IMPROVEMENTS RELATING TO SEALING MEMBERS

Abstract

There is provided a method of manufacturing a sealing member (42). The method comprises the steps of: (a) providing a mould having a cavity, a polymer injection port and a gas inlet port (38); (b) injecting a polymer and a blowing agent through the polymer injection port (28) into the cavity of the mould; and (c) introducing gas through the gas inlet port (38) into the cavity of the mould, to form a sealing member (42). The sealing member (42) comprises an internal chamber (44) at least partially bounded by a resiliently deformable enclosing wall formed of the polymer, the enclosing wall including an external surface, the external surface having a form that is determined by the cavity of the mould.

Claims

1. A method of manufacturing a sealing member, the method comprising the steps of: (a) providing a mould having a cavity, a polymer injection port and a gas inlet port; (b) injecting a polymer and a blowing agent through the polymer injection port into the cavity of the mould; and (c) introducing gas through the gas inlet port into the cavity of the mould, to form a sealing member, wherein the sealing member comprises an internal chamber at least partially bounded by a resiliently deformable enclosing wall formed of the polymer, the enclosing wall including an external surface, the external surface having a form that is determined by the cavity of the mould.

2. A method of manufacturing a sealing member according to claim 1, wherein the dimensions of the external surface are determined by the cavity of the mould, and/or wherein the volume of the sealing member is determined by the cavity of the mould.

3. (canceled)

4. A method of manufacturing a sealing member according to claim 1, wherein the final form of the material formed from the polymer and the blowing agent may be determined by the cavity of the mould, and/or wherein the sealing member fully sets or fully solidifies in the cavity of the mould.

5. A method of manufacturing a sealing member according to claim 1, wherein the shape and/or dimensions of the external surface matches, or corresponds to, the shape and/or dimensions of the cavity of the mould and/or wherein the volume of the sealing member matches, or corresponds to, the volume of the cavity of the mould.

6. (canceled)

7. A method of manufacturing a sealing member according to claim 1, wherein the sealing member adopts its final form in the cavity of the mould.

8. A method of manufacturing a sealing member according to claim 1, wherein the sealing member cools in the cavity of the mould to a temperature low enough for the sealing member to undergo no substantial change in inherent shape or dimensions upon removal from the cavity of the mould.

9. (canceled)

10. (canceled)

11. A method of manufacturing a sealing member according to claim 1, wherein the blowing agent is a physical blowing agent that provides gas expansion by a physical process.

12. (canceled)

13. A method of manufacturing a sealing member according to claim 11, wherein the blowing agent is caused to expand by one of, or a combination of, the application of heat and a reduction in pressure on injection of the polymer and blowing agent mix into the cavity of the mould.

14. A method of manufacturing a sealing member according to claim 1, wherein the blowing agent expands in the cavity of the mould.

15. A method of manufacturing a sealing member according to claim 1, wherein the sealing member is a sealing member for a respiratory interface device, the external surface is a patient-contacting surface, and the patient contacting-surface provides an anatomical fit with a patient.

16. A method of manufacturing a sealing member according to claim 15, wherein the patient-contacting surface has a leading portion, which is a portion that contacts a surface of the patient before any deformation of the sealing member, that is anatomically shaped at least in the direction of engagement of the sealing member with a surface of the patient, such that the position of the leading portion of the patient-contacting surface varies in this direction, at different positions along the patient-contacting surface.

17. A sealing member manufactured by the method according to claim 1.

18. A respiratory interface device comprising a sealing member manufactured by the method according to claim 1.

19. A sealing member comprising an internal chamber at least partially bounded by a resiliently deformable enclosing wall, the enclosing wall including an external surface, the enclosing wall having a plurality of gas pockets formed therein, the sealing member having the form of a loop, and the internal chamber of the sealing member being continuous and extending around at least a majority of the loop.

20. A sealing member according to claim 19, wherein the internal chamber has a central longitudinal axis that follows a curved path, and the curved path extends around at least the majority of the loop.

21. A sealing member according to claim 19, wherein the gas pockets have an appearance akin to bubbles, a cellular structure, or a matrix of holes.

22. A sealing member according to claim 19, wherein the majority of gas pockets have a diameter in the range of 50-500 μm.

23. A respiratory interface device comprising a sealing member as claimed in claim 19.

24. A respiratory interface device comprising a body portion and a sealing member, the body portion comprising a first polymer, and the sealing member comprising a second polymer, the sealing member being fixed to the body portion, wherein the sealing member comprises an internal chamber at least partially bounded by a resiliently deformable enclosing wall formed of the second polymer, the enclosing wall including a patient-contacting surface and having a plurality of gas pockets formed therein, the sealing member having the form of a loop, and the internal chamber of the sealing member being continuous and extending around at least a majority of the loop.

25. A method of manufacturing a sealing member according to claim 1, wherein the gas is first introduced through the gas inlet port into the cavity of the mould after the cavity of the mould is at least partially charged by the mixed polymer and blowing agent, and/or wherein the polymer and the blowing agent are injected through the polymer injection port into the cavity of the mould such that the cavity of the mould is only partially charged.

Description

[0162] Practicable embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0163] FIG. 1 is a rear view of a mask body formed in a first shot of a two-shot moulding method according to a first embodiment of the invention;

[0164] FIG. 2 is a schematic representation of a first stage of a second shot of the two-shot moulding method according to a first embodiment of the invention, in which a mixture of a polymer melt and a blowing agent of a second shot is being introduced;

[0165] FIG. 3 is a schematic representation of a second stage of the second shot of the two-shot moulding method according to a first embodiment of the invention, in which the mixture of the polymer melt and the blowing agent of the second shot has been fully introduced;

[0166] FIG. 4 is a schematic representation of a third stage of the second shot of the two-shot moulding method according to a first embodiment of the invention, in which a gas is partially introduced into the mixture of the polymer melt and the blowing agent of the second shot;

[0167] FIG. 5 is a schematic representation of a fourth stage of the second shot of the two-shot moulding method according to a first embodiment of the invention, in which the gas is fully introduced into the mixture of the polymer melt and the blowing agent of the second shot;

[0168] FIG. 6 is a respiratory mask formed by the two-shot moulding method according to a first embodiment of the invention, in which the polymer and gas inlets for the second shot are shown;

[0169] FIG. 7 is a first perspective view of a respiratory mask formed by two-shot moulding method according to a second embodiment of the invention; and

[0170] FIG. 8 is a second perspective view of the respiratory mask formed by the two-shot moulding method according to the second embodiment of the invention.

[0171] The method according to an embodiment of the invention illustrated in FIGS. 1-6 is a two-shot injection moulding method for manufacture of a respiratory mask.

[0172] The injection moulding process typically involves apparatus comprising injection units that each include an outlet nozzle, a tool that defines the mould, and a clamp unit. The clamp unit is arranged to move a component of the mould tool between a closed configuration, in which the polymer melt may be injected into the cavities of the mould, and an open configuration, in which the formed article may be removed from the mould tool.

[0173] The mould tool defines a mould that is provided with a first cavity and a second cavity, with the first cavity having a polymer injection port for introducing a polymer melt into that cavity and the second cavity having a polymer injection port for introducing a polymer melt and a blowing agent into that cavity, each cavity being defined by interior walls of the mould.

[0174] A first injection unit for the first shot of the two-shot injection moulding method is provided with a first polymer melt which, in this embodiment, is polypropylene (PP), a thermoplastic. The first polymer melt is heated in the injection unit until it is soft enough to flow, and the outlet nozzle of the injection unit is moved into engagement, and fluid communication, with the injection port of the first cavity of the mould.

[0175] In addition, a second injection unit for the second shot of the two-shot injection moulding method is provided with a mixture of a second polymer melt and a blowing agent. In this embodiment, the second polymer melt is a thermoplastic elastomer (TPE), and the blowing agent is a plurality of microspheres, provided in masterbatch form. The blowing agent is added to the second polymer melt using a volumetric dosing unit to ensure an even distribution throughout the second polymer melt. The second polymer melt and the blowing agent are heated in the second injection unit until soft enough to flow, and the outlet nozzle of the second injection unit is moved into engagement, and fluid communication, with the injection port of the second cavity of the mould.

[0176] In the first shot of the method according to the first embodiment of the invention, the mould is moved to its first-shot configuration. The first injection unit then applies pressure to the first polymer melt, eg using a piston and cylinder arrangement (which may also be known in the field as a screw and barrel arrangement), and injects the first polymer melt through the outlet nozzle and through the polymer injection port into the first cavity of the mould. The polymer melt within the first cavity is then allowed to commence cooling, while the pressure applied to the polymer melt is maintained, until the polymer melt is partially solidified.

[0177] The polymer melt injected into the first cavity takes the form of a mask body 10. This mask body is shown in FIG. 1, with the mould not shown for clarity.

[0178] The mask body 10 comprises a peripheral edge 16, and a tapered wall 12 that extends forwardly and inwardly from the peripheral edge 16 to a tubular connector 14. The tubular connector 14 is a conventional male or female cylindrical connector, eg 22 mm diameter, for connection to a respiratory circuit. The tapered wall 12 is generally dome-shaped, with a mouth portion having a generally annular cross-section, in a plane that corresponds to the plane of a patient's face, in use, ie the frontal plane, and a narrowed nose portion that is generally triangular in shape, with a rounded apex for engagement with the bridge of the nose of the patient. In the mask body shown in FIG. 1, the nose portion of the tapered wall 12 also includes a narrowed portion along the longitudinal axis of the mask body, extending from the tubular connector 14 towards the rounded apex of the nose portion of the tapered wall 12. This narrowed portion of the tapered wall 12 defines side surfaces that may be gripped by a user, eg in a pinching action.

[0179] Once the mask body 10 has been formed, in a solidified or partially solidified state, in the first shot of the two-shot injection moulding method, the mould is then moved into the second-shot configuration, such that the second cavity of the mould is in fluid communication with the peripheral edge 16 of the mask body 10 and a border region of the surface of the mask body 10 adjacent to the peripheral edge 16.

[0180] In a second shot of the method according to the first embodiment of the invention, whilst the mask body 10 remains in a solidified or partially solidified state, the second injection unit applies pressure to the polymer melt-blowing agent mix, eg using a piston and cylinder arrangement, and injects the second polymer melt-blowing agent mix through the outlet nozzle and through the polymer injection port into the second cavity of the mould.

[0181] FIG. 2 shows the second polymer melt-blowing agent mix 20 partially introduced into the second cavity, and FIG. 3 shows the second polymer melt-blowing agent mix 20 fully introduced into the second cavity.

[0182] The microspheres comprise a hydrocarbon core contained within a thermoplastic shell. Upon entering the second cavity, which is heated, the hydrocarbon core expands, and the thermoplastic shell gets gradually thinner, but maintains the shape of the microsphere so that the hydrocarbon is maintained therein. As the hydrocarbon core starts to expand, the volume of the second polymer melt-blowing agent mix 20 is increased, and hence, the volume of the cavity that is taken up by the second polymer melt-blowing agent mix 20 after injection into the cavity of the mould is greater than if the polymer were to be injected alone.

[0183] The second polymer melt-blowing agent mix 20 only partially charges the second cavity, as shown in FIG. 3, and hence the volume of the second polymer melt-blowing agent mix 20 is less than the volume of the second cavity. Since the polymer injection port 28 for the second cavity is disposed at the apex of the nose portion of the mask body 10 (see FIG. 6), and the second cavity extends in both directions from the polymer injection port 28 around the peripheral edge 16 of the mask body 10, the second polymer melt-blowing agent mix 20 flows along the second cavity in two branches 21, 22 from the polymer injection port 28, and extends substantially the same distance into the second cavity in each branch 21, 22.

[0184] Once the second polymer melt-blowing agent mix 20 has been fully introduced into the second cavity, and partially charged the second cavity, nitrogen gas 30 is introduced into the second polymer melt-blowing agent mix 20 in the second cavity through a gas inlet port 38 (see FIG. 6). The gas inlet port 38 is situated adjacent to, and orientated perpendicularly to, the polymer injection port 28 for the second cavity. The gas inlet port 38 extends from a wall of the second cavity into a central region of the second cavity, such that the gas forms a bubble within the second polymer melt 20 in the second cavity.

[0185] Since the gas inlet port 38 is also disposed at the apex of the nose portion of the mask body 10, and the second cavity extends in both directions from the gas inlet port 38 around the peripheral edge 16 of the mask body 10, the bubble of gas 30 flows along a central axis of the second polymer melt 20 in the second cavity in two branches 31, 32 from the gas inlet port 38.

[0186] FIG. 4 shows the gas 30 partially introduced into the second polymer melt-blowing agent mix 20 of the second cavity, and FIG. 5 shows the gas fully introduced into the second polymer melt-blowing agent mix 20 of the second cavity.

[0187] As shown in FIGS. 4 and 5, the introduction of gas 30 moves the second polymer melt-blowing agent mix 20 even further along the second cavity, towards the chin region of the mask body 10, until the two branches 21, 22 of the second polymer melt-blowing agent mix 20 meet, mix and join in the chin region of the mask body 10. In this embodiment, the gas 30 introduced into the second polymer melt-blowing agent mix 20 in the second cavity is sufficient to form a thin-walled sealing cushion 42 from the second polymer melt-blowing agent mix 20, with a gas-charged internal chamber 44. However, the gas 30 introduced into the second polymer melt-blowing agent mix 20 in the second cavity remains in two branches 31, 32, and does not meet at the chin region of the mask body 10. Instead, the two branches 31, 32 of the gas-charged internal chamber 44 each terminate with a tapered end portion, with each tapered end portion being disposed to each side of a solid portion of the second polymer melt-blowing agent mix, ie a portion of the second polymer melt-blowing agent mix that does not contain a gas-charged interior, that forms a chin region 46 of the sealing cushion 42.

[0188] Once the sealing cushion 42 of the respiratory mask has been formed, the mask body 10 and the sealing cushion 42 are allowed to cool and completely solidify, whilst the pressure applied to the polymer melt-blowing agent mix by the gas 30 is maintained. The second polymer-blowing agent mix will bond to the border region and the peripheral edge of the mask body 10, such that the mask body 10 and the sealing cushion 42 of the respiratory mask are bonded together. There is therefore no need for additional assembly steps, such as gluing, to fix the mask body 10 and the sealing cushion 42 together.

[0189] The second cavity of the mould is shaped to provide the sealing cushion 42 of the respiratory mask with an anatomical shape, which is configured to correspond to the contours of a patient's face about their nose and mouth.

[0190] The sealing cushion 42 of the respiratory mask comprises a thin enclosing wall surrounding a gas-charged internal chamber 44. Furthermore, since the gas inlet port 38 extends from a wall of the second cavity into a central region of the second cavity, the wall of the sealing cushion 42 of the respiratory mask forms around the gas inlet port 38, which provides an aperture in the wall of the sealing cushion 42 of the respiratory mask when the respiratory mask is removed from the mould. This aperture in the wall of the sealing cushion 42 of the respiratory mask provides fluid communication between the gas-charged internal chamber 44 of the sealing cushion 42 of the respiratory mask and ambient air.

[0191] FIGS. 7 and 8 show a respiratory mask 100 that has been formed by a two-shot moulding method according to a second embodiment of the invention. This respiratory mask 100 is identical to those respiratory masks formed by the first embodiment of the method according to the invention, as described above, save for the location of the aperture 138 formed by the gas inlet port 38.

[0192] In the respiratory mask 100 formed by the second embodiment of the method according to the invention, the aperture 138 formed by the gas inlet port is located in the mask body 112 and an underlying wall of the sealing cushion 142, rather than in the deformable wall of sealing cushion 142 that extends from the mask body 112. This location of the aperture 138 is achieved by providing a mould in which the gas inlet port 38 extends from a wall of the first cavity of the mould and into a central region of the second cavity, in a second-shot configuration of the mould. In this arrangement, when the first polymer is injected into the first cavity of the mould to form the mask body 112 the mask body 112 forms around the gas inlet port 38. In a second-shot configuration of the mould, the gas inlet port 38 extends through the mask body 112 in the first cavity and projects into the second cavity. In this arrangement, when the second polymer-blowing agent mix is injected into the second cavity of the mould to form the sealing cushion 142, a wall of the sealing cushion 142 that underlies an adjacent wall of the mask body 112 forms around the gas inlet port 38. An aperture 138 is therefore formed in the mask body 112, and the underlying wall of the sealing cushion 142, of the respiratory mask 100 when the respiratory mask 100 is removed from the mould. This aperture 138 provides fluid communication between the gas-charged internal chamber of the sealing cushion 42 of the respiratory mask 100 and ambient air.

[0193] In a third embodiment of a method according to the invention, an overmoulding process is used. This differs from the first and second embodiments, which are two-shot moulding processes, in that the mask body formed of the first polymer (the substrate) is transferred to a second cavity in a second mould, typically once substantially or completely solidified, before the second polymer-blowing agent mix is injection moulded into the second cavity, and hence “overmoulds” the mask body. In this embodiment, the sealing member formed by the second polymer-blowing agent mix is fixed to the mask body formed by the first polymer by one or more of a chemical bond and a mechanical bond.

[0194] Furthermore, any of the first, second and third embodiments may also be used with a thermosetting polymer, eg for the sealing member. For example, liquid silicone rubber (LSR) may be the second polymer for forming the sealing member. However, where a thermosetting polymer is used, the injection moulding step and the associated apparatus will differ to these described above, as thermosetting polymers typically require heat to initiate curing in order to harden. For liquid silicone rubber, a liquid injection moulding (LIM) process is typically used.

[0195] The materials commonly used in the LIM process are silicones and acrylics. Utilising a pump, the LIM process brings together a base-forming plastic, which can be strengthened with additives and fibres, and a catalyst. Each will be pumped in a 1:1 ratio into a static mixer, which triggers the mixing reaction, to form liquid silicone rubber (LSR), for example. The outlet nozzle of the injection unit is moved into engagement, and fluid communication, with the injection port of the cavity of the mould. The liquid mixture is then injected into the cavity of the mould along with a blowing agent.

[0196] Described below are examples of respiratory masks formed by the applicant during testing, using the above-described methods.

EXAMPLE 1

[0197] In a first example, a polymer-blowing agent mix consisting of 95% thermoplastic elastomer and 5% blowing agent in the form of microsphere masterbatches produced by KCD GmbH (Otto-Schott-Strafle 5, 99427 Weimar, Deutschland) produced a sealing member having a substantially uniform enclosing wall and internal chamber, with the enclosing wall having a wall thickness that varied between 2 mm and 3 mm.

EXAMPLE 2

[0198] In a second example, a polymer-blowing agent mix consisting of 90% thermoplastic elastomer and 10% blowing agent in the form of microsphere masterbatches produced by Expancel (Nouryon, Pulp and Performance Chemicals AB, Box 13000, SE-850 13 Sundsvall, Sweden) produced a sealing member having a substantially uniform enclosing wall and internal chamber, with the enclosing wall having a wall thickness that varied between 1.5 mm and 2 mm.