TWI854020B - Heating chamber for an aerosol generating device and method of manufacturing the same - Google Patents

Abstract

A method of manufacturing a heating chamber for an aerosol generating device includes the steps: providing a metal tubular member comprising a tubular side wall with an open end; the tubular side wall having a thickness of no more than 0.15 mm; inserting the tubular member into a tubular mould, the inner surface of the tubular mould having a shaping profile with at least one protrusion or recess; sealing the open end of the tubular member; and injecting a fluid under pressure into the tubular member to outwardly deform the tubular member such that it conforms to the shaping profile of the surrounding tubular mould. By using a fluid pressure to shape the tubular member, a required profile shape can be transferred to the tubular member with high precision, while maintaining the thickness of the chamber walls below 0.15 mm to provide efficient heat transfer to a consumable during use.

Description

Heating chamber for aerosol generating device and method for manufacturing the same

The present invention relates to a method for manufacturing a heating chamber, in particular a method for manufacturing a heating chamber for an aerosol generating device.

Heating chambers are used in a wide range of applications that generally require a device to contain and transfer heat to a substance to be heated. One such application is in the field of aerosol generating devices, such as reduced risk nicotine delivery products, including e-cigarettes and tobacco vapor products. Such devices heat aerosol generating material in the form of a consumable within a heating chamber to produce a vapor for inhalation by the user.

The heating chamber typically includes a thermally conductive shell or housing that defines an internal volume that holds the consumables and an opening that can receive the consumables. Heaters can be used internally or externally to provide increased temperature to the heating chamber. Most commonly, such heating chambers are heated from the outside while the thermally conductive housing transfers heat to the internal volume. One means of heating such heating chambers is to use a thin film heater that conforms to the surface of the heating chamber to ensure effective heating of the consumables received in the chamber.

Typically, the heating chamber needs to be formed with a specific shape to accept a specific type of consumable. The interior surface of the heating chamber may also need to adopt a specific surface profile shape to retain the consumable and effectively transfer heat to the consumable. One problem with known methods for making such heating chambers is that it is difficult to accurately control the specific shape of the heating chamber while controlling the thickness of the heating chamber wall to ensure optimal heat transfer. In particular, the known methods of making heating chambers are unable to provide thin chamber walls to obtain good heat transfer through the heating chamber while controlling the shape of the heating chamber with high precision. In particular, it is difficult to form thin metal sheets as required without damaging the formed chamber or creating weaknesses. Known methods are also limited by the complexity of the shapes that can be provided to the heating chamber contour, which limits the extent to which such methods can be optimized for a particular application.

The object of the present invention is to make progress in solving these problems, to provide a method of manufacturing a heating chamber which can provide a heating chamber with the required thickness to optimize heat conduction to the consumables, while allowing the heating chamber to be precisely shaped so that the heating chamber can be optimized for a specific application.

According to a first aspect of the present invention, a method for manufacturing a heating chamber for an aerosol generating device is provided, the method comprising: providing a metal tubular member, the metal tubular member comprising a tubular side wall having an open end and a closed end; the tubular side wall having a thickness of no more than 0.15 mm; inserting the tubular member into a tubular mold, the inner surface of the tubular mold having a forming profile with at least one protrusion or recess; sealing the open end of the tubular member; injecting a fluid into the tubular member under pressure to deform the tubular member outwardly, thereby making the tubular member conform to the forming profile of the surrounding tubular mold. By using fluid pressure to form the tubular member, the desired contour shape can be transferred to the tubular member with high precision, while keeping the thickness of the chamber wall below 0.15 mm to provide effective heat transfer to the consumable during use. In addition, the method of the present invention allows more complex surface contour shapes to be transferred to the heating element, which is difficult to achieve using known methods. Using fluid pressure and a tubular mold, a wider range of surface shapes can be transferred to the tubular member.

The steps of inserting the tubular member into a tubular mold and injecting a fluid into the tubular member under pressure to deform the tubular member outward may be collectively referred to as a hydraulic forming step in the following disclosure.

The metal tubular member preferably comprises stainless steel. The thickness of the tubular sidewall is preferably 0.1 mm or less, or more preferably between 0.07 mm and 0.09 mm. This allows for effective heat transfer to the consumables through the sidewall of the heating chamber while maintaining sufficient structural stability. The tubular member has a closed end opposite the open end, wherein preferably the closed end has a thickness of 0.2 mm to 0.6 mm, which further increases the structural rigidity of the heating chamber. In a possible embodiment, the tubular member is cut along its length after the fluid injection step to provide a tubular member with two open ends for use in applications requiring a heating chamber with openings at both ends.

The fluid pressure is preferably provided by injected water at a pressure of up to 250 bar. The specific pressure used depends on the specific material, thickness and surface profile to be delivered. The pressure applied can be varied during the hydroforming process. The required pressure can be determined by conventional experiments with new materials or by simulation.

The tubular mold is preferably configured in two or more parts which are fixed together during fluid injection and can be moved apart to release the formed tubular component.

Preferably, the forming profile of the tubular mold comprises an annular groove in the inner surface of the mold, the annular groove extending around the circumference of the tubular mold, so that after the injection of the fluid, the tubular component comprises an annular flange. In this way, the annular flange can be provided with precisely controlled dimensions. The annular flange can be used to mount the heating chamber in the device in a precise and reliable manner.

The annular groove preferably extends along the length of the tubular mold to provide a circumferential channel around the inner surface of the tubular mold. In other words, the groove can have a relatively large width in the direction corresponding to the long axis of the tubular member, for example, a width greater than 1 mm, preferably greater than 3 mm. The cross-sectional profile of the groove can be substantially rectangular, square or trapezoidal.

Preferably, the tubular mold comprises a tubular body, preferably a cylindrical body. In a particularly preferred example, the annular groove is formed by a length segment of the tubular body having an inner diameter greater than the rest of the tubular body; so that the annular flange comprises a corresponding length segment of the tubular member having a diameter greater than the rest of the length of the tubular member. In other words, the groove in the inner surface of the tubular mold has a depth defined by the length of the side walls of the groove, which are appropriately perpendicular to the inner surface of the tubular body. Preferably, the side walls of the annular groove are connected by a base surface that is substantially perpendicular to the inner surface of the tubular body. In this way, both the annular groove of the tubular mold and the annular flange of the tubular component have a substantially rectangular cross-sectional profile. This shape is particularly advantageous for the further processing of the tubular component and for its installation in the device. For example, this allows a cylindrical lip to be formed in a simple manner by subsequent cutting of the annular flange.

The method may further comprise the step of cutting the tubular member through the annular flange to provide a tubular member of reduced length having an annular collar at the open end. In particular, the tubular member may be truncated by cutting the tubular member through the annular flange in a cross section of the annular flange (i.e., substantially normal to its major axis). The annular collar around the open end is particularly useful for mounting a heating chamber in an apparatus. The annular collar may be cut again to provide a circumferential planar lip around the open end. In particular, by cutting the annular collar in a direction generally parallel to the long axis, the radial extension of the annular collar can be reduced so that the remaining lip is substantially planar and does not extend significantly along the length of the tube. In other words, the annular collar can be adjusted to provide a circumferential planar lip. In an alternative method, the annular flange can be cut in a single step to form the circumferential lip. The circumferential planar lip is particularly conducive to accurately and safely installing the heating chamber in the device. The term "lip" is used to refer to an annular extension that is substantially planar (i.e., has a depth corresponding to the thickness of the tubular component in the direction of the tubular axis). The term "collar" is used to refer to an annular extension around the opening that has a greater depth in the direction of the tubular axis.

The method preferably further comprises applying an inward pressure on the outer surface of the tubular member to provide one or more inwardly extending projections on the inner surface of the tubular member. This can be implemented using a press member to apply pressure on the outer surface, and the inward pressure can be applied during fluid injection or in a separate process before or after molding with fluid pressure. For example, the formed tubular member formed during the fluid injection step can be supported from the inside, such as using a former and pressure applied from the outside, to produce one or more inwardly extending projections on the inner surface of the tubular member.

Preferably, the method comprises applying an inward pressure on the outer surface of the tubular member to provide one or more inwardly extending projections on the inner surface of the tubular member as the fluid is injected under pressure into the tubular member. In this way, both positive and negative surface features may be provided on the surface of the tubular member in the same processing step, i.e. both projections and recesses may be on the outer surface of the tubular member (causing corresponding features on the inner surface of the tubular member). By injecting the fluid while providing the inward pressure, surface features may be provided on the tubular member with increased precision. In particular, when the pressing member is pressed on the outer surface of the region of the inner surface of the tubular member, the fluid pressure can be applied as pressure to the region so that under the application of the fluid pressure, the wall of the tubular member more closely conforms to the shape of the pressing member. This allows surface features to be provided with high geometric accuracy, for example with a radius of 0.1 mm to 0.2 mm.

Where inward pressure is applied to provide one or more inwardly extending projections, this may be achieved by pressing a plurality of elongated ridges into the outer surface of the tubular member to provide a plurality of corresponding elongated projections running lengthwise on the inner surface of the tubular member, the projections being positioned around the circumference of the tubular member. As fluid is injected under pressure into the tubular member, the elongated ridges may be pressed into the outer surface so that the sidewalls of the tubular member more closely conform to the shape of the elongated ridges. The elongated ridges are preferably aligned with the long axis of the tubular member and may be positioned to provide elongated projections running along a central portion of the length of the tubular member on the inner surface. The elongated protrusions may be spaced apart from the base of the tubular member and spaced apart from the open end of the tubular member. The elongated ridges may run along approximately one third of the length of the tubular member. The plurality of elongated ridges may be disposed on an inner surface of the tubular mold.

The step of applying inward pressure on the outer surface of the tubular member may additionally or alternatively include applying pressure at one or more contact points to provide one or more point-shaped protrusions on the inner surface of the tubular member. The point-shaped protrusions may include a plurality of protrusions periodically positioned around the circumference of the inner surface of the tubular member. The point-shaped protrusions may be configured to improve the grip of the substrate carrier in the heating chamber while limiting heat transfer in this area. Each point-shaped protrusion may include a rounded protrusion, such as a partially spherical protrusion. The point-shaped protrusion may have a radius between 0.05 mm and 0.25 mm, preferably 0.1 mm to 0.2 mm. Other shapes of protrusions may be formed using this method, such as truncated pyramidal protrusions, etc.

Preferably, the inwardly applied pressure is provided by one or more movable parts of the tubular die; and when the tubular member is inserted into the tubular die and fluid is injected under pressure, one or more inwardly extending projections are provided by applying inward pressure to one or more movable parts of the tubular die. Preferably, the movable part of the tubular die initially contacts the outer surface of the tubular member and moves radially inward against the outer surface to apply pressure when the fluid is injected under pressure.

The tubular mold may include a plurality of movable portions. One or more of the movable portions may be configured to provide different forms of inwardly extending projections. The movable portions may be movable together and/or independently to provide different forms of inwardly extending projections simultaneously or sequentially.

In one example of the present invention, the tubular mold includes a first movable part and a second movable part, the first movable part is arranged to provide a plurality of elongated protrusions running along the length direction on the inner surface of the tubular member, and the second movable part is arranged to provide a plurality of point-shaped protrusions arranged around the circumference of the inner surface of the tubular member; wherein the first movable part and the second movable part are positioned at different positions along the length of the tubular mold. The first movable part and the second movable part can be arranged to apply pressure simultaneously and/or sequentially.

The tubular mould may be arranged to provide different penetration depths of the inwardly extending protrusions in the heating cavity. In particular, the movable parts may be sized so that the penetration depth of the formed point-shaped protrusions may be relatively small compared to the penetration depth of the formed elongated protrusions. This has the advantage of providing an effective grip without excessive restraint in the rigid area of the consumable where clamping is desired.

Preferably, when the tubular member is inserted into the tubular mold and fluid is injected under pressure, an inwardly applied pressure is provided so that one or more inward projections and the annular flange are formed simultaneously, thereby providing an efficient method in which the final shape of the heating chamber is formed in one step.

The tubular member may be provided by: stamping a metal sheet to provide a metal disc blank; and deep drawing the metal disc blank to form a tubular cup having an open end and a closed end. Deep drawing may involve using a multi-stage deep drawing process in which the metal disc blank is progressively stretched to increase the length of the tubular cup and reduce the thickness of the side wall. Oil or soap may be used as a lubricant. The method may further include the step of annealing the tubular member one or more times during and/or after deep drawing.

Preferably, the method includes forming the metal disc blank into an initial cup shape; annealing under vacuum or inert gas; and deep drawing the initial cup shape into an elongated tubular cup having a reduced tubular wall thickness. The deep drawing process may include ironing the tubular cup to reduce the wall thickness. Since plastic deformation of the metal during the initial deep drawing may cause the metal to become hard, making further processing of the metal more difficult, the intermediate annealing step allows the initial cup-shaped member to be deep drawn to an increased length with a reduced tubular wall thickness. A further annealing step may be performed prior to the hydroforming step (injecting a fluid under pressure) so that the tubular member becomes softer and therefore easier to mold during hydroforming.

The initial forming of the initial metal cup can be carried out by cutting round plates from the metal strip using a multi-stage punch press and forming them into smaller cups. The initial smaller cups are shallow and are then deep drawn to the required length in several steps (preferably after an intermediate annealing step), using ironing to reduce the wall thickness to within the required range.

Annealing can be carried out in a low pressure vacuum furnace (e.g. at a pressure of 10 ^-2 to 10 ^-4 mbar) or in an inert gas furnace. The reduced pressure or inert gas protects the surface of the tubular cup from oxidation.

Preferably, the deep drawing process is performed to provide a tubular cup having an inner diameter of less than 10 mm, preferably less than 8 mm, and a length of greater than 30 mm. Deep drawing can provide tubular components with a length of greater than 50 mm, for example up to 65 mm. After the hydraulic forming step, the tube can be shortened to provide a formed tubular component with a length of between 20 mm and 40 mm, preferably 25 mm to 35 mm.

Preferably, deep drawing is performed from a metal disc blank to provide a tubular cup having a tubular wall with a side thickness of 0.05mm to 0.1mm, more preferably 0.07mm to 0.09mm. Side wall thicknesses in these ranges provide for efficient heat transfer through the chamber to the consumable during use, and also enable subsequent hydraulic forming with precise inwardly extending projections.

Deep drawing may be performed to provide a tubular cup with a bottom wall having a thickness of 0.2 mm to 0.6 mm, preferably 0.4 mm. In particular, the metal sheet preferably has a thickness of 0.2 mm to 0.6 mm, preferably 0.4 mm, and the deep drawing process maintains this thickness as the base of the tubular member. By providing the closed end with an increased thickness relative to the side walls, the heating chamber has increased mechanical strength while maintaining the optimal heat transfer properties provided by the reduced thickness of the side walls.

Preferably, the deep drawing process provides a tubular member including a central recess in the outer surface of the closed end. In particular, the recess may be produced during the initial stamping of the metal disc blank. The central recess in the closed end preferably provides a corresponding protrusion on the inner base surface of the tubular member. The central recess of the closed end may assist in mounting the heating chamber within the device. The central recess may further assist in controlling the insertion depth of the consumable within the device. For example, when used in an aerosol generating device, when the consumable is inserted, the central recess will encounter the protrusion on the inner base surface, which limits further insertion. In this configuration, air in the chamber may flow into the end of the consumable in the space around the central protrusion. In use, the central protrusion may further assist in providing heat transfer to the end of the consumable in contact with the protrusion.

The method may further include wrapping a thin film heater around an outer surface of the tubular member. The method may further include positioning a temperature sensor at least partially within a recess on an outer surface of the heating chamber.

In another aspect of the invention, there is provided a heating chamber for an aerosol generating device, manufactured by the method of any of the preceding claims. In particular, the aerosol generating device may include a heating chamber, a thin film heater wrapped around the heating chamber; a power supply and a control circuit, the power supply and the control circuit being configured to controllably supply power to the thin film heater to heat the heating chamber. The heating chamber may be mounted in the device by a circumferential lip of the heating chamber, the lip being received in a corresponding recess in the aerosol generating device.

10: Tubular components

11: Side wall

11t: Side wall thickness

12: Open end

12t: Low thickness

13: Closed end

13t: base thickness

14: Annular flange

14a: Side wall

14L: Length

15: Lip rim

17: Protrusion

17L: Length

18: Dent

19: Protrusion

20: Tubular mold

21: Inner surface

22: Groove (annular groove)

22a: Circumferential side wall

22L: Section

23a: First movable mold part

23b: Second movable mold part

24: Open end

25: Closed end

31: Seals

32: Spray nozzle

33: External clamping element

34: Connection point

40:Metal sheet

41:Metal plate blank

41t: Initial thickness of metal plate blank

42: Volume

43: Cup pieces

100: Heating chamber

200:Aerosol generating device

201:PCB

210: Consumables

220: Thin film heater

The embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: [FIG. 1A to FIG. 1D] schematically show a method for manufacturing a heating chamber for an aerosol generating device according to the present invention; [FIG. 2A to FIG. 2C] schematically show a heating chamber manufactured according to the present invention; [FIG. 3A and FIG. 3B] schematically show a method for forming a metal disc blank for deep drawing; [FIG. 4A to FIG. 4D] schematically show a method for forming a metal tubular member according to the present invention; [FIG. 5] schematically shows an aerosol generating device including a heating chamber manufactured using the method according to the present invention.

FIG1 schematically illustrates a method for manufacturing a heated chamber 100 for an aerosol generating device. The method comprises providing a metal tubular member 10, as shown in FIG1A , having a tubular sidewall 11 with an open end 12 and an opposite closed end 13. The tubular sidewall 11 of the tubular member 10 has a sidewall thickness 11t less than or equal to 0.15 mm. The tubular member 10 is inserted into a tubular mold 20, which includes an inner surface 21 that provides a forming profile having at least one protrusion or recess or groove 22. The open end 12 of the tubular mold is then sealed, and a fluid F is injected under pressure (as shown in FIG1B ) to deform the tubular member 10 outwardly to conform to the forming profile 21 of the surrounding tubular mold 20. The method according to the invention allows the heating chamber 100 to be formed with a precisely controlled forming profile while maintaining a reduced sidewall thickness 11t. By controlling the shape and sidewall thickness 11t of the heating chamber 100 with high precision, the heat transfer through the heating chamber 100 is optimized, which ensures improved heating of consumables received in the heating chamber 100 when used in an aerosol generating device. In addition, the precise control of the shape of the sidewall 11t of the heating chamber 100 allows the heating chamber 100 to be accurately and reliably installed in the aerosol generating device.

In the example of FIG. 1 , the metal tubular member 10 is in the form of a tubular cup having an open end 12 and a closed end 13. The tubular member 10 comprises a substantially cylindrical body having a closed end 25 and an open end 24 and a side wall thickness 11t of about 0.1 mm. As shown in FIGS. 1A and 1B , the tubular member 10 is inserted into a tubular die 20, wherein the closed end 13 of the tubular member 10 abuts against the closed end 25 of the tubular die 20. The tubular die 20 has an inner surface 21 that provides a forming profile to be transferred to the outer surface of the tubular member 10. In the example of FIG. 1 , the forming profile comprises an annular groove 22 that runs around the circumference of the inner surface 21 of the tubular die 20.

As shown in Figures 1A and 1B, a fluid injection nozzle 32 is inserted into the open end 12 of the tubular member 10, the open end 24 around the tubular nozzle 32 is sealed with a seal 31, and the fluid F is injected under pressure, as shown in Figure 1B. The seal 31 is preferably positioned within the open end 12 of the tubular member and clamped in place, such as by pressing the tubular member tightly against the seal 31 by an external clamping element 33, as shown in Figures 1A and 1B. This fluid injection process can be implemented by injecting water into the tubular member 10 to apply pressure to the inner surface of the tubular member 10, thereby deforming it outwardly into the formed contour on the inner surface 21 of the tubular mold 20. The applied pressure can be up to 250 bar, and the specific applied pressure is selected according to the specific requirements of the process (e.g., the material and thickness of the tubular member 10 and the shape to be applied to the tubular member 10).

As described above, the tubular die 20 comprises a substantially cylindrical body provided with an annular groove 22 around the circumference of the inner surface 21 of the die. In this way, the tubular member 10 is deformed outwardly into the annular groove 22 under the applied fluid pressure F to provide the annular flange 14 around the circumference of the tubular member 10. In this example, the tubular die 20 has the annular groove 22 formed by a length section 22L of the cylindrical body having an inner diameter _D2 greater than the diameter _D1 of the rest of the cylindrical body. In this way, the annular flange 14 comprises a corresponding length section of the tubular member 10 having a diameter greater than the rest of the length of the tubular member 10. The annular groove 22 has a substantially rectangular profile formed by two circumferential side walls 22a which extend away from the tubular body of the mold in a direction substantially perpendicular to the long axis of the mold 20 and are connected by a surface substantially parallel to the long axis of the mold 20.

After the high-pressure fluid F is injected into the tubular member 10, the tubular member is formed to provide a corresponding annular flange 14 whose size corresponds to the inner surface of the annular groove 22 of the mold 20, as shown in FIG. 1C. In particular, the tubular member 10 has an annular protrusion having a square profile formed by a portion of the tubular member 10 having a length 14L greater than the diameter of the rest of the cylindrical body.

The method includes a further step for providing additional surface features 17, 19 in the side wall 11 of the tubular member 10 to form the formed heating chamber 100 shown in FIG. 1D. In particular, an inward pressure P can be applied to the outer surface of the tubular member 10 when the fluid is injected into the tubular member 10 so as to provide one or more inwardly extending protrusions 17, 19 on the inner surface of the tubular member 10. By applying pressure P during or after the injection of the fluid F with the nozzle 32, the protrusions 17, 19 can be provided in a variety of different ways. FIG. 1 shows a particularly preferred means of providing the inner protrusions 17, 19 using the movable parts 23a, 23b of the tubular mold 20.

As schematically shown in Figures 1A and 1B, the tubular mold 20 includes a first movable portion 23a and a second movable portion 23b, each of which is configured to apply a pressure _P1 , _P2 to the outer surface of the tubular member 10 in a radially inward direction during hydraulic forming to provide surface features 17, 19 on the surface of the tubular member 10. The movable portions 23a and 23b are positioned against the outer surface of the tubular member and move inwardly during the fluid injection step to impart the surface features 17, 19 on the tubular member 10. Applying the pressure _P1 , _P2 during the injection of the fluid into the tubular member allows the protrusions 17, 19 to be formed with high precision around the formed inner surfaces of the movable parts 23a, 23b to which the pressure P is applied. In some examples, the fluid F can be directed with the nozzle 32, particularly around the area where the pressure is applied, so as to cause the outer surface of the tubular member 10 to closely conform to the shape of the punch 23 to precisely form the protrusions 17, 19. In some examples, the pressure can be varied, for example by selecting a nozzle having a specific diameter. Controlling the parameters of the fluid injection process allows for providing rounded surface features with very small radii and protrusions with short widths. Thus, the hydraulic forming technique shown in FIG. 1 allows the protrusions 17, 19 to be formed with high geometric accuracy to have a reduced side wall thickness 11t to provide enhanced heat transfer through the heated chamber 100 when used in an aerosol generating device.

In the example of FIG. 1 , the first movable mold portion 23a (which may include a plurality of component movable portions) includes inner surface features in the form of a plurality of elongated ridges positioned periodically around the inner circumference of the inner surface of the movable mold portion 23a, the ridges being aligned with the long axis of the tubular member 10. The first movable mold portion 23a is movable to apply a pressure _P1 during the fluid injection step, as shown in FIG. 1B . After the fluid injection step, the first movable mold portion 23a thus provides corresponding elongated protrusions 17 running along the inner surface of the tubular member 10 in the lengthwise direction, as shown in FIG. 1C . A plurality of such protrusions 17 are arranged around the circumference of the inner surface of the tubular member 10. When the formed heating chamber 100 is used in an aerosol generating device, the elongated protrusions 17 provide a number of functions, including limiting the insertion depth of the consumable into the chamber, providing airflow between the protrusions, and enhancing heat transfer to the consumable, as will be described in more detail below.

The tubular mold 20 of Fig. 1 further comprises a second movable mold part 23b, which is separated from the first movable mold part 23a along the tubular axis of the mold and is positioned near the annular groove 22. The second movable mold part 23b has an inner pressing surface, which is shaped to provide a plurality of rounded point-shaped protrusions 19 arranged around the circumference of the inner surface of the tubular member. In particular, the second movable mold part 23b (which may include a plurality of movable parts, for example, each movable part is configured to provide a single protrusion) has a pressing surface including a plurality of rounded protrusions, which are periodically arranged around the circumference of the mold part 23b. The second movable mould part 23b is configured to provide a pressure _P2 against the outer surface of the tubular member 10 during fluid injection to provide the projection 19 shown in Figure 1C. The projection 19 adjacent the annular flange 14 provides additional gripping and positioning of the consumable received within the heating chamber 100.

The movable portions of the molds 23a, 23b may be used to apply corresponding pressures _P1 , _P2 during fluid injection so that the inward projections 17, 19 are formed simultaneously with the annular flange 14. Alternatively, the pressure P may be applied after initial formation of the annular flange 14, wherein the pressures _P1 and _P2 are applied to the outer surface of the tubular member 10 using the movable portions in a separate molding step while the fluid is directed specifically at portions of the inner surface of the tubular member 10 opposite the point on the outer surface where the pressure P is applied. For example, a specific fluid pressure may be selected that is optimized for each stage of the molding process, e.g., different fluid pressures may be directed to form the projections 17, 19 rather than to form the annular flange. The movable mould parts 23a, 23b may be used simultaneously or sequentially to apply the pressures _P1 , _P2 and form the corresponding protrusions 17, 19.

After the hydraulic forming step shown in FIGS. 1A and 1B , the formed tubular component 10 is removed from the tubular mold 20 as shown in FIG. 1C . In particular, the tubular mold 20 is provided in multiple parts that are fixed together during the fluid injection step. For example, the tubular mold 20 can be longitudinally divided into two parts that are connected at a connection point 34 along an interface running along the length of the mold as shown in FIGS. 1A and 1B . The multiple parts of the tubular mold 20 are then opened to release the formed tubular component 10 as shown in FIG. 1C .

Further processing steps are performed on the formed tubular member 10 shown in FIG. 1C to prepare it for use as a heating chamber 100. In particular, the tubular member 10 can then be cut through the annular flange 14 to provide a circumferential flat lip 15 around the open end 12 of the tubular member 10, as shown in FIG. 1D. This can be achieved by first cutting the annular flange 14 in a radial direction along a cutting line _C1 to reduce the length of the tubular member 10, as shown in FIG. 1C. The tubular member 10 is then cut again through the side wall 14a of the annular flange 14 in a direction parallel to the tubular axis along a cutting line _C2 . By adjusting the annular flange 14 in this manner, a planar circumferential lip 15 is provided around the circumference of the open end 12 of the tubular member 10, as shown in FIG. 1D. The circumferential lip 15 is particularly useful for mounting the tubular member 10 when used as a heating chamber 100 in an aerosol generating device. The hydraulic forming method shown in FIGS. 1A to 1D allows the circumferential lip 15 to be provided with a precise low side wall thickness 11t, which allows the heating chamber 100 to be accurately mounted in the aerosol generating device.

FIG2 illustrates a particularly preferred formed heating chamber 100 formed using the process shown in FIG1 . FIG2A schematically illustrates a side view of the formed heating chamber 100, with FIG2B and FIG2C illustrating cross-sectional views as shown by lines A-A and B-B in FIG2A . As described above, the tubular member 10 has been formed by the method of FIG1 to provide a number of features. First, a series of elongated protruding ridges 17 are provided on the inner surface of the heating chamber 100, extending over a length 17L along a central portion of the length of the heating chamber 100. In this example, the heating chamber is cut to a length of approximately 31 mm, with the elongated protrusions having a length 17L of approximately 12 mm and spaced apart from the ends 12 , 13 of the heating chamber 100. A plurality of such protrusions 17 are periodically provided around the circumference of the heating chamber 100 (as shown in the cross section of FIG. 2C ), and the protrusions have a tightly curved rounded cross section with a radius of about 0.15 mm. In particular, four protrusions 17 may be provided to be spaced 90° apart around the circumference.

The projections 17 are arranged to press into the consumables received in the heating chamber 100 to improve heat transfer from the heating chamber 100 to the received consumables. The projections also ensure that sufficient gaps are maintained between the projections for air to flow from the open side to the closed side. The projections also help to limit the distance that the consumables can be inserted into the chamber, for example by abutting against a raised and non-deformable portion of the consumables, thereby preventing the consumables from being inserted further into the chamber 100. This can ensure that the consumables are positioned at the correct insertion depth in the chamber 100 by limiting further insertion after the rigid portion of the consumables encounters the front end of the projection.

Additional dot-shaped projections 19 or "gripping projections" 19 are also provided around the circumference of the heating chamber 100, as shown in Figure 2B. The gripping projections 19 may be provided together with the second movable mold part 23b, as described above. Again, in this case, four gripping projections are provided with angular spacings of 90° between the projections. During use, the gripping projections 19 may assist in gripping and positioning the consumables within the heating chamber. As described above, the second movable mold part 23b is positioned at a defined distance from the annular groove 22 in the mold, so that when the formed tubular member 10 is cut to size, the gripping projections 19 are provided at a defined distance from the open end 12 of the heating chamber 100. In a possible mode, the dot-shaped projections 19 are omitted and only the elongated projections 17 are formed.

FIG2A also shows a circumferential planar lip 15 disposed around the open end 12 of the chamber, which is formed by cutting the annular flange 14. As clearly shown in FIG2A, the circumferential lip 15 has a low thickness 12t of about 0.07 mm to 0.09 mm, corresponding to the sidewall thickness 11t of the remaining sidewall 11 of the heating chamber 100, which is advantageous when used to install the heating chamber 100 in an aerosol generating device. The base of the heating chamber 100 has a larger base thickness 13t of about 0.4 mm, which may help provide structural stability to the heating chamber 100. The sidewall thickness 11t and base thickness 13t may be configured during the initial formation of the tubular member 10, prior to the hydraulic forming step, as will now be described with reference to FIGS. 3A to 3C .

FIG3 illustrates an additional initial step in the method of making the heating chamber 100 for providing an initial tubular member 10 for hydraulic forming. The process involves cutting a metal disc blank 41 from a metal sheet 40 (as shown in FIGS. 3A and 3B ) and then deep drawing the disc 41 into a tubular member 10 (as shown in FIG4 ) ready for hydraulic forming.

In particular, a multi-stage punch press can be used to cut circular plates 41 from a metal sheet 40 and form the circular plates into smaller cups 43, as shown in FIG. 4A. This can be part of an automated process, in which a coil 42 of metal sheet is punched to provide an initial metal disc blank 41 as shown in FIG. 3B and is pressed into an initial short cup 43 shown in FIG. 4A. The metal disc blanks can be cleaned and reduced, for example using wax and then vacuum annealed. Thereafter, the cup 43 can be deep drawn into a thin-walled tube in several steps to form the tubular component 10 used in the method according to the invention. The intermediate annealing step softens the metal and thereby increases the ease with which the metal cup can be deep drawn to the desired length.

As shown in FIG4 , during the deep drawing process, the base thickness 13t remains substantially constant, while the side wall thickness 11t gradually decreases as the initial cup 43 is stretched into the final tubular member 10 by progressive deep drawing. The initial thickness 41t of the metal disc blank is about 0.4 mm before being progressively stretched (as shown in FIG3C ) to reduce the wall thickness to less than 0.1 mm, leaving a residual thickness of 0.4 mm in the base. Ironing can be used to further reduce the side wall thickness, as schematically shown in FIGS. 4B to 4D . This deep drawing process can provide a tubular cup having a tubular wall with a side thickness between 0.07 mm and 0.09 mm. This thickness range provides enhanced heat transfer through the heating chamber to the heating consumable in use while maintaining a sufficiently mechanically stable structure.

The deep drawing process also provides an indentation 18 in the base 13 of the tubular member 10. This can be advantageous in retaining the consumable in the base while leaving a gap for the aspirated air to flow through the end of the consumable. This can also be advantageous in mounting the heating chamber 100 in an aerosol generating device. After the multi-stage deep drawing process, the tubular member can be annealed again using a vacuum or an inert gas. For example, the tubular cup formed by the initial deep drawing can be annealed in a low pressure vacuum furnace (e.g., at a pressure between 10-2 mbar and 10-4 mbar), or in an inert gas furnace. The reduced pressure or inert gas protects the surface of the tubular cup from oxidation. Due to the plastic deformation of the metal during deep drawing, the metal becomes very hard, so the annealing step solves this problem, making the tubular member easier to mold during the hydroforming process. The resulting tubular member 10 can then be used in the hydroforming process shown in Figures 1A to 1D to form the formed heating chamber 100.

FIG5 shows a heating chamber 100 for an aerosol generating device 200 manufactured by the method of the present invention. In particular, the heating chamber 100 is installed in the aerosol generating device, wherein the open end 12 is provided at one end of the device to receive a consumable 210 to be heated for generating an aerosol for inhalation by a user. The heating chamber 100 is preferably wrapped with a thin film heater 220 around the outer surface to heat the side walls and the internal volume of the chamber. The thin film heater 220 is connected to the PCB 201 and the battery 202 to selectively supply power to the thin film heater, thereby heating the heating chamber 100 to a controlled temperature. Since the side wall thickness 11t of the tubular side wall 11 of the heating chamber 100 can be precisely controlled and maintained at a low thickness of no more than 0.15 mm, heat transfer from the thin film heater 220 to the inner volume of the chamber is enhanced. In addition, since the protrusions 17, 19 can be formed on the inner surface of the heating chamber 100 with high precision, the thickness and extension distance of the protrusions can be carefully controlled to provide the required grip and increased heat transfer to the consumable 210, while not extending to a degree sufficient to prevent the consumable 210 from being inserted into the heating chamber 100.

The elongated protrusion 17 can be positioned with high precision so as to engage the aerosol generating portion 212 of the consumable 210 and contact the rigid portion 211 of the consumable 210 when the consumable is inserted into the chamber 100 to prevent the consumable 210 from being further inserted, thereby holding the consumable 210 in the correct position so that the aerosol generating portion 212 is effectively heated by the film heater 220. When used in the device, the increased base thickness 13t of the base portion 13 of the heating chamber 100 provides structural rigidity to the heating chamber 100. The indentation 18 (i.e., the central protrusion) provided on the base 13 of the heating chamber 100 can contact the surface of the consumable 210 to prevent further insertion and allow an air flow path around the exposed outer circumferential portion of the consumable when the consumable 210 is received in the chamber 100.

The method of the present invention solves the important problem of ensuring that the thickness of the heating chamber side wall is accurately controlled to provide a heating chamber of reduced thickness, so that the heat transfer from the thin film heater to the consumable is optimized. In particular, the present invention allows the formed side wall of the tubular member to be controlled to 0.1 mm or less, preferably between 0.8 mm and 0.9 mm. The controlled low thickness also facilitates the installation of the heating chamber, especially installation via the circumferential planar lip 15, which is received in a corresponding recess in the body of the aerosol generating device 200. The method of the present invention allows the dimensions to be controlled to a minimum of 0.01 mm and angles of ±5°. The method also allows precise control of the shape of the protrusions, thereby allowing high geometric precision, in particular allowing very short radii, such as 0.1 to 0.2 mm radius of curvature in surface features. Thus, the method of the present invention provides a technique for manufacturing a heating chamber particularly suitable for use in an aerosol generating device, where precise control of the heating temperature is required to control the heating temperature within a specific window to provide effective aerosol release without overheating the consumable 210 or the material of the film heater or aerosol generating device 200.

10: Tubular components

11: Side wall

11t: Side wall thickness

12: Open end

13: Closed end

20: Tubular mold

21: Inner surface

22: Annular groove

23a: First movable mold part

23b: Second movable mold part

24: Open end

25: Closed end

31: Seals

32: Spray nozzle

33: External clamping element

34: Connection point

Claims (15)

A method for manufacturing a heating chamber for an aerosol generating device, the method comprising: providing a metal tubular member, the metal tubular member comprising a tubular side wall having an open end and an opposite closed end; the tubular side wall having a thickness of no more than 0.15 mm; inserting the tubular member into a tubular mold, the inner surface of the tubular mold having a shaped profile with at least one protrusion or recess; sealing the open end of the tubular member; and injecting a fluid into the tubular member under pressure to deform the tubular member outwardly so that the tubular member conforms to the shaped profile of the surrounding tubular mold. A method as claimed in claim 1, wherein the forming profile of the tubular mold includes an annular groove in the inner surface of the mold, the annular groove extending around the circumference of the tubular mold so that after the fluid is injected, the tubular component includes an annular flange. The method as described in claim 2, wherein the tubular mold comprises: a cylindrical body having an annular groove formed by a length segment of the cylindrical body having an inner diameter greater than the rest of the cylindrical body; so that the annular flange comprises a corresponding length segment of the tubular member having a diameter greater than the rest of the length of the tubular member. The method as described in claim 2 or claim 3 further includes cutting the tubular member through the annular flange to provide a tubular member of reduced length having an annular collar at the open end. The method as described in claim 3 further includes cutting the annular flange to provide a planar circumferential lip around the open end of the tubular member. The method as described in claim 1 further includes applying inward pressure on the outer surface of the tubular member when the fluid is injected into the tubular member under pressure to provide one or more inwardly extending protrusions on the inner surface of the tubular member. The method of claim 6, wherein applying the inward pressure comprises: when the fluid is injected into the tubular member under pressure, pressing a plurality of elongated ridges into the outer surface of the tubular member to provide a plurality of corresponding elongated protrusions running in a lengthwise direction on the inner surface of the tubular member, the protrusions being positioned around the circumference of the tubular member. A method as claimed in claim 6 or 7, wherein the inwardly applied pressure is provided by one or more movable parts of the tubular mold; and when the tubular member is inserted into the tubular mold and fluid is injected under pressure, the one or more inwardly extending protrusions are provided by applying inward pressure to one or more movable parts of the tubular mold. The method of claim 8, wherein the tubular mold includes a first movable portion and a second movable portion positioned at different positions along the length of the tubular mold, the method further comprising: applying an inward pressure to the first movable portion to provide a plurality of elongated protrusions running along the length direction on the inner surface of the tubular member; and applying an inward pressure to the second movable mold portion to provide a plurality of point-shaped protrusions periodically arranged around the circumference of the inner surface of the tubular member. The method as described in claim 1, wherein the step of providing a tubular member comprises: punching a metal sheet to provide a metal disc blank; and deep drawing the metal disc blank to form a tubular member having an open end and a closed end. The method of claim 10, wherein deep drawing the metal disc blank comprises: forming the metal disc blank into an initial metal cup; annealing under vacuum or inert gas; and deep drawing the initial metal cup into an elongated tubular cup having a reduced tubular wall thickness. A method as claimed in claim 10 or claim 11, wherein deep drawing is performed from the metal plate blank to provide a tubular member having a tubular wall having a side thickness of 0.05 mm to 0.1 mm, preferably 0.07 mm to 0.09 mm. A method as claimed in claim 10 or claim 11, wherein deep drawing is performed to provide a tubular member having an inner diameter less than 8 mm and a length greater than 30 mm. A method as claimed in claim 10 or claim 11, wherein the metal sheet has a thickness of 0.2 mm to 0.6 mm, and the deep drawing is performed to provide a tubular cup having a base wall with a thickness of 0.2 mm to 0.6 mm at the closed end. A heating chamber for an aerosol generating device, the heating chamber being manufactured by the method described in any one of claims 1 to 14.

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