside surface of the visor.

[0005] FR-A-591502 shows a scoop-like extension on a central air inlet, to direct air onto an eyepiece.

[0006] CH-A-466052 shows a central air inlet with an integral wall dividing the inlet area from the outlet area and guiding inlet air upwardly.

[0007] DE-A-958903 shows a bifurcated, tube-like, extension from a central air inlet leading separately to adjacent two eyepieces.

[0008] The present invention is concerned with another means of improving equality of air distribution across both sides of such a respirator and is of particular value when used in conjunction with a type of inner enclosure within the respirator known as an or inasal enclosure that is to say an entity which defines a separate inner volume of the respirator in the region of the nose and mouth of the wearer, contacting his face all the way round that region.

[0009] What is needed is a simple element which can be fitted to the air inlet, whichever side that might be, to give an initial direction to the air which is inhaled so that it will pass in the appropriate direction for it to assist a desired distribution of flow within the respirator, especially increased equality of the flows over the eyepiece or eyepieces at each side of the median line of the respirator.

[0010] In the present invention therefore we have devised a cap for placing over the air inlet of the respirator which is offset from the centre line of the respirator which cap has a circular periphery and a squat cylindrical side wall, one end of the cylinder being open and the other being closed by an end wall. The structure of the cap is symmetrical, that is to say, one side of one diametrical plane through the cap is the mirror image of the other side of that plane. The end wall has an aperture in it offset from the centre axis of the cylinder (but preferably maintaining symmetricality about the said diametrical plane) and the side wall has a cut­out portion continuous with at least part of the aperture in the end wall, the cut-out again being preferably symmetrical about the said diametrical plane. The side wall of the cap is adapted to be clipped over the internal part of a mount of the air intake of the respirator and for its said diametrical plane to be oriented in relation to the face piece of the respirator such that the aperture and the cut-out give the inflow of air from the air inlet an initial direction such as to assist the even flow of air onto the eyepiece at each median side of the respirator. Because the cap is a symmetrical object it can be used at an equal and opposite setting whichever side of the respirator the air inlet may have been chosen to have been placed (this in turn will usually depend on whether the wearer of the respirator is right-handed or left-handed).

[0011] A particular embodiment of the present invention will now be described with reference to the accompanying drawings wherein

Figure 1 is a rear elevation of a respirator that is to say looking into the back of the respirator,

Figure 2 is a section of the respirator on the median plane II-II of Figure 1,

Figure 3 is a back view of the guide cover,

Figure 4 is a section on the plane IV-IV of Figure 3, and

Figure 5 is a side view of the cover.

[0012] Looking first at Figure 1, we see the face piece 1 of a respirator with separate eyepieces 2 symmetrically on each side of the median plane II-II of the respirator. Two apertures 4,5 may alternatively be used according to choice by the user as an air intake aperture fitted with the appropriate canister the other aperture being blocked or being used for, for example, an auxiliary speech transmitter.

[0013] Across the median plane of the respirator is provided an air outlet and speech transmitter 6, to the inner face of which is mounted an orinasal enclosure 7 which will contact the face of the wearer to form a separate enclosure within the respirator defining a volume around the nose and mouth of the wearer. Ingress to that volume is through an aperture or apertures 8. In order to reach the wearer as he inhales the air must travel from whichever of the inlets 4 or 5 has been selected through the aperture 8 and is to be brought over the eyepieces 2 as it does so.

[0014] The enclosure means 7 is fitted with wings 9 which at their lateral edges engage the inner surface of the face peice so that they form channels between themselves and that face piece. There are two possibilities in the present type of respirator for transverse flow of air across the median plane. One occurs in a plenum below the chin of the user and the other in a gap defined at 10 under the nose part of the orinasal enclosure 7 and above the outlet valve and speech transmitter 6. When the present type of enclosure is fitted it is this passage 10 which principally serves for transfer of air across the median plane and to assist it in this passage and to direct air initially towards the entrance of that passage, a guide means will be fitted to whichever of the apertures 4 and 5 is used as the air inlet.

[0015] The upper edge of the wings 9 forms a choke for the flow of air whereby resistance through that choke is greater than the resistance through the passage 10. However the guidance effected by the cap about to be described assists in an initial equalisation of flow so that the choking effect may not be as great as would otherwise be needed; which might in turn have impeded the free flow of air to the user. Additionally or alternatively, the wings 9 may each have at least one channel at their lateral edges and running parallel to them. These form guidance ducts for assisting flow of air upward in the facepiece towards the outer corner regions of the eyepieces.

[0016] The guide means is a cover for the air inlet. An example of cover 12 is seen in Figures 3 and 4. It is a squat cylindrical cap, with a cylindrical side wall 13 the length of which varies from a minimum in the region 14 to a maximum in the region 15, these regions lying on a plane IV-IV in Figure 3 about which the cap forms a mirror image. The cylinder is closed by an end wall 16 which because of the varying height of the side wall 13 is inclined to the plane of the normal to the axis 0 of the cap by an acute angle . Preferred ratios for are 10°-12°, most preferably 10.5°. The end wall 16 contains an aperture 17 offset from the axis of the cylinder and continuing into a cut-out portion 18 in the region 15 of the side wall 13. Both the aperture 17 and cut-out 18 are symmetrical about the plane IV-IV.

[0017] The radial extent of the aperture 17 may advantageously be between one half and three quarters of the way in from the side wall; in the present example it is approximately two thirds. Its tangential (chorded) extent is preferably such as to subtend an angle of about 90-120° at the axis 0, more preferably about 110°, as shown. As can be seen the peripheral extent of the cut­out 18 is somewhat less than that of the aperture 17, subtending an angle of about 90° at the axis 0 in this example.

[0018] The cover is fitted to the air inlet 4 or 5 to be used by a snap fitting between an internal rib 20 on the side wall 13 and an external annular recess on a mounting ring 19 of the air inlet. When as here the wall 13 is cylindrical and the ring 19 annular the fitting may in principle be at any angle and the cap be rotatable about the axis of the inlet which then coincides with the axis 0 of the cap. The aperture 17,18 coupled also with the inclination (seen in cross section) of the end wall 16 give an initial guidance to air inhaled from an air inlet at, say, 4 as indicated in Figure 4 to cause both a deviation of that air flow from the axial as shown by the arrow A and also to direct that air flow angularly (rotationally) about the centre axis 0 of the cylinder. With a given type of insert 7 and the face peice 1 it will be found empirically what the best setting is for a cap in relation to the median plane when it is mounted on the air intake at 4 or 5, and the appropriate setting can be set or indicated by indicia such as pips 21 or by detents.

[0019] The cap is designed to direct airflow into the respirator but without any increase in inhalation resistance. It has been found that the shape in achieving this is crucial if turbulence and increased resistance is to be avoided. The important elements are the angle of the end face 16 and the size and shape of the aperture 17. The more that 16 is angled into the respirator the higher the airflow will be and the less will be the resistance. Indeed by so doing it is possible to achieve lower resistance figures than are possible without the cap. However, at this point the cap may become too intrusive. The more 16 is angled towards parallel to the plane of the free edge, the more the inhalation resistance is increased. A mean can be achieved empirically in each model of respirator so that there is neither gain nor increased resistance. If an optimum is not required a single design of cap can be used in a range of different respirators.

[0020] The upward positioning of the aperture 17 is important. Any condensation will become trapped in a sump 22 in the bottom of the cap and is prevented from leaking or escaping into the inhalation valve area. This is important as when being used in cold conditions the condensate could freeze and cause the inhalation valve operation to be impaired or even cease.

Claims

1. A respirator having a median plane and an air inlet (4,5) situated in a face peice (1) of the mask at one or other lateral side of that median plane, with a cover (12) over the air inlet (4,5), the cover including an end wall (16) which extends partially across the cross-section of the air inlet and is set at an acute angle (α) to the normal to the axis (0) of the air inlet, and an aperture (17) in the wall (16) at one edge portion thereof, whereby air drawn into the respirator through the inlet is deflected and guided by the end wall and the aperture therein, to achieve a desired distribution of air within the respirator.

2. A respirator according to claim 1 wherein the cover (12) has an essentially cylindrical side wall (13) of varying height and the aperture (17) extends (18) into the region of the side wall.

3. A respirator according to claim 1 or claim 2 wherein the aperture extends for approximately two thirds of the radial extent of the end wall.

4. A respirator according to any one of the preceding claims wherein the acute angle (α) is 10° to 12°.

5. A respirator according to any one of the preceding claims wherein the tangential (chordal) extent of the aperture is such as to subtend an angle of approximately 90 to 110° at the axis (0) of the inlet.

6. A respirator according to any one of the preceding claims wherein the cover (12) is circular in outline and engages around an annular margin (19) of the air inlet, with means (19,20) for permitting rotation of the cap relative to the inlet, about the axis of the inlet.

7. A respirator according to claim 6 wherein the cover and an adjacent portion of the respirator bear indicia indicating a preferred rotational setting of the cap.

8. A respirator according to any one of the preceding claims wherein the cover is a discrete and detachable cap (12) secured to the air inlet (4,5).

9. A respirator according to any one of the preceding claims which additionally has an orinasal enclosure (7), the air inlet (4,5) and cover (12) being outside that enclosure.

Drawing