TECHNICAL FIELD

[0001] The present disclosure relates generally to air purifying respirators and more specifically to a method of manufacturing a filter unit for such a air purifying respirator. A filter unit for an air purifying respirator is also disclosed.

BACKGROUND

[0002] Air-purifying respirators are air filtering devices that protect against inhalation of both large and small particles by removing contaminants by filtration or absorption. They may be passive, APR, or powered, PAPR. The PAPRs have a great advantage over APRs, because they only require a simple fit test, and they do not increase the work of breathing. PAPRs also reduces the risk of leakage into the mask caused by growth of beard, wrinkles etc since they provide a positive pressure inside the face mask.

[0003] Air purifying respirators typically comprises a mask for covering the nose and mouth (half mask) or the entire face (full-face mask) of the wearer, a valve arrangement and a filter unit for purifying the inhalation air by filtering the air entering from the surrounding atmosphere into the mask.

[0004] The filter unit thus constitutes an important component of the air purifying respirator. Naturally the filter units should be capable of removing the dangerous or otherwise undesired particles from the inhalation air. Other desirable properties of the filter units are that they should be easily exchangeable, light and small in dimension not to impede the wearer, environmentally friendly and that they should allow quick manufacturing at low cost.

[0005] One type of previously known filter units comprises a comparatively thin sheet of a filtering media which has been pleated to form an accordion-like filter insert which is inserted into and sealingly attached to the interior walls of a filter housing having an air inlet and an air outlet. Another type of known filter units comprises a comparatively thicker felt-like filter material, one or several layers of which is inserted into a filter housing and sealingly attached to the inner walls. SUMMARY

[0006] An object of the disclosure is to provide an enhanced method of manufacturing a filter unit for an air purifying respirator.

[0007] Another object is to provide such a method which allows manufacturing of the filter unit at high speed and low cost.

[0008] A further object is to provide such a method which allows for a modular manufacturing whereby the total filter area of the filter unit may easily be varied.

[0009] Still another object is to provide an such a method which allows simple recycling of the filter unit after use.

[0010] Yet another object is to provide an enhanced filter unit for an air purifying respirator.

[0011] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0012] According to a first aspect, the present disclosure provides a method of manufacturing a filter unit for an air purifying respirator as defined in the appended claim 1. The method comprises the steps of;

- providing a sheet of filter material

- feeding a portion of the filter material to an open mould of an injection moulding machine

- closing the mould to thereby cut out a filter wall from the sheet

- holding the filter wall in said mould

- forming a filter panel frame around the filter wall by injection moulding a polymer material onto the filter wall

- opening the mould and

- retrieving a filter panel comprising the filter wall and the filter panel frame fixed to the filter wall. [0013] The method thus allows for that a filter panel which forms part of the filter unit may readily be produced at a single operation station in a combined filter material cutting and filter panel frame injection moulding operation. This reduces the need for intermediate handling and storage of the constituent components. The method also allows for high manufacturing speeds at low cost. The operation station preferably comprises a mould formed of at least two mould halves or members which are movable in relation to each other for opening and closing the mould. At least one of the mould halves or members comprises a cutting tool arranged to cut out the filter wall from the filter material sheet when the mould closes.

[0014] Additionally, the method also allows for a modular manufacturing process and a corresponding modular construction of the filter unit. This since the method allows for that any number of identical filter panels achieved by the method may be stacked together when forming the final filter unit. By this means, the total filter area of the filter unit may readily be adapted to various demands.

[0015] At some embodiments, the filter material and the injected polymer material comprise the same polymer material. This allows for that the filter frame is bonded to the filter wall by material fusion during the injection moulding. Additionally, this facilitates recycling of the filter panel since the entire panel may be recycled as a unit without the need of separating the filter wall from the filter panel frame.

[0016] Said same polymer material may be PP (Polypropylene) or PA (Polyamide).

[0017] The method may comprise repeating said steps for forming a plurality of filter panels.

[0018] Alternatively or in combination, the step of closing the mould to cut out a filter wall may comprise simultaneously cutting out a plurality of filter walls and the step of forming a filter panel may comprise simultaneously forming a number of filter panels, which number corresponds to the plurality of filter walls.

[0019] The method may further comprise the steps of; providing an inlet wall panel and an outlet wall panel; stacking the plurality of filter panels, the inlet wall panel and the outlet wall panel such that the plurality of filter panels are stacked between the inlet wall panel and the outlet wall panel. By this means the entire filter unit comprising an inlet wall panel, an outlet wall panel and any desired number of intermediate filter panels may readily be manufactured.

[0020] The inlet wall panel and the outlet wall panel may be produced by injection moulding of a suitable material. Preferably, the inlet wall panel and the outlet wall panel comprises the same material as the filter panel or filter panels of the filter unit. By this means recycling of the entire filter unit is facilitated. Additionally using the same material allows for that the panels are sealingly bonded together by material fusion for forming a sealed filter unit.

[0021] The method may comprise sealingly joining the peripheral edges of the filter panels, the inlet wall panel and the outlet wall panel. This allows for that the filter unit comprising the inlet panel, the outlet panel and the intermediate filter panel or panels may be connected directly to the air purifying respirator without the need of being received in or sealingly attached to any air tight housing or similar additional component for preventing surrounding air from being mixed with the filtered air flow in the filter unit.

[0022] Said peripheral edges may be sealingly joined by adhesion, heat fusion, ultrasonic welding, or by means of mechanical engagement means.

[0023] According to a second aspect, the disclosure provides a filter unit for an air purifying respirator as defined in appended claim 9. The filter unit comprises;

- an inlet wall panel having an air inlet opening

- an outlet wall panel having an air outlet opening and

- a plurality of filter panels, each filter panel having a filter wall and an air through passage, wherein said panels are sealingly stacked together to form a stack of panels in which the filter panels are arranged between the inlet wall panel and the outlet wall panel, which stack defines an interior air passage from the air inlet opening, through the filter walls and the air through passages to the outlet opening, which interior air passage is sealed from the outside of the stack.

[0024] At embodiments of the filter unit, said panels are planar.

[0025] Each panel may comprise a peripheral sealing portion which extends along the peripheiy of the panel and which is arranged to make sealing contact with a corresponding peripheral sealing portion of an adjacent panel. [0026] Each filter panel may comprise an interior sealing portion which extends around the air through passage and is arranged to make sealing contact with a corresponding interior sealing portion of an adjacent filter panel.

[0027] Each filter panel may comprise a peripheral frame surrounding the filter wall.

[0028] The filter walls and the filter frames may comprise the same polymer material.

[0029] The filter panels, the inlet wall panel and the outlet wall panel may comprise the same polymer material.

[0030] Further objects and advantages of the method and the full-face mask appear from the following description of embodiments and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

[0032] Fig. 1 is a section view schematically illustrating a step of an embodiment of the method of manufacturing a filter unit.

[0033] Figs. 2a and 2b are perspective views from different angles of a filter unit manufactured by an embodiment of the method.

[0034] Figs. 3a and 3b are exploded views in perspective from different angles of the filter unit shown in figs. 2a and 2b.

DETAILED DESCRIPTION

[0035] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0036] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description. [0037] Fig- 1 illustrates schematically a manufacturing station and a step of the method of manufacturing according to an embodiment. The manufacturing station comprises an injection moulding machine 10, having a first mould half 11 and a second mould half 12 which is movable in and out of engagement with the first mould half 11. The first mould half 11 has a mould cavity 11a and the second mould half 12 has a corresponding geometry 12a for forming, together with the cavity 11a, a space defining the shape of the filter panel (not shown in fig 1) to be manufactured. In addition, the second mould half comprises a cutting tool 13. In the shown example the cutting tool 13 comprises a knife. The cutting tool may however comprise other means for cutting out or severing a filter wall from a sheet 20 of filter material. Such other means may comprise punching means, heat severing means and the like. The cutting tool may be arranged in either of the mould halves or may comprise two or more cooperating tools arranged in both tool halves. The cutting tool 13 has a shape which corresponds to the peripheral shape of the filter wall to be cut out.

[0038] A supply roll 21 of sheet-formed filter material is arranged to supply the sheet 20 of filter material between the first 11 and second 12 mould halves when the mould is open. The free end of the filter material sheet 20 is received on a collection roll 22. The supply roll and the collection roll 22 are arranged to keep the sheet stretched or tensioned during the cutting operation. The filter material may comprise various different materials having filtering properties. At the shown example the sheet comprises nonwoven fibres of PP. However, other examples of suitable filter materials comprise PTFE (Polytetrafluoroethylene) and PA (Polyamide).

[0039] At the shown exemplifying embodiment of the method of manufacturing a filter unit, the sheet 20 of filter material is fed between the first 11 and second 12 mould halves when the mould is open. Thereafter, the mould is closed whereby the cutting tool 13 cuts out a portion of the filter material. The cut-out portion of the filter material is held in place in the mould cavity 11a by a clamping action exerted by the cooperating first 11 and second 12 mould halves. Alternatively or in combination, the mould may be provided with separate clamping means (not shown) for holding the cut-out portion of the filter material in the mould cavity 11b. While keeping the mould closed and holding the cut-out portion of the filter material in the mould cavity 11a, a polymer material is injected into the mould cavity 11a through a channel 11b arranged in the first mould half 11. The injected polymer material maybe selected from a wide range of thermoformable polymers. Preferably, the injected material should be fusible with the filter material such that the injected material is securely fixed to the filter material when forming the filter panel. The injected material may e.g. comprise the same polymer material as the filter material. In the shown example both the filter material and the injected material comprises PP. At a non-shown alternative both the filter material and the injected material comprises PA.

[0040] The mould cavity 11a is formed such that the injected material, when hardened, forms a rigid frame around the cut-out portion of the filter material, which frame is fixed to the filter material. When the injected material has hardened, the mould is opened and the filter panel comprising the filter wall and the filter frame fixed thereto is removed from the mould cavity 11a.

[0041] At a not shown alternative, the first mould half comprises a plurality of mould cavities and the second mould half a corresponding number of corresponding geometries as well as a corresponding number of cutting tools. At such embodiments, the filter material sheet is fed in between the mould halves such that it overlaps all mould cavities. Such embodiments allow for that several filter panels are produced at each injection cycle of the injection moulding machine.

[0042] For completing the filter unit, an inlet wall panel and an outlet wall panel maybe produced by injection moulding in a separate injection moulding machine. Alternatively, the inlet and/or the outlet wall panels maybe injection moulded simultaneously with the filter panel or filter panels in the same injection moulding machine. Since the inlet and outlet wall panels normally does not comprise any filter material, the mould cavities for forming these panels need not to be covered by filter material when the mould is closed.

[0043] At a further not shown alternative, the mould halves may comprise a mould cavity and a corresponding mould geometry for forming one or several filter panels, an inlet wall panel and an outlet wall panel which panels are formed as one integral piece with pairs of panels being mutually interconnected by a respective bridging portion. The bridging portion may act as a hinge such that the panels maybe folded in a zig-zag configuration to form a stack of panels with one or several filter panels being arranged between the inlet wall panel and the outlet wall panel. [0044] After having provided the filter panels, the inlet wall panel and the outlet wall panel in either way described above, the panels are stacked one on top of the other with the filter panel or panels being arranged between the inlet wall panel and the outlet wall panel. Thereafter, the peripheral edges of the panels are sealingly joined together such that the interior of the filter unit comprising the stack of panels is sealed-off from the surrounding atmosphere. This may be accomplished by means of mechanical engagement means which clamp the stacked panels mutually into sealing contact. Alternatively or in combination, the edges of the panels may be mutually] oined by adhesion, heat fusion and/or ultrasonic welding.

[0045] By this means, a filter unit is readily manufactured in a fast and costefficient manner. The resulting filter unit may be directly attached to the mask of an air purifying respirator without the need of any additional filter housing.

[0046] Figs 2a and 2b show an exemplifying filter unit 100 when assembled in respective perspective views. Figs 3a and 3b show the filter unit 100 in respective perspective exploded views.

[0047] The filter unit 100 comprises a first filter panel 110, a second filter panel

120, an inlet wall panel 130 and an outlet wall panel 140 which are stacked together with the filter panels no, 120 arranged between the inlet wall panel 130 and the outlet wall panel 140.

[0048] Both filter panels no, 120 are manufactured as described above and comprises a filter panel frame 111, 121 and a filter wall 112, 122 which filter wall is made of an air permeable filter material, and is surrounded by the filter frame 111,

121. Each filter frame 111, 121 exhibits two peripheral sealing portions 111a, nib, 121a, 121b facing in opposite directions.

[0049] The inlet wall panel 130 and the outlet wall panel are generally impermeable for air except at an inlet opening 135 and an outlet opening 145 respectively. Each of the inlet wall panel 130 and the outlet wall panel 140 comprises a peripheral sealing portion 131, 141 which faces the adjacent filter panel 110, 120).

[0050] When stacked, the peripheral sealing portion 131 of the inlet wall panel sealingly contacts the upper peripheral sealing portion 111a of the first filter panel no. Correspondingly the lower peripheral sealing portion mb of the first filter panel no sealingly contacts the upper peripheral sealing portion 121a of the second filter panel 120 and the lower peripheral sealing portion 121b of the second filter panel sealingly contacts the peripheral sealing portion 141 of the outlet wall panel 140. By this means the interior of the filter unit too is sealed from the surrounding atmosphere except at the inlet opening 135 and the outlet opening 145.

[0051] Both filter panels 110, 120 further exhibit a first air through passage 113, 123 surrounded by mutually cooperating first sealing rims 114, 124. The first filter panel 110 being arranged adjacent the inlet wall panel 130 further exhibits a second air through passage 115 which is aligned with inlet opening 135 arranged in the inlet wall panel 130. The second 115 air through opening and the inlet opening 135 are surrounded by respective and mutually cooperating second sealing rims 116, 136.

[0052] In figs 2a-3b the flow of unfiltered air is represented by solid arrows and the flow of filtered air is represented by dashed arrows. When the filter panels, 110, 120, the inlet wall panel 130 and the outlet wall panel 140 have been stacked and sealed as described above, air from the surrounding passes into the filter unit too through the inlet opening 135 in the inlet wall panel and continues through the second through opening 115 in the first filter panel 110. The unfiltered inlet air flow is prevented from entering the space between the inlet wall panel 130 and the first filter panel 110 by the cooperating sealing rims 116, 136. After having passed the second through opening 115 in the first filter panel 110, the unfiltered flow is divided into a first flow which passes through the filter wall 112 of the first filter panel and a second flowthrough the filter wall 122 of the second filter panel 120. The unfiltered air flow is prevented from entering the first air through passages 113. 123 by the cooperating first sealing rims 114, 124.

[0053] The air flow passing through the filter wall 112 of the first filter panel is filtered at this passage through the filter wall 112 and enters the space between the first filter panel 110 and the inlet wall panel 130. From this space the filtered air passes through the first air through passages 113, 123 and enters the space between the second filter panel 120 and the outlet wall panel 140.

[0054] The second flow is filtered when passing the filter wall 122 of the second filter panel and joins the first, now filtered, air flow in the space between the second wall panel 120 and the outlet wall panel 140. From this space the filtered air passes out through the outlet opening 145 in the outlet wall panel 140. [0055] Hence the filter unit too forms a complete filter unit which is sealed from the surrounding except at the inlet 135 and the outlet 145. By this means the outlet opening 145 of the filter unit too may be directly connected to an inlet opening in the mask (not shown) of an air purifying respirator, without the need for any additional filter housing or other sealing means.

[0056] An important advantage of the manufacturing method and the filter unit is that the construction of filter unit too is modular and may easily be adapted to different applications by selecting the number of filter panels comprised in the stack. Thereby the total area of the filtering material included in the filter unit and exposed to the unfiltered air may easily be adapted by selecting any desirable number of filter panels forming part of the stack.

[0057] The aspects of the present disclosure have mainly been described above with reference to a few embodiments and examples thereof. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.