Aerosol-Generating Device

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority to U.S. provisional application No. 63/656,743 filed Jun. 6, 2024, the contents of which are incorporated by reference herein in their entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure is directed to an aerosol-generating device. In particular, the present disclosure is directed to an aerosol-generating device that maximizes convective heat transfer therein.

2. Description of the Related Art

Typical aerosol-generating devices can deliver aerosol at undesirable temperatures and/or have undesirable physical dimensions.

In heated-tobacco products that use a cigarette-like consumable (e.g., long cylindrical shape that includes a filter), reducing the inhaled-aerosol temperature usually requires an additional cooling chamber inside the consumable. Such a structure increases the overall length of the consumable, and thus, increases the overall length of the heated-tobacco product. Otherwise, the length of the consumable's filter may be increased to reduce the inhaled-aerosol temperature, again with an undesired increase in length.

A similar problem occurs with other aerosol-generating devices, including heated-tobacco products that do not use cigarette-like consumables and aerosol-delivery devices.

The prior art devices either result in a higher inhaled-aerosol temperature, or reducing this temperature requires a solution that increases cost. For example, incorporating cooling units constructed from materials with advantageous thermal properties (e.g., high or low thermal conductivity) is more expensive. Alternatively, increasing the size of the device to accommodate larger consumables with marginally less-expensive cooling chambers increases costs.

These and other problems can be effectively resolved using the present disclosure. Furthermore, the present device can be implemented without incurring additional deleterious side effects, such as unacceptable increase in the operating temperature of the device.

Accordingly, there is a need for a device that overcomes, alleviates, and/or mitigates one or more of the aforementioned and other deleterious effects of prior devices.

SUMMARY

The present disclosure provides a handheld aerosol-generating device that substantially reduces the temperature of inhaled aerosol. Also, this device can result in a device of reduced size and/or improved overall performance.

The present disclosure provides such a handheld aerosol-generating device that has an electronic assembly that substantially reduces the temperature of inhaled aerosol by optimizing the length of the inner tube connecting the mouthpiece to the cavity of the oven chamber.

The present disclosure provides such an electronic assembly in the handheld aerosol-generating device that minimizes size by locating both the motherboard and the battery in the electronic assembly of the device.

The above and other objects, features, and advantages of the present disclosure will be apparent and understood by those skilled in the art from the following detailed description, drawings, and accompanying claims. As shown throughout the drawings, like reference numerals designate like or corresponding parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIG. 1s a side, cross-sectional view of an aerosol-generating device.

DETAILED DESCRIPTION OF THE DISCLOSURE

The FIGURE shows one example of an aerosol-generating device 100 of the present disclosure. Aerosol-generating device 100 has a mouthpiece 101, opening 102 that connects mouthpiece 101 to outer tube 104, inner tube 103, opening 105 that connects outer tube 104 to upper portion 106 of oven chamber, cavity 107 of oven chamber, lower portion 108 of oven chamber, electronic assembly 109, and device housing 110. The heat gradient shown in inner tube 103 in FIGURE provides an illustration of convective heat transfer as the fluid travels through inner tube 103 from the oven chamber cavity 107 to mouthpiece 101 where the temperature of the fluid, e.g., aerosol, decreases as the fluid transfers its heat through inner tube 103. Inner tube 103 in device housing 110 connects cavity 107 to mouthpiece 101 via airflow pathway 113. Electronic assembly 109 has a motherboard 111 and battery 112. Significantly, electronic assembly 109 locates the motherboard 111 and battery 112 in the aerosol-generating device 100, as discussed below to maximize the use of space in the in device 100.

Under the present disclosure, the shape of inner tube 103 and outer tube 104 need not be circular. Triangular tube shapes in fact would maximize space because its surface-area-to-area ratio would be the same as that of squares and circles, but with the advantage of having a smaller footprint. Thus, triangular tubes would maximize space that can be allocated to electronic assembly 109.

By locating the battery 112 and motherboard 111 in electronic assembly 109 and between the oven chamber cavity 107 on one end and the mouthpiece 101 on the opposite end, fluid transferred from the oven chamber cavity 107 to the mouthpiece 101 must pass through a longer tube, namely, inner tube 103, which is nested within outer tube 104. Increasing the length of inner tube 103 facilitates greater heat exchange before inhalation by the user.

The temperature of inhaled aerosol generated by an aerosol-generating device can pose a health risk to users. Increasing the length of the aerosol delivery distance between where the aerosol is generated and where the aerosol ultimately exits the device, mostly via inner tube 103, reduces the temperature of aerosol inhaled by the user and therefore mitigates the potential harm caused by inhaling aerosols above a certain temperature. This problem is of particular concern with dry herb (e.g., cannabis) vaporizers and heated-tobacco products that use a cigarette-like consumable.

Any concern about insulating electronic assembly 109 from the heat of generated aerosol are attenuated by the present device having inner tube 103 that distributes heat transfer over a larger area or length of travel.

This proposed electronic assembly 109 can be incorporated into an aerosol-generating device 100 either in lieu of or in addition to other heat transfer mechanisms such as baffles, heat sinks, secondary ventilation, and even cooling units and/or cooling chambers.

With the present disclosure, a single device can be used to generate aerosols from different inputs. For example, the active ingredients in tobacco and cannabis are released at different temperatures. Using the same device for generating aerosol from either tobacco or cannabis would result in different aerosols with distinct initial temperatures.

The space 115 between inner tube 103 and outer tube 104 acts as a thermal break or thermal barrier. Increasing the volume of this space 115 would improve the thermal management of both the inhaled aerosol and the other components inside electronic assembly 109 at the cost of reducing the space available for other components inside electronic assembly 109. This tradeoff is acceptable if it reduces the cost of inner tube 103 and outer tube 104; for example, by selecting less expensive materials for each. Also, the air in space 115 could then be ventilated through some exhaust port (not shown).

Likewise, adjustments can be made to the surface of inner tube 103 that directly impacts the effort required by the user to inhale a given volume of aerosol and/or the volume of aerosol inhaled per second by a user. Also, the composition of the inhaled aerosol (e.g., the proportion of active ingredients in a fixed volume of inhaled aerosol) can be affected. As such, the increased flexibility provided by the electronic assembly 109, and thus device 100, offers consumers the opportunity to customize the device 109 to achieve desired sensory experience.

The present device would improve device performance and, potentially, reduce the device's overall dimensions and overall cost. As such, this present device offers a way to reduce the overall dimensions of aerosol-generating devices and improve performance.

Most aerosol-generating devices are assumed to have a fixed size (i.e., dimensions are practically unchangeable). However, by delivering aerosol at a lower temperature, the present device improves performance, even while reducing its size. This improved performance may not be limited to reductions in the inhaled aerosol temperature, and can also extend to improvements in device efficiency or performance thereby result in a device that is preferred by consumers.

The present disclosure derives optimal values for its key components (e.g., the length, width, shape, and/or thickness of inner tube 103) from a general formula for convective heat transfer:

q = h · A · Δ ⁢ T

• • Where:
  • q is the heat transfer rate, measured in watts (W).
  • h is the convection heat transfer coefficient, measured in watts per squared meters per kelvin (W/m²·K).
  • A is the surface area of the tube, through which heat is being transferred, measured in squared meters (m²).
  • ΔT is the temperature difference between the fluid and the tube's surface, measured in kelvin (K).

The convective heat transfer coefficient (h) can be determined empirically. For a mixture similar to the one considered here (e.g., composed of propylene glycol and vegetable glycerin), one would need to know the specific heat, density, viscosity, and thermal conductivity of the mixture at the given temperature to calculate h. The same for materials used to construct, for example outer tube 104, except that the convective heat transfer coefficient of outer tube 104 can be modified by adjusting its thickness.

Generally speaking, because the thickness of a given material is inversely related to its heat-transfer coefficient (h), to maximize the thermal conductivity of inner tube 103 and minimize the thermal conductivity of outer tube 104 is achieved by decreasing the thickness of inner tube 103 and increasing the thickness of outer tube 104. Please note that maximizing the thermal conductivity of inner tube 103, which is equivalent to maximizing its convective heat transfer coefficient (h), increases the heat transfer rate (q) from the generated aerosol to inner tube 103, and thus, reduces the inhaled-aerosol temperature.

Once the heat transfer rate (q) has been calculated, the temperature decrease of the fluid per distance traveled through the tube using energy balance can be achieved. The energy balance equation for a differential length of the tube is given by:

ρ · V · c p · dT dx = - q

• • Where:
  • ρ is the density of the fluid, measured in kilograms per cubed meters (kg/m³).
  • V is the volume flow rate, measured in cubed meters per second (m³/s).
  • c_p is the specific heat capacity of the fluid, measured in joule per kilogram per kelvin (J/kg·K).
  • dT/dx is the rate of temperature change with respect to the tube length, measured in kelvin per meter (K/m).
  • q is the heat transfer rate, measured in watts (W).

By integrating this equation over the length of the tube, one can find the temperature profile of the fluid. For a small enough length, one can approximate the temperature decrease per millimeter (for example) by rearranging the equation to solve for dT/dx, and then converting the units to millimeters.

Given this temperature profile, the optimal length of inner tube 103 is the shortest length that reduces the inhaled-aerosol temperature below a threshold that is likely known in advance.

The preferred embodiment can be replicated. For example, these same equations can be used to derive optimal values for the width and/or shape (of inner tube 103 and outer tube 104), both of which correspond to the cross-sectional surface area. To the extent that space 115 between inner tube 103 and outer tube 104 impacts the convection heat transfer coefficient of each, the same is true for deriving the optimal volume of space 115.

The present handheld aerosol-generating device substantially reduces the temperature of inhaled aerosol even though the final dimensions of the structure is or can be the same as prior art devices. This is achieved by locating the battery 112 and motherboard 111 between the oven chamber 107 and mouthpiece 103, that in turn results in the inhaled aerosol having a substantially lower temperature. In other words, the present handheld aerosol-generating device 100 of the present disclosure maximizes cooling within limited size constraints. Further, device 100 can be incorporated with other heat reduction mechanisms.