Heating chamber

Abstract

A method for manufacturing a heating chamber (100) of an aerosol generating device (200) includes the steps of providing a metal tubular member (10) including a tubular sidewall (11) having an open end (12), the tubular sidewall having a thickness not exceeding 0.15 mm, inserting the tubular member into a tubular mold (20) having a shaped cross-section with at least one protrusion (17, 19) or depression on its inner surface, sealing the open end of the tubular member, and injecting a liquid under pressure into the tubular member to deform the tubular member outwardly to conform to the shaped cross-section of the tubular mold into which it is inserted. Shaping the tubular member using liquid pressure allows the required side shape to be transferred to the tubular member with high precision while maintaining a chamber wall thickness of less than 0.15 mm for efficient heat transfer to consumables during use.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a heating chamber, and more particularly to a heating chamber for an aerosol generating device. [Background technology]

[0002] Heating chambers are commonly used in a wide variety of applications that require a means of storing heat and transferring the 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 electronic cigarettes and tobacco vapor products. Such devices heat a consumable type aerosol generating material within a heating chamber to produce a vapor that is inhaled by a user.

[0003] Heat chambers generally include a thermally conductive housing or shell that defines an interior volume for holding the consumable and an opening for receiving the consumable. An internal or external heater may be used to provide an elevated temperature to the heat chamber. Most commonly, such heat chambers are heated from the outside, with the thermally conductive shell conducting heat to the interior volume. One means of heating such heat chambers is with a thin film heater along the surface of the heat chamber to ensure efficient heating of the consumable received within the chamber.

[0004] Heat chambers often need to be formed into a specific shape to accommodate a particular type of consumable. The interior surface of the heat chamber may also need to have a specific cross-sectional shape to hold the consumable and efficiently transfer heat to the consumable. One problem with known methods of manufacturing such heat chambers is that it is difficult to precisely control the specific shape of the heat chamber while controlling the thickness of the heat chamber walls to ensure optimal heat transfer. In particular, known methods of manufacturing heat chambers are unable to both provide thin chamber walls that provide good thermal transfer through the heat chamber and control the shape of the heat chamber with high precision. In particular, it is difficult to form thin metal sheets as needed without damaging or creating weak points in the formed chamber. Known methods are also limited in the complexity of the shapes that can be provided in the cross-sectional shape of the heat chamber, which limits the extent to which it can be optimized for a particular application.

[0005] The present invention is intended to expand on the approach to addressing the above-mentioned problems by providing a method of manufacturing a heat chamber that allows the heat chamber to be precisely shaped to optimize it for a particular application while still providing a heat chamber of the thickness required to optimize heat transfer to the consumable. Summary of the Invention [Means for solving the problem]

[0006] According to a first aspect of the present invention, there is provided a method for manufacturing a heating chamber of an aerosol generating device, the method comprising the steps of providing a metal tubular member including a tubular sidewall having an open end and a closed end, the tubular sidewall having a thickness of 0.15 mm or less; inserting the tubular member into a tubular die, the inner surface of which has a shaped cross-section with at least one protrusion or depression; sealing the open end of the tubular member; and injecting a liquid under pressure into the tubular member to deform the tubular member outwardly to conform to the shaped cross-section of the tubular die into which it is inserted. By using hydraulic pressure to shape the tubular member, the required side profile can be transferred to the tubular member with high accuracy, while keeping the thickness of the chamber wall below 0.15 mm to achieve efficient heat transfer to consumables during use. Furthermore, the method of the present invention allows the transfer of more complex cross-sectional shapes to the heating element, which are difficult to achieve by known methods. By using hydraulic pressure and a tubular die, a much wider range of surface shapes can be transferred to the tubular member.

[0007] The steps of inserting a tubular member into a tubular mold and injecting liquid under pressure into the tubular member to outwardly deform the tubular member may be referred to collectively as the hydroforming step in the following disclosure.

[0008] The metal tubular member preferably comprises stainless steel. More preferably, the thickness of the tubular side wall is 0.1 mm or less, or more preferably between 0.07-0.09 mm. This allows efficient heat transfer through the side wall of the heating chamber to the consumables while maintaining sufficient structural stability. The tubular member has a closed end opposite the open end, preferably having a thickness of 0.2-0.6 mm at the closed end to provide additional structural rigidity to the heating chamber. In a possible embodiment, after the liquid injection step, the tubular member is cut perpendicularly along its length to provide two open ends for applications requiring a heating chamber with openings at both ends of the tubular member.

[0009] The hydraulic pressure is preferably provided by injected water at a pressure of up to 250 bar. The particular pressure used will depend on the particular material, thickness and shape to be transferred. The applied pressure may vary during the hydroforming process. The pressure required may be determined through routine experimentation or simulation of new materials exploration.

[0010] The tubular mould is preferably provided in two or more parts which are fixed together during injection of the liquid and separable to release the shaped tubular member.

[0011] Preferably, the shaped section of the tubular mould includes an annular groove on the inner surface of the mould, the annular groove extending around the periphery of the tubular mould such that after injection of the liquid, the tubular member includes an annular flange. In this way, precisely controlled dimensions can be provided for the annular flange. The annular flange can be used to precisely and reliably mount the heating chamber within the apparatus.

[0012] Preferably, the annular groove extends along the tubular die to provide a peripheral channel around the inner surface of the tubular die. In other words, the groove may have a substantial width in a direction corresponding to the longitudinal axis of the tubular member, for example a width of more than 1 mm, preferably more than 3 mm. The cross-sectional shape of the groove may be approximately rectangular, square, or trapezoidal.

[0013] Preferably, the tubular mould may comprise a tubular, preferably cylindrical, body. In a particularly preferred embodiment, the annular groove is formed by a section of the length of the tubular body having a larger inner diameter than the remainder of the tubular body, such that the annular flange comprises a section corresponding to the length of the tubular member having a larger diameter than the remainder of the length of the tubular member. In other words, the groove on the inner surface of the tubular mould has a depth that is suitably defined by the length of the side walls of the groove, which are substantially perpendicular to the inner surface of the tubular body. Preferably, the side walls of the annular groove are bounded by a base surface that is substantially perpendicular to the inner surface of the tubular body. Thus, both the annular groove of the tubular mould and the annular flange of the tubular member have a substantially rectangular cross-sectional shape. This shape is particularly advantageous for the further processing of the tubular member and for its mounting in the apparatus. For example, it allows the cylindrical lip to be formed in a straightforward manner by subsequent cutting of the annular flange.

[0014] The method may further comprise the step of cutting the tubular member through the annular flange to provide an annular collar at the open end of the shortened tubular member. In particular, the tubular member may be shortened by cutting the tubular member through the annular flange along its cross section, i.e. approximately perpendicular to the longitudinal axis. The annular collar around the open end is particularly useful for mounting the heating chamber in the device. The annular collar may be cut again to provide a peripheral flat lip around the open end. In particular, the annular collar may be shortened in radial length by cutting the annular collar in a direction approximately parallel to the longitudinal axis, such that the remaining lip is approximately flat and does not extend too far along the length of the tube. In other words, the annular collar may be modified to provide a peripheral flat lip. In an alternative method, the annular flange may be cut in one step to form the peripheral lip. The peripheral flat lip is particularly advantageous for precise and secure mounting of the heating chamber in the device. The term "lip" is used to refer to an annular extension that is approximately flat, i.e. has a depth in the direction of the tubular axis that corresponds to the thickness of the tubular member. The term "collar" is used to refer to the annular extension along the opening that is deeper in the direction of the tubular axis.

[0015] The method preferably further includes the step of applying an inward pressure to the outer surface of the tubular member to provide one or more inwardly extending protrusions on the inner surface of the tubular member. This may be performed by applying pressure to the outer surface with a pressing member, and the inward pressure may be applied during the liquid injection or in a separate step before or after hydroforming. For example, the tubular member formed and shaped during the liquid injection step may be internally supported, e.g., by a former and externally applied pressure, to generate one or more inwardly extending protrusions on the inner surface of the tubular member.

[0016] The method preferably includes the step of applying an inward pressure to the outer surface of the tubular member as the liquid is injected under pressure into the tubular member to provide one or more inwardly extending protrusions on the inner surface of the tubular member. In this way, positive and negative surface features can be provided on the surface of the tubular member in the same processing step, i.e. both protrusions and depressions can be on the outer surface of the tubular member (resulting in corresponding features on the inner surface of the tubular member). By injecting the liquid whilst providing an inward pressure, the surface features can be provided on the tubular member with greater precision. In particular, applying liquid pressure to a region of the inner surface of the tubular member with a pressure similar to that of the pressing member pressing against the outer surface of that region can cause the wall of the tubular member to more closely conform to the shape of the pressing member under application of the liquid pressure. This can provide the surface features with a high geometric precision, e.g. a radius of 0.1-0.2 mm.

[0017] When applying inward pressure to provide one or more inwardly extending protrusions, this can be achieved by pressing a plurality of elongated ridges against the outer surface of the tubular member to provide a plurality of corresponding elongated protrusions extending along the length of the inner surface of the tubular member, the protrusions being disposed along the circumference of the tubular member. The elongated ridges may be pressed against the outer surface such that as liquid is injected into the tubular member under pressure, the sidewall of the tubular member conforms more closely to the shape of the elongated ridges. The elongated ridges are preferably aligned with the longitudinal axis of the tubular member and may be configured to provide elongated protrusions extending along a central portion of the length of the inner surface of the tubular member. The elongated protrusions may be spaced apart from the base of the tubular member and from the open end of the tubular member. The elongated ridges may extend over approximately one third of the length of the tubular member. A plurality of elongated ridges may be provided on the inner surface of the tubular mold.

[0018] The step of applying inward pressure to 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 projections on the inner surface of the tubular member. The point projections may comprise a number of protrusions periodically arranged along the periphery of the inner surface of the tubular member. The point projections may be configured to improve grip of the substrate holder in the heating chamber while limiting heat transfer in this region. Each point projection may comprise a rounded projection, for example a part-spherical projection. The radius of the point projections may be between 0.05 mm and 0.25 mm, preferably between 0.1 and 0.2 mm. Other shapes of projections may also be formed in the method, for example truncated pyramidal projections, etc.

[0019] Preferably, the inwardly applied pressure is provided by one or more movable parts of a tubular mould and the one or more inwardly extending projections are provided by applying inward pressure by the one or more movable parts of the tubular mould when the tubular member is inserted into the tubular mould and liquid is injected under pressure. Preferably, the movable parts of the tubular mould are initially in contact with the outer surface of the tubular member and move radially inwardly relative to the outer surface to apply pressure as liquid is injected under pressure.

[0020] The tubular mold may include multiple movable parts. One or more of the movable parts may be configured to provide different types of inwardly extending protrusions. The movable parts may be movable together and / or independently to provide the different types of inwardly extending protrusions simultaneously or sequentially.

[0021] In one embodiment of the invention, the tubular die includes a first movable part configured to provide a plurality of elongated projections extending along the length of the inner surface of the tubular member and a second movable part configured to provide a plurality of point projections disposed along the periphery of the inner surface of the tubular member, the first and second movable parts being disposed at different locations along the tubular die, and the first and second movable parts may be configured to apply pressure simultaneously and / or sequentially.

[0022] The tubular mould may be configured to provide different penetration depths of the inwardly extending projections into the heated cavity. In particular, the movable part may be sized such that the penetration depth of the formed point projections is relatively smaller than the penetration depth of the formed elongated projections. This has the advantage of providing efficient gripping without excessive constraint on the stiff areas of the consumable that need to be gripped.

[0023] The inwardly applied pressure is preferably provided when a tubular member is inserted into a tubular mold and liquid is injected under pressure such that one or more inward protrusions and annular flanges are simultaneously formed, thereby providing an efficient method of forming the final shape of the heating chamber in one step.

[0024] The tubular member may be provided by punching a metal sheet to provide a plain metal disk and deep drawing the plain metal disk to form a tubular cup having an open end and a closed end. Deep drawing may include using a multi-stage deep drawing process to progressively draw the plain metal disk to increase the length of the tubular cup and reduce the thickness of its sidewall. An oil or soap may be used as a lubricant. The method may further include annealing the tubular member one or more times during and / or after deep drawing.

[0025] The method preferably includes forming a plain metal disk into an initial cup shape, annealing under vacuum or inert gas, and deep drawing the initial cup shape into a long narrow tubular cup while reducing the tubular wall thickness. The deep drawing process may include ironing the tubular cup to reduce the wall thickness. Because plastic deformation of the metal during the initial deep drawing may harden the metal making further processing of the metal difficult, an intermediate annealing step allows the initial cup shaped part to be deep drawn to increase its length while reducing the tubular wall thickness. A further annealing step may be performed prior to the hydroforming step (injection of liquid under pressure) to soften the tubular part to facilitate casting during hydroforming.

[0026] The initial formation of the initial metal cup can be performed by cutting a rolled plate from a strip of metal using multiple pressings, which is then formed into a mini-cup. The initial mini-cup is shallow and is therefore deep drawn in several steps to the required length (preferably after an intermediate annealing step) by using an ironing operation to reduce the wall thickness to within the required range.

[0027] Annealing is done in a low pressure vacuum furnace for e.g. 10 -2 ~10 -4 This may be done at a pressure of 10 ...

[0028] Preferably the deep drawing process is carried out to form a tubular cup with an internal diameter of less than 10 mm, preferably less than 8 mm, and a length of more than 30 mm. Deep drawing may provide tubular members with lengths of more than 50 mm, for example up to 65 mm. After the hydroforming step the tube may be cut to provide formed tubular members with lengths of 20-40 mm, preferably 25-35 mm.

[0029] Preferably, deep drawing is performed from a plain metal disk to provide a tubular cup having a tubular wall with a side wall thickness of 0.05-0.1 mm, more preferably 0.07-0.09 mm. Side wall thicknesses within these ranges allow for efficient heat transfer through the chamber to the consumables during use, as well as precise inwardly extending protrusions to allow subsequent hydroforming.

[0030] Deep drawing can be performed to provide a bottom wall of the tubular cup having a thickness of 0.2-0.6 mm, preferably 0.4 mm. In particular, the metal sheet has a thickness of 0.2-0.6 mm, preferably 0.4 mm, and the deep drawing process maintains this thickness as the base of the tubular member. By providing a closed end with an increased thickness relative to the side wall, the mechanical strength of the heating chamber is increased while maintaining the optimal heat transfer properties provided by the reduced side wall thickness.

[0031] Preferably, the deep drawing process provides a tubular member including a central recess on the outer surface of the closed end. In particular, the recess may be formed during the initial imprinting of a plain metal disk. The central recess of the closed end is preferably provided with a corresponding protrusion on the inner base surface of the tubular member. The central recess of the closed end may serve to mount the heating chamber in the device. It may also serve to control the insertion depth of the consumable into the device. For example, when used in an aerosol generating device, the consumable, when inserted, abuts against a protrusion on the inner base surface that 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. The central protrusion may also serve to conduct heat to the end of the consumable that is in contact with the protrusion during use.

[0032] The method may further include wrapping a thin film heater around an exterior surface of the tubular member.The method may further include disposing a temperature sensor at least partially within a recess in the exterior surface of the heating chamber.

[0033] In a further aspect of the present invention there is provided a heating chamber of an aerosol generation device manufactured by a method according to any preceding claim. In particular the aerosol generation device may comprise a heating chamber, a thin film heater wrapped around the heating chamber, a power source and control circuitry configured to controllably supply power to the thin film heater to heat the heating chamber. The heating chamber may be attached to the device by a peripheral lip of the heating chamber received in a corresponding recess in the aerosol generation device.

[0034] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings. [Brief description of the drawings]

[0035] [Figure 1A-1D] 1 illustrates a schematic diagram of a method for manufacturing a heating chamber of an aerosol generating device according to the present invention; [Diagram 2] 1 shows a schematic of a heating chamber constructed in accordance with the present invention; [Diagram 3] 1 shows a schematic diagram of a method for forming a metal blank disk for deep drawing. [Figure 4] 1 illustrates a schematic diagram of a method for forming a metal tubular member according to the present invention; [Diagram 5] 1 illustrates a schematic of an aerosol generating device incorporating a heating chamber manufactured using a method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] FIG. 1 shows a schematic diagram of a method for manufacturing a heated chamber 100 of an aerosol generating device. The method includes the steps of providing a metal tubular member 10, which is a tubular member having a tubular sidewall 11 with an open end 12 and an opposite closed end 13, as shown in FIG. 1A. The tubular sidewall 11 of the tubular member 10 has a sidewall thickness 11t of 0.15 mm or less. The tubular member 10 is inserted into a tubular mold 20, which includes an inner surface 21 presenting a shaped cross-section with at least one protrusion or depression 22. The open end 12 of the tubular mold is then sealed and liquid F is injected under pressure as shown in FIG. 1B, which causes the tubular member 10 to deform outwardly to conform to the shaped cross-section 21 of the overlying tubular mold 20. The method according to the invention allows for the formation of a shaped heated chamber 100 having a precisely controlled shaped cross-section while maintaining the thickness 11t of the thinned sidewall 11. Precise control of the shape and sidewall thickness 11t of the heating chamber 100 optimizes heat transfer through the chamber 100, ensuring improved heating of consumables received in the chamber 100 when used in an aerosol generation device. Additionally, precise control of the shaping of the heating chamber 10 sidewalls 11 allows the heating chamber 10 to be fitted into the aerosol generation device with precision and accuracy.

[0037] 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 includes a generally cylindrical body having a closed end 25 and an open end 24, and a sidewall thickness 11t of about 0.1 mm. As shown in FIGS. 1A and 1B, the tubular member 10 is inserted into the tubular die 20 such that the closed end 13 of the tubular member 10 abuts the closed end 25 of the tubular die 20. The tubular die 20 has an inner surface 21 with a shaped profile that is transferred to the outer surface of the tubular member 10. In the example of FIG. 1, the shaped profile includes an annular groove 22 that extends around the periphery of the inner surface 21 of the tubular die 20.

[0038] A liquid injection nozzle 32 is inserted into the open end 12 of the tubular member 10 as shown in Figures 1A and 1B, the open end 24 around the tubular nozzle 32 is sealed with a seal 31 as shown in Figure 1B, and liquid F is injected under pressure. The seal 31 is preferably disposed within the open end 12 of the tubular member and clamped in place, such as by an external clamping element 33, which presses the tubular member tightly against the seal 31 as shown in Figures 1A and 1B. This liquid injection process can be carried out by injecting water into the tubular member 10, applying pressure to the inner surface of the tubular member 10 to deform it outwardly to the shaped cross section of the inner surface 21 of the tubular mold 20. The applied pressure can be up to 250 bar, with the particular pressure selected depending on the particular requirements of the process, such as the material and thickness of the tubular member 10 and the shape to be applied to the tubular member 10.

[0039] As described above, the tubular die 20 includes a generally cylindrical body having an annular groove 22 disposed along the periphery of the inner surface 21 of the die. Thus, the tubular member 10 deforms outwardly under the applied hydraulic pressure F into the annular groove 22 to provide an annular flange 14 along the periphery of the tubular member 10. In this example, the tubular die 20 includes an annular groove 22 formed by a segment 22L of the length of the cylindrical body having an inner diameter D2 that is greater than the diameter D1 of the remainder of the cylindrical body. Thus, the annular flange 14 includes a segment corresponding to the length of the tubular member 10 having a diameter greater than the length of the remainder of the tubular member 10. The annular groove 14 has generally rectangular sides formed by two peripheral side walls 22a that extend away from the tubular body of the die in a direction generally perpendicular to the longitudinal axis of the die 20 and are joined by surfaces that are generally parallel to the longitudinal axis of the die 20.

[0040] After the high pressure liquid F is injected into the tubular member 10, the tubular member is shaped to provide a corresponding annular flange 14, as shown in Figure 1C, whose dimensions correspond to the inner surface of the annular groove 22 of the mold 20. In particular, the tubular member 10 has an annular protrusion having a square shaped cross section formed by a portion of the length 14L of the tubular member 10 having a larger diameter than the remainder of the cylindrical body.

[0041] The method includes the further step of providing additional surface features 17, 19 on the outer surface 11 of the tubular member 10 that form the shaped heating chamber 100 shown in Figure 1D. In particular, an inward pressure P can be applied to the outer surface of the tubular member 10 as liquid is injected into the tubular member 10 to provide one or more inwardly extending protrusions 17, 19 on the inner surface of the tubular member 10. These protrusions 17, 19 can be provided in many different ways by applying pressure P during or after the injection of the liquid F by the nozzle 32. Figure 1 shows a particularly preferred means for providing the internal protrusions 17, 19 using the movable portions 23a, 23b of the tubular mold 20.

[0042] As shown diagrammatically in Figures 1A and 1B, the tubular die 20 includes a first movable part 23a and a second movable part 23b, each of which is configured to apply pressures P1, P2 radially inwardly to the outer surface of the tubular member 10 during a hydroforming step to provide the surface features 17, 19 on the surface of the tubular member 10. The movable parts 23a and 23b are disposed against the outer surface of the tubular member during a liquid injection step and are moved inwardly to transfer the surface features 17, 19 to the tubular die 10. The application of pressures P1, P2 during the injection of liquid into the tubular member allows the protrusions 17, 19 to be precisely molded along the shaped inner surfaces of the movable elements 23a, 23b applying pressure P. In some instances, the nozzle 32 allows the liquid F to be directed specifically around the area where the pressure is applied, encouraging the outer surface of the tubular member 10 to closely conform to the shape of the press 23 to precisely mold the protrusions 17, 19. In some instances, the pressure can be varied, for example by selecting a nozzle with a particular diameter. By controlling the parameters of the liquid injection process, rounded surface features with very short radii and narrow protrusions can be created. Thus, the hydroforming technique shown in FIG. 1 allows the protrusions 17, 19 to be formed with a narrow sidewall thickness 11t and high geometric precision to improve heat transfer through the heating chamber 100 when used in an aerosol generating device.

[0043] In the example of FIG. 1, the first movable mold part 23a (which may include multiple element movable parts) includes an inner surface feature in the form of a plurality of elongated ridges periodically arranged along the inner surface periphery of the movable mold part 23a and aligned with the longitudinal axis of the tubular member 10. The first movable mold part 23a is movable to apply pressure P1 during the liquid injection step, as shown in FIG. 1B. After the liquid injection step, the first movable mold part 23a thus provides corresponding elongated projections 17 extending lengthwise along the inner surface of the tubular member 10, as shown in FIG. 1C. A plurality of such projections 17 are arranged along the inner surface periphery of the tubular member 10. The elongated projections 17 provide a number of functions, including limiting the insertion depth of a consumable contained within the chamber, providing air flow between the projections, and enhancing heat transfer to the consumable, as will be described in more detail below when the shaped heating chamber 100 is used in an aerosol generating device.

[0044] The tubular mold 20 of FIG. 1 also includes a second movable mold part 23b located along the tubular axis of the mold away from the first movable mold part 23a and near the annular recess 22. The second movable mold part 23b has an inner pressing surface shaped to provide a plurality of rounded point projections 19 arranged along the inner periphery of the tubular member. The second movable mold part 23b (which may include a plurality of movable parts, each configured to provide a single projection, for example) specifically has a pressing surface including a plurality of rounded protrusions arranged periodically along the periphery of the mold part 23b. The second movable mold part 23b is configured to apply a pressure P2 to the outer surface of the tubular member 10 during injection of the liquid to provide the projections 19 shown in FIG. 1C. The projections 19 adjacent the annular flange 14 provide additional gripping and positioning of the consumable received in the chamber 100.

[0045] The movable parts of the molds 23a, 23b can be used to apply corresponding pressures P1, P2 during the injection of the liquid so that the inward projections 17, 19 are formed simultaneously with the annular flange 14. Alternatively, pressure P can be applied after the initial formation in the annular flange 14, and in a separate forming step, pressures P1, P2 are applied to the outer surface of the tubular member 10 having the movable parts while the liquid is specifically directed to a portion of the inner surface of the tubular member 10 opposite the point of the outer surface to which pressure P is applied. For example, a specific liquid pressure optimized for each stage of the casting process can be selected, for example a different liquid pressure can be directed to form the projections 17, 19 than that which forms the annular flange. The movable mold parts 23a, 23b can be used simultaneously or sequentially to apply pressures P1, P2 to form the corresponding projections 17, 19.

[0046] Following the hydroforming step shown in Figures 1A and 1B, the shaped tubular member 10 is removed from the tubular mold 20 as shown in Figure 1C. In particular, the tubular mold 20 is provided in sections that are fixed together during the liquid injection step. For example, the tubular mold 20 may be split lengthwise into two sections that are connected along an interface that runs along the length of the mold at a connection point 34 as shown in Figures 1A and 1B. The sections of the tubular mold 20 are then opened to release the shaped tubular member 10 as shown in Figure 1C.

[0047] Further processing steps are performed on the reformed tubular member 10 shown in FIG. 1C to prepare it for use as a heating chamber 100. In particular, the tubular member 10 may then be cut through the annular flange 14 to provide a peripheral flat lip 15 around the open end 12 of the tubular member 10, as shown in FIG. 1D. This can be accomplished by first cutting the annular flange 14 radially along cutting line C1 to shorten the length of the tubular member 10, as shown in FIG. 1C. The tubular member 10 is then cut again in a direction parallel to the tubular axis through the side wall 14a of the annular flange 14 along cutting line C2. Straightening the annular flange 14 in this manner provides a flat peripheral lip 15 along the periphery of the open end 12 of the tubular member 10, as shown in FIG. 1D. The peripheral lip 15 is particularly useful for mounting the tubular member 10 when used as a heating chamber 100 in an aerosol generating device. The hydroforming method shown in Figures 1A-1D allows for precise thinning of the thickness 11t of the peripheral lip 15, thereby allowing for precise mounting of the heating chamber 100 within the aerosol generation device.

[0048] FIG. 2 shows a particularly suitable shaped heating chamber 100 formed using the process shown in FIG. 1. FIG. 2A shows a schematic side view of the shaped heating chamber 100, and FIGS. 2B and 2C show cross-sectional views taken along lines AA and BB in FIG. 2A. As described above, the tubular member 10 is shaped by the method of FIG. 1 to provide a number of features. First, the interior surface of the heating chamber 100 is provided with a series of raised elongated ridges 17 extending a length 17L along the central portion of the length of the heating chamber 100. In this example, the heating chamber is cut to a length of about 31 mm, with the elongated protrusions having a length 17L of about 12 mm and spaced from both ends 12, 13 of the chamber 100. As shown in the cross-sectional view of FIG. 2C, a plurality of such protrusions 17 are provided periodically around the circumference of the heating chamber 100, with the protrusions having a tightly curved, rounded cross-section with a radius of about 0.15 mm. In particular, four projections 17 may be provided spaced at 90° intervals along the periphery.

[0049] These protrusions 17 are positioned to press into the consumable received within the heating chamber 100 to improve heat transfer from the heating chamber 100 to the received consumable. The protrusions 17 also ensure that sufficient clearance is maintained between the protrusions to allow air to flow from the open side to the closed side. The protrusions 17 also serve to prevent further insertion of the consumable into the chamber 100 by limiting the distance the consumable can be inserted into the chamber, for example by abutting portions of the consumable that are raised and do not easily deform. This can ensure that the consumable is placed at the correct insertion depth within the chamber 100 by limiting further insertion after a rigid portion of the consumable contacts the tip of the protrusion.

[0050] Additional point projections 19 or "gripping projections" 19 are also provided around the periphery of the heating chamber 100 as shown in FIG. 2B. The gripping projections 19 may comprise the second movable mold part 23b as described above. Again, four gripping projections are angularly separated at 90° projection spacing. The gripping projections 19 may serve to grip and position the consumable within the heating chamber during use. As described above, the second movable mold part 23b is located at a predetermined distance from the annular recess 22 of the mold such that when the formed tubular member 10 is cut to size, the gripping projections 19 are provided at a predetermined distance from the open end 12 of the heating chamber 100. In a possible mode, the point projections 19 are omitted and only the elongated projections 17 are formed.

[0051] FIG. 2A also shows a peripheral flat lip 15 formed by cutting the annular flange 14 around the open end 12 of the chamber. As clearly shown in FIG. 2A, the peripheral lip 15 has a thin thickness 12t of about 0.07-0.09 mm corresponding to the thickness 11t of the remaining sidewall 11 of the chamber 100, which is advantageous when used to mount the heating chamber 100 in an aerosol generating device. The base of the heating chamber 100 has a thicker thickness 13t of about 0.4 mm, which may help provide structural stability to the heating chamber 100. The thickness 11t of the sidewall and the thickness 13t of the base may be set during the initial formation of the tubular member 10 prior to hydroforming, as described below with reference to FIGS. 3A-3C.

[0052] 3 shows an additional initial step in the manufacturing method of the heated chamber 100 to prepare the initial tubular member 10 for hydroforming. The process involves cutting a plain metal disk 41 from a metal sheet 40 as shown in FIGS. 3A and 3B, and then deep drawing the disk 41 into a tubular member 10 ready for hydroforming as shown in FIG.

[0053] In particular, a multi-stage press may be used to cut rolled plates 41 from a strip of metal 40 and form these into small cups 43, as shown in Figure 4A. This may be part of an automated process in which a roll of metal sheet 42 is perforated as shown in Figure 3B to provide initial metal blank disks 41, which are then pressed into initial short cups 42, as shown in Figure 4A. These may be cleaned and reduced, for example with paraffin, and then vacuum annealed. The cups 43 may then be deep drawn in multiple steps to form thin-walled tubes to form tubular members 10 for use in the method according to the invention. The intermediate annealing steps soften the metal, making it easier to deep draw the metal cups to the required length.

[0054] As shown in FIG. 4, the thickness 13t at the base remains approximately constant during the deep drawing process, while the thickness 11t of the sidewalls gradually decreases as the initial cup 43 is progressively drawn into the final tubular member 10. The initial thickness of the blank metal disk 41t is approximately 0.4 mm before it is progressively drawn as shown in FIG. 3C to reduce the wall thickness to less than 0.1 mm, and the thickness at the base remains 0.4 mm. To further reduce the sidewall thickness, an ironing process can be used as shown diagrammatically in FIGS. 4B-4D. The deep drawing process can provide a tubular cup having a tubular wall with a sidewall thickness of 0.07-0.09 mm. This thickness range can improve heat transfer through the heating chamber to heating consumables during use while maintaining a sufficiently mechanically stable structure.

[0055] The deep drawing process also provides a recess 18 in the base 13 of the tubular member 10. This may be advantageous for holding the consumable at the bottom while leaving a gap for entrapped air to flow through the end of the consumable. This may also be advantageous when mounting the heating chamber 100 to an aerosol generating device. Following the multi-stage deep drawing process, the tubular member can be annealed again using vacuum or inert gas. For example, the tubular cup formed by the initial deep drawing can be annealed in a low pressure vacuum furnace or inert gas furnace, for example at a pressure of 10-2 to 10-4 mbar. The reduction in pressure or inert gas protects the surface of the tubular cup against oxidation. Due to the plastic deformation of the metal during deep drawing, the tubular cup can become quite hard, which is resolved by the annealing step to make it easier to cast the tubular member during hydroforming. The resulting tubular member 10 can then be used in the hydroforming process shown in Figures 1A-1D to form a shaped heating chamber 100.

[0056] FIG. 5 shows a heating chamber 100 for use in an aerosol generating device 200 manufactured by the method of the present invention. In particular, the heating chamber 100 is mounted in an aerosol generating device having an open end 12 at one end of the device for receiving a consumable 210 to be heated to generate an aerosol for inhalation by a user. The heating chamber 100 is preferably wrapped around its exterior with a thin film heater 220 to heat the sidewalls and interior volume of the chamber. The thin film heater 210 is connected to a PCB 201 and a battery 202 to selectively provide power to the thin film heater to heat the chamber 100 to a controlled temperature. The thickness 11t of the tubular sidewall 11 of the heating chamber 100 can be precisely controlled and maintained at a thin thickness of 0.15 mm or less, thereby improving heat transfer from the thin film heater 220 to the interior volume of the chamber. Furthermore, the protrusions 17, 19 can be formed with high precision on the inner surface of the heating chamber 100 so that they do not extend so far as to impede insertion of the consumable 210 into the heating chamber 100, and the thickness and distance of the extension of the protrusions can be carefully controlled to provide the required grip and improve thermal conduction to the consumable 210.

[0057] The elongated projections 17 can be precisely positioned to engage the aerosol-generating portion 212 of the consumable 210 and contact the rigid portion 211 of the consumable 210 as it is inserted into the chamber 100, while holding the consumable 210 in place so that the aerosol-generating portion 212 is efficiently heated by the thin film heater 220, and to prevent further insertion of the consumable 210. The increased thickness 13t of the base 13 of the heating chamber 100 provides structural rigidity when the heating chamber 100 is used in a device. A central projection 18 on the base 13 of the heating chamber 100 contacts a surface of the consumable 210 to prevent further insertion and to allow an air flow path to be created around the exposed peripheral portion of the consumable 210 when received in the chamber 100.

[0058] The method according to the invention solves the important problem of ensuring precise control of the thickness of the heating chamber sidewalls to make the thickness of the heating chamber thin so that the thermal conduction from the thin film heater to the consumables is optimized. In particular, the invention allows the sidewalls after shaping of the tubular member to be controlled to 0.1 mm or less, preferably 0.8-0.9 mm. The controlled thin thickness also aids in the mounting of the heat chamber, especially via a peripheral flat lip 15 that is received in a corresponding recess in the body of the aerosol generating device 200. The method according to the invention allows for dimensional control down to a minimum of 0.01 mm and angles of ±5°. The invention also allows for high geometric precision, especially precise control of the shape of the protrusions allowing for very short radii, e.g. radii of curvature of surface features of 0.1-0.2 mm. The method according to the invention thus provides a technique for the manufacture of heating chambers particularly suitable for use in aerosol generating devices where precise control of the heating temperature is required to control the heating temperature within a specific window for efficient aerosol release without overheating the thin film heater or the consumables 210 or materials of the aerosol generating device 200.

Claims

1. 1. A method for manufacturing a heating chamber of an aerosol generating device, comprising: providing a metal tubular member including a tubular sidewall having an open end and an opposite closed end, the tubular sidewall having a thickness not exceeding 0.15 mm; inserting the tubular member into a tubular mold, the inner surface of the tubular mold having a shaped cross-section with at least one projection or depression; sealing an open end of the tubular member; The method includes the step of injecting liquid under pressure into the tubular member to cause the tubular member to deform outwardly to conform to a shaped cross section of the tubular mold into which it is inserted.

2. 2. The method of claim 1, wherein the shaped cross section of the tubular mold includes an annular groove on an inner surface of the mold, the annular groove extending around a periphery of the tubular mold such that after injection of the liquid, the tubular member includes an annular flange.

3. The tubular mold comprises: a cylindrical body, the annular groove being formed by a lengthwise segment of the cylindrical body having an inner diameter greater than a remainder of the cylindrical body, 3. The method of claim 2, wherein the annular flange includes a segment corresponding to a length of the tubular member having a larger diameter than the remainder of the length of the tubular member.

4. the step of cutting the tubular member through the annular flange to provide an annular collar at an open end of the shortened tubular member. The method according to claim 2 or 3.

5. 5. The method of claim 3 or 4, further comprising the step of cutting the annular flange to provide a flat peripheral lip around the open end of the tubular member.

6. applying an inward pressure to an outer surface of the tubular member as liquid 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 according to any one of claims 1 to 5.

7. applying inward pressure 7. The method of claim 6, further comprising the step of pressing a plurality of elongated ridges against an exterior surface of the tubular member to provide a plurality of corresponding elongated projections extending the length of an interior surface of the tubular member, the projections being disposed along a periphery of the tubular member as liquid is injected into the tubular member under pressure.

8. the inwardly applied pressure is provided by one or more moving parts of the tubular die; 8. The method of claim 6 or 7, wherein one or more inwardly extending protrusions are provided by applying inward pressure by one or more movable parts of the tubular mold when the tubular member is inserted into the tubular mold and liquid is injected under pressure.

9. The tubular mold includes a first movable portion and a second movable portion disposed at different positions along a length of the tubular mold, and the method further comprises: applying inward pressure with the first movable portion to provide a plurality of elongated projections extending along the length of an inner surface of the tubular member; 9. The method of claim 8, further comprising the step of exerting inward pressure with said second movable portion to provide a plurality of point projections periodically spaced along a periphery of the inner surface of said tubular member.

10. The step of providing a tubular member comprises: perforating a metal sheet to provide a blank metal disk; A method according to any one of claims 1 to 9, comprising deep drawing the plain metal disk to form the tubular member having an open end and a closed end.

11. The deep drawing of the plain metal disk comprises: forming the blank metal disk into an initial metal cup; Annealing under vacuum or inert gas; 11. The method of claim 10, including deep drawing the initial metal cup into an elongated tubular cup having a thin tubular wall thickness.

12. A method according to claim 10 or 11, wherein deep drawing is performed from said plain metal disc to provide a tubular member having a tubular wall with a side wall thickness of 0.05 to 0.1 mm, more preferably 0.07 to 0.09 mm.

13. A method according to any one of claims 10 to 12, wherein deep drawing is carried out to provide a tubular member having an internal diameter of less than 8 mm and a length of more than 30 mm.

14. A method according to any one of claims 10 to 13, wherein the metal sheet has a thickness of 0.2 to 0.6 mm and the deep drawing is carried out to provide a tubular cup having a base wall thickness at the closed end of 0.2 to 0.6 mm.

15. A heating chamber of an aerosol generating device manufactured by the method according to any one of claims 1 to 14.

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