GB2079160A - Filtering facepiece - Google Patents

Abstract

The facepiece is made from a flat pocket of filtering sheet material having opposed side walls 105, 106, a generally tapering shape with an open end 104 at the larger end and a closed, smaller end. The edge of the pocket at the closed end is outwardly bowed, e.g. defined by intersecting straight lines and/or curved lines, and the closed end is provided with fold lines 107 defining a surface which is folded inwardly of the closed end of the pocket to define a generally conical inwardly extending recess 108 for rigidifying the pocket against collapse against the face of the wearer on inhalation. <IMAGE>

Description

SPECIFICATION Improvements in and relating to respirators The present invention replates to improvements in respirators and particularly to filtering facepieces.

In co-pending Application No. 8009515 it is proposed to provide a filtering facepiece which is made from flexible filtering sheet material in the form of a flat pocket of generally frusto-conical sectional shape having an open edge at the larger end of the frusto-cone and a closed end at the smaller end of the frusto-cone. The closed end being defined by a straight line extending between the lateral edges of the pocket. The pocket is provided with fold lines defining a generally quadrilateral surface composed of two triangular surfaces having a common base extending in a direction generally perpendicular to the closed end of the pocket. The triangular surfaces are folded about the fold lines to extend inwardly of the pocket defining a generally V-shaped channel and so that they face each other and are, in use, relatively inclined to each other.

It has been found that, with such a filtering facepiece, the triangular surfaces have a tendency to unfold and revert to their original arrangement obviating the whole point of the triangular areas which is to rigidify the facepiece against collapse against the face of the wearer on inhalation and so that it automatically assumes a shape suitable to accommodate the face of the wearer.

It has now been found that a stronger and more stable arrangement can be produced in which the inwardly extending surfaces are so arranged as to have in effect an over-centre action when being folded to their inwardly extending position. In that position the surfaces define a generally conical recess in the closed end of the face piece, rather than the simple V-shaped channel of the facepiece of the above referred to co-pending Application.

Thus according to the present invention there is provided a filtering facepiece made from flexible filtering sheet material in the form of a flat pocket having opposed side walls, of generally tapering shape with an open end at the larger end of the pocket and a closed end at the smaller end of the pocket, wherein the edge of the flat pocket at the closed end is outwardly bowed and the closed end of the pocket is provided with first fold lines defining a surface which is folded inwardly of the pocket to define in use a generally conical recess extending inwardly of the pocket.

The closed, outwardly bowed, end of the flat pocket may have an edge which is defined by a curve, e.g. part of the circle, or by two or more intersecting straight lines so that it is generally conical, or by a combination of these two.

The closed end of the pocket may merge continuously or discontinuously with the lateral edges of the flat pocket. For example the side walls of the flat pocket may comprise a first portion providing the open end of the pocket which has the general shape of a section of a frusto-cone and a second portion which has the general shape of a section of a cone, the cone of the second portion having a larger cone angle than that of the first portion, the closed end of the pocket being provided by part or all of the second portion, alternatively the second portion may be generally arcuate, e.g. provided by a segment of a circle.

Preferably, the first portion providing the open end of the pocket has the shape of a section of a frusto-cone having a cone angle of about 600.

Preferably the surface defined by the first fold lines is a quadrilateral surface and is composed of two identical pairs of triangular surface portions each triangular surface portion having two adjacent sides common with other triangular surface portions, the pairs of triangular surface portions facing each other and being in use relatively inclined to each other and defining a generally pyramidical recess.

Advantageously the fold lines defining the quadrilateral surfaces are longitudinally rigidified and the fold lines defining the common sides of the triangular surface portions may also be longitudinally rigidified.

Such a filtering facepiece may be designed to be worn with one side wall overlying the nose of the wearer and with the other side wall underlying the chin of the wearer. With such an arrangement, the common sides of the identical pair of triangular surface portions extend in a generally vertical plane, and the fold lines defining these common sides on the one and the other side walls may be extended to the open edge of the pocket providing fold lines running along the crest of the nose and the centre line of the chin.

The one side wall may be provided with two further fold lines extending one from each lateral corner of the quadrilateral surface to the open edge of the pocket intermediate the centre and lateral extremity thereof to define a channel for receiving the nose of the wearer.

A deformable element may be provided extending along the edge of the one side wall between these further fold lines, the deformable element being initially bent to a generally U-shape and being intended to be shaped by the wearer to conform to the shape of the bridge of the nose of the wearer.

The filtering facepieces described above and hereafter are made from flexible filtering sheet material which may have particulate and/or gas or vapour filtering capabilities and may operate on the basis of mechanical and/or electrostatic and/or absorption and/or adsorption filtering of particles and/or molecules. For example, for particulate filtering, the material may comprise or be composed of fibres, typically cellulose fibres with added short glass fibres, or of giass fibres, made up into paper or a felt-like material, or microfibres having both electrostatic and mechanical efficiency and which may be made of P.V.C. or a polycarbonate, or an electret filter material. For gas or vapour filtering, the material may comprise or be composed of charcoal, for example in the form of cloth, or a charcoal impregnated material.

Such gas or vapour filtering material may be combined with a particulate filter material as required. The filtering material may be contained between two scrim sheets of low efficiency which play no effective part in the filtration.

The invention will be more fully understood from the following description of embodiments thereof given by way of example only, with reference to the accompanying drawings.

In the drawings: Figure 1 is a perspective view of an embodiment of a facepiece according to the present invention, in use; Figure 2 is a plan view from one side of a flat pocket for use in making the facepiece of Figure 1; Figure 3 is a plan view from the other side of the flat pocket of Figure 2; Figure 4 is a perspective view of a facepiece made from the pocket of Figures 2 and 3, at a stage in its production; Figure 5 is a side view of a facepiece made from the flat pocket of Figures 2 and 3 when in folded storage condition; and Figures 6 and 7 are plan views of flat pockets for other embodiments of facepieces according to the present invention.

The facepiece shown in Figure 1 is made from flexible filtering sheet material as descibed above and is initially in the form of a flat pocket 100, as shown in Figures 2 and 3, of generally tapering shape and having a closed end 101 at the smaller end of the pocket which has an outwardly bowed edge 102, closed lateral edges 103, and an open edge 104 at the larger end of the pocket. The facepiece is intended to be used with one side wall 105, hereafter called the upper wall, overlying the nose of the wearer and the other side wall 106, hereafter called the lower wall underlying the chin of the wearer, the closed lateral edges 103 extending along the sides of the face of the wearer.

A quadrilateral surface defined by fold lines 1 07a, 1 07b at the closed end of the flat pocket 100 is folded, as will be described hereafter, to create a generally conical, in fact pyramidical recess 108 extending inwardly of the pocket at the closed end thereof, the quadrilateral surface being composed on two pairs of substantially triangular surface portions 1 08a, 1 08b, each of which has two sides 1 09a, 1 09b, 1 09c in common, which face each other and which are, in use as shown in Figure 1, inclined to each other.

The fold lines defining the common sides 1 09c, are defined by the outwardly bowed edge 104 of the flat pocket.

The fold lines defining the common sides 1 09a, 1 09b, extend in use generally in a vertical plane and are generally perpendicular to the open edge of the pocket and on the plane of symmetry of the facepiece. Advantageously these fold lines are extended by fold lines 110 and 111 one on each wall of the pocket to the open edge 104 of the pocket. The fold lines 110 and 111 extend, in use, along the crest of the nose and under the chin of the wearer respectively.

In addition, the upper wall 105 of the facepiece may be provided with two further fold lines 112 each extending from a lateral extremity of the quadrilateral surface to the open edge 104 of the pocket intermediate the fold line 110 and the lateral edges 1 03 of the pocket. These fold lines 1 12 together with fold line 1 10 define in the upper wall 105 an inverted V-shaped channel 113 which seats on the nose of the wearer and positively adapts the upper wall 105 of the pocket to the shape of the wearer's face so as to decrease edge seal leakage around the nose and in the area between the nose and the cheeks.

The facepiece is held on the face by one or more head bands attached to the open edge of the pocket. As shown a single head band 114 is provided.

The production of a facepiece as described above will now be described in connection with filtering sheet material which is weldable, e.g. by high frequency, ultrasonic or heat, weiding. The facepiece is made from two blanks of the shape shown in Figures 1 and 2 which are welded together along the edges 102, 103 to create the closed pocket 100. Sealing welds may also be made along the edges of the open end 104 of the pocket to prevent fraying of the material along these edges.

Before, simultaneously with, or after the creation of the closed pocket 1 00, the fold lines 107,109 and 1 10 to 112 are defined. Some orall of these fold lines and the welds along the edges 102, 103 may be defined by welds which may be simple planar welds having a degree of longitudinal rigidity or welds which are profiled to increase the tendency of the material to fold along the weld and/or to increase the longitudinal rigidity of the fold line. Those fold lines which are not defined by welds may be defined by simple crease lines in the material. In a preferred embodiment fold lines 107 are defined by planar welds and fold lines 109 by profiled welds, fold lines 110 to 112 being defined by crease lines in the material.

To produce the facepiece shown in Figure 1 from the flat pocket 100, the pocket is opened by pulling on the ends M, N of the folds 110, 111 and at the same time the junction P of fold lines 1 09a and 1 09b at the closed end 101 is depressed to fold the pocket along the fold lines 1 07a, 1 07b defining the quadrilateral surface to create the inwardly extending conical recess 108 and the triangular surface portions 1 08a, 1 08b (Figure 4).

In depressing point P, which forms the apex of the conical recess 108, and forming the conical recess, it is seen that the quadrilateral surface in effect passes through an over-centre position so that in its final position it is resistant to unfolding and return to its original condition. Further separation of the points M and N brings the pairs of triangular surface portions together, as shown in Figure 5, and produces triangular wings 1 5 which are then folded about the fold lines 112 towards the point M to lie flat against the remainder of the pocket, as shown in Figure 5. At a convenient stage in production of the facepiece, the head band previously described is attached.

During production, a deformable strip 1 16 may be attached to the edge of the upper wall 105 of the facepiece so as to extend between the fold lines 112 over the fold line 110. When the facepiece is in its flat folded condition as shown in Figure 5, i.e. its normal storage condition, the strip 116 is bent double about fold line 1 10.

To use the facepiece, starting with the facepiece in its storage condition as shown in Figure 5, it is opened out by pulling apart the wings 11 5 to the condition shown in Figure 4. The upper wall 5 of the facepiece then automatically assumes the shape suitable for the wearer except that the strip 1 16 has to be opened out to open the channel 113 to receive the nose of the wearer.

The shaping of the upper wall 5 predisposes the facepiece to nestle into the difficult-to-seal areas to either side of the nose of the wearer and the strip 1 13 is, when the facepiece is on the face of the wearer, fitted to the shape of the nose of the wearer to improve the sealing across the bridge of the nose.

In the facepiece described with reference to Figures 1 to 5, the flat pocket of the facepiece has the general shape of a cone comprising a first portion providing the open end of the pocket which has the shape of a section of a frusto-cone, preferably having a cone angle of about 600, and a second portion which has the shape of a section of a cone, having a larger cone angle than that of the first portion. The closed end of the pocket is provided by part of the second portion so that the closed end edge 102 is outwardly bowed and defined by intersecting straight lines.As previously mentioned this has the effect, when the quadrilateral surface defined by the fold lines 107 is folded inwardly, of creating a generally conical recess 108 which, in being folded into the pocket in effect goes through an over-centre position so that it is securely recessed and does not have a tendency to revert to its original outwardly projecting position. This provides a considerably more stable facepiece than that of the above referred to co-pending Application and one which has therefore an increased resistance to collapse against the face on inhalation.

This effect can be obtained in other ways, by otherwise bowing the edge 102 of the closed end, for example as shown in Figure 6, where the closed end edge 102' is curved. In this embodiment the facepiece comprises a first portion providing the open end 104 of the pocket which has the shape of a section of a frusto-cone, as in the embodiment of Figures 2 and 3, and a second portion which is curved, for example has the shape of a segment of a circle, part of which forms the closed end of the pocket. With the pocket of Figure 6, by folding the closed end about the fold lines 107, a conical recess is again provided in the closed end of the pocket.

A further variation in the shaping of the pocket is shown in Figure 7, in which the pocket comprises three portions, the first of which, providing the open end 104 of the pocket, has the shape of a section of a frusto-cone, the second portion also has the shape of a section of a frustocone but with a larger cone angle than the first portion, and the third portion, providing the closed end edge 102" of the pocket has, as shown, the shape of a section of a cone, but may have the shape of a section of a frusto-cone, with a larger cone angle than that of the second portion.

It will be appreciated that the flat pocket of the facepiece may have a variety of other shapes than those described above provided that the edge of the open end included in the quadrilateral surface is outwardly bowed.

The angles included between the fold lines 1 07a and the fold lines 1 07b may be the same or, as shown, different. Preferably the angle between fold lines 1 07a is smaller than the angle between fold lines 1 07b. This has the effect of directing the apex P of the inwardly directed conical recess at the closed end of the pocket downwardly towards the chin of the wearer which better adapts the facepiece to the actual shape of the wearer's face and improves visibility for the wearer.

It has been found that there is an additional advantage in the face pieces described above in relation to that of the above referred to co-pending Application , in that the internal volume of the facepiece can be reduced while the area of the filtering material is maintained substantially constant. In effect more of the filtering material is included in the inverted cone at the closed end of the pocket so that material adjacent the cone can be cut away. An advantage of reducing the internal volume of the facepiece arises from the fact that the exhaled warm air which remains effect with such facepieces which results from the face that the exhaled warm air which remains inside the facepiece is subsequently inhaled with the apparent effect that the facepiece is warming the inhaled air.A reduction of the internal volume of the facepiece reduces the amount of exhaled air retained in the facepiece between exhalation and subsequent inhalation and therefore reduces the apparent warming effect. It will however be appreciated that for efficient filtering, the total surface area of filtering material in the facepiece must be maintained at a certain level so that reduction in the internal volume of the facepiece cannot be at the expense of the surface area. The facepiece described herein may include an edge seal as described in the above referred to copending Application As described above, the facepiece is made of weldable filtering material and is created by welding the material.Whether or not the material is weldable, the facepiece may be made up using other means, e.g. adhesive, and some or all of the fold lines may be defined either by preformed crease lines or for example by applying strips of plastics, e.g. by injection moulding or otherwise, along the fold lines, where these fold lines need to be longitudinally rigidified.

The facepiece described herein, as with the facepiece of the above referred to co-pending Application , can be regarded as comprising a frame defined by the fold lines 107, 109, 110 and 111, between which the filtration material extends. These fold lines can be likened to struts in compression which are pin jointed at their ends. The welds along the lateral edges 103 are under tension during exhalation and may be under compression during inhalation and therefore rigidity in compression is desirable. The strut formed by fold lines 109 is particularly important since this lends stiffness to the facepiece in a vertical position. The pin joints between the struts give the facepiece a degree of flexibility of mobility' so that it can easily adapt to fat or thin faces and can accommodate movement of the jaw of the wearer.

Claims (31)

1. A filtering facepiece made from flexible filtering sheet material in the form of a flat pocket having opposed side walls, of generally tapering shape, with an open end at the larger end of said pocket and a closed end at the smaller end of said pocket, wherein the edge of said pocket at said closed end is outwardly bowed and said closed end of said pocket is provided with first fold lines defining a surface which is folded inwardly of said pocket to define in use a generally conical recess extending inwardly of said pocket.

2. A facepiece as claimed in claim 1 , wherein said closed end edge of said pocket is defined at least in part by a curved line.

3. A facepiece as claimed in claim 2, wherein said curved line is an arc of a circle.

4. A facepiece as claimed in any one of the preceding claims, wherein said closed end edge of said pocket is at least in part defined by at least two intersecting straight lines.

5. A filtering facepiece as claimed in any one of claims 1 to 3, wherein said closed end edge of said pocket is defined by intersecting curved and straight lines.

6. A facepiece as claimed in any one of the preceding claims, wherein said side walls of said pocket comprise a first portion providing said open end of said pocket which has a generally frusto conical section shape and a second portion which has a generally conical section shape, the angle of the cone of said second portion being larger than that of said first portion and said closed end edge of said pocket being provided by at least part of the edge of said second portion.

7. A facepiece as claimed in any one of claims 1 to 5, wherein said side walls of said pocket comprises a first portion providing said open end of said pocket and which has a generally frusto conical section shape and a second portion having the shape of a segment of a circle, said closed end edge of said pocket being provided by at least part of the edge of said second portion.

8. A facepiece as claimed in any one of claims 1 to 5, wherein said side walls of said pocket comprise a first portion providing the open end of said pocket and having a generally frusto-conical section shape, a second portion having a generally frusto-conical section shape and a third portion having a generally conical section shape, the closed end edge of said pocket being provided by at least part of the edge of said third portion, and said cone angle of said third portion being larger than the cone angle of the frusto-cone of said second portion which is larger than the cone angle of the frusto-cone of said first portion.

9. A facepiece as claimed in any one of claims 6 to 8, wherein said frusto-cone of said first portion of said side walls of said pocket has a cone angle of 600.

10. A facepiece as claimed in any one of the preceding claims, wherein said surface defined by said first fold-lines in a quadrilateral surface which is provided with four fold lines which, in use, define a generally pyramidical recess extending inwardly of said pocket, said facepiece being adapted to cover the nose and mouth of the wearer with a pair of said four fold lines defining said pyramidical recess lying substantially in the plane including the nose and chin of the wearer, and means are provided for attaching the facepiece to the wearer's head.

1 A facepiece as claimed in claim 10, wherein said one pair of said four fold lines is longitudinally rigidified.

12. A facepiece as claimed in either claim 10 or claim 1 1, wherein said other pair of said four fold lines defining said pyramidical recess lie substantially in a plane perpendicular to said plane including the nose and chin of the wearer.

13. A facepiece as claimed in any one of claims 10 to 12, wherein said other pair of said four fold lines is longitudinally rigidified.

14. A facepiece as claimed in any one of the preceding claims, wherein said surface defined by said first fold line is a quadrilateral surface which is provided with fold lines defining two identical pairs of triangular surface portions, each triangular surface portion having two adjacent sides common with other triangular surface portions, the pairs of triangular surface portions facing each other and being, in use, relatively inclined to each other.

1 5. A facepiece as claimed in claim 14, wherein fold lines are provided in said quadrilateral surface defining said triangular surface portions, said fold lines extending along said closed end edge of said pocket and perpendicular thereto.

16. A facepiece as claimed in either claim 14 or claim 15, wherein said fold lines within said quadrilateral surface defining said triangular surface portions are longitudinally rigidified.

1 7. A facepiece as claimed in any one of the preceding claims, wherein said fold lines defining said quadrilateral surface are longitudinally rigidified.

18. A facepiece as claimed in any one of claims 11, 13, 16 or 17, wherein said sheet material is weldable and the or each said longitudinally rigidified fold line is provided by a weid in said sheet material.

19. A facepiece as claimed in any one of claims 11, 13, 1 6 or 17, wherein the or each said longitudinally rigidified fold line is provided by a rigidifying member affixed to said sheet material.

20. A facepiece as claimed in claim 19, wherein the or each said rigidifying member is made of plastics material.

21. A facepiece as claimed in any one of the preceding claims adapted for use with one side wall overlying the nose of the wearer and with the other side wall underlying the chin of the wearer, wherein a second fold line is provided in said one side wall extending from said surface defined by said first fold lines to said open edge of said pocket, said second fold line, in use, lying along the nose of the wearer.

22. A facepiece as claimed in claim 21, wherein a third fold line is provided in said other side wall extending from said first fold line defining said surface to the open edge of said pocket, said third fold line, in use, extending under the chin of the wearer.

23. A facepiece as claimed in either claim 21 or claim 22, wherein said second fold line of each of said second and third fold lines is, in use, substantially coplanar with one of said fold lines defining said triangular surface portions.

24. A facepiece as claimed in any one of claims 21 to 23, wherein fourth fold lines are provided in said one side wall extending from lateral extremities of said surface defined by said first fold lines to said open edge of said pocket on either side of said second fold line to define therewith a generally V-shaped channel for receiving the nose of the wearer.

25. A facepiese as claimed in any one of claims 21 to 24, wherein a deformable element is provided in the region of said open edge of said pocket and extending across said second fold line for engagement round the nose of the wearer, said deformable element being bent along said second fold line to a generally U-shape.

26. A facepiece as claimed in any one of claims 21 to 25, wherein said facepiece is initially folded flat with said side walls folded about said second and third fold lines to superimpose parts thereof and said one side wall is folded about said fourth fold line to superimpose parts thereof.

27. A facepiece as claimed in any one of the preceding claims, wherein said side walls are connected together along edges thereof extending from said first fold line to said open edge of said pocket and said connections are longitudinally rigidified.

28. A facepiece as claimed in any one of the preceding claims made from a flexible filtering sheet material which has particulate and/or gas or vapour filtering capabilities.

29. A facepiece as claimed in any one of the preceding claims made from filtering sheet material including microfibres having electrostatic and/or mechanical efficiency.

30. A facepiece as claimed in any one of the preceding claims made from filtering sheet material including activated charcoal.

31. A filtering facepiece substantially as herein described with reference to the accompanying drawings.