In a conventional stationary shisha tobacco together with charcoal is burned and the generated hot smoke is guided through a water tank to cool the smoke. With the advent of electronic vapor devices or electronic cigarettes the behavior of a shisha should be obtained also at such portable devices. This requires guiding smoke or generally vapor through a small water tank for cooling down the vapor.

One problem of such a portable shisha is that the water tank is susceptible for leaking when the portable shisha is carried around, for example in a trouser pocket. This is because the shisha may adopt any possible orientation in space, when carried around, whereas in use the shisha is held in a generally upright position.

Further, the draft resistance for the smoke should not be negatively affected.

The prior art document US2815030A discloses a portable filter for cigarettes, cigars, smoking pipes and the like, the filter comprising a container which is adapted to hold without leakage a quantity of cooling fluid, such as water. The water is surrounding metallic tubes filled with tobacco smoke which is eventually inhaled by the user. The metallic tubes of this document are bend in a U-shape or multiple U-shapes to prevent that cooling fluid leaks from the container.

Other water filters for smoke are disclosed in the prior art documents DE10128432A1 and CN203538356U. In practice, however, the solutions of the prior art do not provide a high security against leaking or negatively affect the smoking draft resistance due to valves or the like for sealing the water tank.

It is therefore an object of the present invention to provide anelectronic cigarette water tank that has an increased protection against leaking and that does not negatively affect the draft resistance for the vapor to be inhaled. 3. Summary of the invention

The above-mentioned problem is solved by an electronic cigarette water tank, comprising a container for holding a liquid for filtering vapor from a vaporizer of an electronic cigarette, the container comprising an upper wall and a lower wall; an inhalation tube inside the container for releasing vapor from the water tank, wherein the inhalation tube having an upstream end located above a liquid level of the liquid within the container, when the water tank is in an upright position; a vapor tube inside the container for discharging vapor into the liquid, wherein the vapor tube having a downstream end located below a liquid level of the liquid within the container, when the water tank is in an upright position; wherein the inhalation tube having a substantially U-shape extending from the upstream end toward the lower wall of the container and turning back to the upper wall of the container; and wherein the vapor tube having a substantially U-shape extending from the downstream end toward the upper wall of the container and turning back to the lower wall of the container; wherein the inhalation tube and the vapor tube have hydrophobic properties.

Although the invention refers to a “electronic cigarette water tank” it should be understood, that instead of water other kinds of liquid maybe used within the electronic cigarette water tank, e.g. flavored or colored water-based liquids or the like. Further, it is noted that the electronic cigarette water tank can be a portable individual element or part of a portable electronic cigarette or portable shisha / shisha to go.

Due to the U-shape of both the vapor tube and the inhalation tube and the hydrophobic properties thereof a leaking of the water tank is excluded, since at least portions of the tubes are always above the liquid level regardless the orientation of the electronic cigarette water tank. Thus, it is unlikely that the liquid travels through the tubes against the gravity upwards to the respective upstream or downstream end. Further any mechanical components, like valves or the like are avoided, which would impact the vapor draft resistance and could be contaminated and cause-function disorders.

The hydrophobic properties of the vapor tube and the inhalation tube prevent or restrict ingress of water into the tubes or at least significantly lowers the water level within the respective tube. The hydrophobic properties of the tubes generate a high surface tension to the liquid, preferably water. This surface tension pushes the water out of the tubes to some extend and thus prevents leaking of the water tank in any possible orientation of the water tank.

Preferably, the downstream end of the vapor tube is located on a side of the electronic cigarette water tank that is opposite to the side of the upstream end of the inhalation tube.

Preferably, the inhalation tube and/or the vapor tube is/are made of a fluorocarbon resin material, preferably FEP, PTFE or PFA. Such materials are hydrophobic and suitable for a use with possibly hot vapor.

Preferably, wherein the inhalation tube and/or the vapor tube is/are coated with a fluorocarbon resin material, preferably FEP, PTFE or PFA. For the inhalation tube and the vapor tube also a non-hydrophobic base material can be used together with a coating of the tubes with a hydrophobic material. This surface-treatment also provides that the tubes are hydrophobic, but allows using a cheaper or better suitable base material. Preferably the base material of the vapor tube and the inhalation tube is a plastic material.

Preferably, the inner diameter of the inhalation tube and/ or the vapor tube is 3 mm or smaller, preferably 2,5 mm or smaller and more preferred 2 mm or smaller. Such inner diameters are particularly preferred as they provide a low vapor drag resistance and simultaneously lower the water ingress level within the hydrophobic tubes. Since the water ingress level within the hydrophobic tubes is lower with a smaller inner diameter of the tubes and the vapor drag resistance is lower with a larger inner diameter there is a trade-off between water tightness of the tank and vapor drag resistance, which is optimized by an inner diameter of the inhalation tube and/or the vapor tube of 3 mm or smaller, preferably 2,5 mm or smaller and more preferred 2 mm or smaller. Preferably, the container comprises an inhalation tube fitting at the upper wall, wherein the inhalation tube fitting is fluidly connected with a downstream end of the inhalation tube. The inhalation tube fitting allows an easy and tight assembly of the inhalation tube to the upper wall of the water tank. Preferably, the inhalation tube fitting is arranged to dispense vapor from the water tank to a mouthpiece. Thus, the inhalation tube is fluidly connected to the mouthpiece for dispensing cooled vapor.

Preferably, the container 10 comprises a vapor tube fitting at the lower wall, wherein the vapor tube fitting is fluidly connected with an upstream end of the vapor tube. The vapor tube fitting allows an easy and tight assembly of the vapor tube to the lower wall of the water tank.

Preferably, the vapor tube fitting is arranged to receive vapor from a vaporizer. Thus, the vapor tube is fluidly connected to the vaporizer to dispense vapor into the liquid within the water tank.

Preferably, the upper wall and/ or the lower wall can be opened for cleaning the inside of container.

Preferably, the electronic cigarette water tank further comprises a mouthpiece attached to the upper wall of the container, wherein the mouthpiece is inclined with respect to the vertical axis V of the portable water tank. This allows an ergonomic use of a shisha to go with the electronic cigarette water tank by the user.

Preferably, the mouthpiece points to the same side as the downstream end of the vapor tube and preferably opposite to the upstream end of the inhalation tube. This way, in operation it is guaranteed that position the downstream end of the vapor tube is under the liquid level. Further it is ensured that the upstream end of the inhalation tube is above the liquid level.

Preferably, the electronic cigarette water tank further comprises at the lower wall a connector for connecting the water tank to a vapor outlet of a vaporizer, wherein the lower connector is in fluid connection with the vapor tube. Preferably, the connector comprises a threaded connection, connectable to a standard vaporizer outlet.

Preferably, a shisha to go comprises a vaporizer for providing vapor and a electronic cigarette water tank as described above, for filtering the vapor from the vaporizer.

Preferably, the vaporizer is attached to the electronic cigarette water tank at the lower wall of the container. A method of filling an electronic cigarette water tank as described above preferably comprises the following steps: a. inserting the lower end of the electronic cigarette water tank into a liquid and sucking at the mouthpiece for filling the electronic cigarette water tank with the liquid until the liquid level in the electronic cigarette water tank has reached the desired liquid level; and b. subsequently removing the electronic cigarette water tank out of the liquid and further sucking at the mouthpiece, to remove liquid out of the vapor tube and to fill the vapor tube with air. A method of draining an electronic cigarette water tank as described above preferably comprises the following step: blowing into the mouthpiece for draining the electronic cigarette water tank from the liquid. For draining a short initial blow into the mouthpiece is enough. The container then empties itself due to the gravity of the liquid, preferably water. This is because the lower water outlet of the container, preferably formed by a vapor tube fitting in the lower wall, is arranged deeper than the water inlet, preferably formed by the upstream end of the vapor tube. 4. Short description of the drawings

In the following, preferred embodiments of the invention are disclosed by reference to the accompanying figure, in which shows:

Fig. 1: side sectional view of a preferred embodiment of an upper part of a shisha to go with a preferred embodiment of a electronic cigarette water tank.

5. Description of preferred embodiments In the following preferred embodiments of the invention are described with respect to the figure.

Fig. 1 shows a side sectional view of an upper part of a portable electronic cigarette / shisha to go too comprising a vaporizer 60 and a portable electronic cigarette water tank 1 attached to the vaporizer 60. Preferably the vaporizer 60 is a common vaporizer of an electric vaping device or a heat-not-burn electric cigarette. The vaporizer 60 generates vapor 62 that enters the water tank 1 and the vapor is filtered and cooled within the water tank. The water tank 1 comprises a container 10 for holding a liquid 40, preferably water. The container 10 comprises an upper wall 14 and a lower wall 14 and encloses a vapor tube 20 and an inhalation tube 30. The upper wall 14 of the container 10 can be opened to fill the liquid 40 into the container 10. In a different embodiment the container 10 may comprise a separate filling/draining opening (not shown). The vaporizer 60 is attached to the portable water tank 1 at the lower wall 12 of the container.

The vapor 62 generated by the vaporizer 60 enters the vapor tube 20, travels within the vapor tube 20 and already cools down to some extend and exits the vapor tube 20 into the liquid 40 as vapor 64. The vapor 64 then travels through the liquid 40 as bubbles 66 that raise to the liquid level 42. When doing so the vapor 64 further cools down and may be filtered to some extend by the liquid due to condensation. Then the vapor accumulates in vapor space 50 above the liquid level 42 within the container 10. From there the vapor 52 travels through the inhalation tube 30 to a mouthpiece 70 where the user can inhale the vapor 54. When travelling through the inhalation tube 30 the vapor 52 again cools further down to become vapor 54.

The inhalation tube 30 located inside the container 1 is for releasing vapor from the inside of the water tank. The inhalation tube 30 has an upstream end 32 that is located above a liquid level 42 of the liquid 40, when the water tank 1 is in an upright position, for example in the intended orientation for use. In the upright position the shisha to go too is generally held such that its vertical axis V is oriented upwards. As shown in Fig.

1, the inhalation tube 30 has a substantially U-shape and extends from the upstream end 32 toward the lower wall 12 of the container 10 and turning back to the upper wall 14 of the container 10. Thus, in the orientation for use the inhalation tube 30 allows a transport of vapor 52 that has accumulated above the liquid level 42 to the user. Such vapor 52 should be cooled down by the liquid 40 when travelling through the liquid 40 as vapor bubbles 66.

The vapor tube 20 inside the container 10 is for discharging vapor 64 coming from the vaporizer 60 into the liquid 40. The vapor tube 20 having a downstream end 24 located below a liquid level 42 of the liquid 40 within the container 10, when the water tank 1 is in an upright position, for example in the intended orientation for use. As shown in Fig. 1 the vapor tube 20 having a substantially U-shape extending from the downstream end

24 toward the upper wall 14 of the container 10 and turning back to the lower wall 12 of the container 10.

Both, the inhalation tube 30 and the vapor tube 20 have hydrophobic properties to prevent liquid 40 from entering into the tubes 20, 30. The inhalation tube 30 and/or the vapor tube 20 are preferably made out of made of a fluorocarbon resin material, preferably FEP, PTFE or PFA which are hydrophobic materials. However, it is also possible that the inhalation tube 30 and/ or the vapor tube 20 are only coated with fluorocarbon resin material, preferably FEP, PTFE or PFA. Thus, a cheap, non- hydrophobic base material for the tubes 20, 30 can be used, that obtains hydrophobic properties by the coating. Preferably, the inhalation tube 30 and the vapor tube 20 are made of the same material and have the same inner and outer diameter. Both, the hydrophobic properties of the tubes 20, 30 and their particular shape or arrangement with the container 10 ensures that the water tank 1 is leak proof. This allows to carry a shisha to go too with filled water 1 tank in any arbitrary position or orientation without the fear of leaking. Thus, in every possible orientation of the water tank 1 the possible liquid level 44 within vapor tube 40 and/ or the possible liquid level 46 within inhalation tube 30 is not more than some millimeters or a few centimeters.

The inner diameter of the inhalation tube 30 and/or the vapor tube 20 is less than 3 mm. Preferably the inner diameter can be preferably 2,5 mm or smaller and more preferred 2 mm or smaller. Thus, the tubes 20, 30 comprise an inner diameter that provides a sufficiently high throughput of vapor through the portable water tank 1, but is small enough to ensure the water tightness due to their hydrophobic properties. This avoids any additional elements like valves to be closed or the like which makes the smoking experience difficult. The outer diameter of the inhalation tube 30 and/or the vapor tube 20 is larger than the inner diameter and preferably is between 5 and 3 mm depending on the inner diameter.

The inhalation tube 30 is fluidly connected by its downstream end 34 to an inhalation tube fitting 28 at the upper wall 14 of the container 10. The inhalation tube fitting 28 is preferably a hollow nipple onto which the inhalation tube 30 is slid and held tight. To this end the inhalation tube fitting 28 comprises an outer diameter slightly larger than the inner diameter of the inhalation tube 30.

The hollow interior of the inhalation tube fitting 28 is fluidly connected to the mouthpiece 70 for dispensing vapor 54 to the user. The mouthpiece 70 comprises a socket 72 that mounts the mouthpiece to the container 10 inclined with respect to the vertical axis V. This facilitates the use of the shisha to go too when holding it in an upright position. The vapor tube 10 is fluidly connected by its upstream end 22 to a vapor tube fitting 16 at the lower wall 12 of the container 10. Like the inhalation tube fitting 28, the vapor tube fitting 28 is preferably a hollow nipple onto which the vapor tube 20 is slid and held tight. To this end the vapor tube fitting 16 comprises an outer diameter slightly larger than the inner diameter of the vapor tube 20. The vapor tube fitting 16 is arranged to receive vapor 62 from a vaporizer 60 attached to the water tank 1.

The upper wall 14 and/ or the lower wall 12 of the container 10 can be opened for cleaning the inside of container 10 if necessary. By opening the container 10 at one end it is also possible to clean or to replace the inhalation tube 30 and the vapor tube 20.

For connecting the water tank 1 to a vaporizer 60 the water tank 1 comprises at the lower wall 12 a vaporizer connector 15 that fits to a vapor outlet of a vaporizer 60. Preferably, the vapor outlet of the vaporizer 60 is standardized such that the vaporizer connector 15 fits to vapor outlets of different vaporizers 60. Preferably, the vaporizer connector 15 comprises a threaded connection such that thewater tank 1 can be connected to the vaporizer 60 by screwing. Further a friction fit connection between the vaporizer connector 15 and the vapor outlet of the vaporizer 60 is possible.

The water tank 1 further has a design such that it can be easily filled with liquid 40, usually water, by inserting the lower end of the water tank 1 into a liquid and sucking at the mouthpiece 70 and such that it can be easily drained from the liquid 40 by blowing into the mouthpiece 70.

For filling the water tank 1 the lower wall 12 thereof is held below a liquid level, for example into a glass of water. Then the user can easily suck at the mouthpiece 70 for sucking the liquid 40 through the vapor tube 20 into the container 10 of the water tank 1. The container 10 should be filled such that the liquid level 42 within the container 10 is about one third to the half of the height. Then the user takes the water tank 1 out of the water and sucks air into the vapor tube 20 for protection against automatic drain. The water tank 1 should then be dried at the outside thereof prior to connection to a vaporizer 60. After smoking or vaping the water tank 1 can be drained from the liquid inside by simply blowing into the mouthpiece 70. When doing so, the liquid 40 flows through the vapor tube 20 and the vapor tube fitting 16 out of the tank 1.

List of reference signs: 1 electronic cigarette water tank to container

12 lower wall

14 upper wall 15 vaporizer connector

16 vapor tube fitting

18 inhalation tube fitting

20 vapor tube

22 upstream end 24 downstream end

30 inhalation tube

32 upstream end

34 downstream end

40 liquid 42 liquid level

44 liquid level within vapor tube

46 liquid level within inhalation tube

50 vapor space

52, 54, 62, 64 vapor 60 vaporizer

66 vapor bubbles

70 mouthpiece

72 socket

100 electronic cigarette / shisha to go