HEATER ELEMENT, DEVICE PROVIDED THEREWITH AND METHOD FOR MANUFACTURING SUCH ELEMENT

Abstract

The present specification relates to heater element, device provided therewith and method for manufacturing such heater element. The heater element comprises a heater of a resistance heating metal that is provided in, at or close to a fluid path configured for heating fluid, wherein the heater comprises a conductor that is provided with a porous ceramic layer. In embodiments, the ceramic layer is provided on or at the conductor with plasma electrolytic oxidation. The ceramic layer has a thickness in the range of 5-300 μm.

Claims

1. A heater element for heating a fluid, comprising: a heater of a resistance heating metal that is provided in, at or close to a fluid path configured for heating fluid, wherein the heater comprises a conductor that is provided with a porous ceramic layer.

2. The heater element according to claim 1, wherein the ceramic layer is provided on or at the conductor with plasma electrolytic oxidation.

3. The heater element according to claim 1, wherein the ceramic layer has a thickness in the range of 5-300 μm.

4. The heater element according to claim 1, wherein the heater comprises a spiralled metal wire as the conductor, wherein the wire is provided with the ceramic layer.

5. The heater element according to claim 4, wherein the metal wire comprises titanium.

6. The heater element according to claim 4, wherein the spiralled heater has a central axis that is provided substantially in the longitudinal direction of the fluid path.

7. The heater element according to claim 1, wherein the ceramic layer is provided with a porosity.

8. The heater element according to claim 7, wherein the ceramic layer has a porosity in the range of 10-80%.

9. (canceled)

10. The heater element according to claim 1, wherein the conductor has a plate shape and is on one side provided with the ceramic layer, and wherein at least part of the metal layer has been removed.

11. A device comprising a heater element according to claim 1.

12. The according to claim 11, wherein the device is one of: a cooker for boiling liquid, an E-cigarette, a coffee machine, a knife, and an iron.

13. An insulated conductor comprising a metal conductor that is provided with a ceramic layer as an electrically insulating layer.

14. A method for manufacturing a heater element and/or device, the method comprising the steps of: providing a conductor of a resistance heating metal; and performing plasma electrolytic oxidation in a plasma electrolytic oxidation chamber to deposit a porous ceramic layer on the conductor.

15. The method according to claim 14, wherein the heater is configured to reach, in use, a temperature in the range of 50-750° C.

16. The method according to claim 14, further comprising the step of removing at least a part of the conductor material, wherein the conductor is shaped as a plate with on one side being provided with the porous ceramic layer.

17. The method according to claim 14, wherein after providing the ceramic layer on one side of the conductor, at least a part of the conductor material is removed with the use of electrochemical machining.

18. The method according to claim 15, further comprising the step of removing at least a part of the conductor material, wherein the conductor is shaped as a plate with on one side being provided with the porous ceramic layer.

19. The method according to claim 18, wherein after providing the porous ceramic layer on one side of the conductor, at least a part of the conductor material is removed with the use of electrochemical machining.

20. A method for heating a fluid, wherein: a heater of a resistance heating metal is provided in, at or close to a fluid path configured for heating fluid, wherein the heater comprises a conductor that is provided with a porous ceramic layer; wherein the porous ceramic layer is provided on or at the conductor with plasma electrolytic oxidation; wherein the heater comprises a spiralled metal wire as the conductor, wherein the wire is provided with the porous ceramic layer; and wherein the metal wire comprises titanium.

21. The device according to claim 11, further comprising a power increasing circuit configured for providing a power increase when the heater is switched on.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further advantages, features and details of the specification are elucidated on the basis of embodiments thereof wherein reference is made to the accompanying drawings, in which:

[0054] FIG. 1 A shows an E-cigarette provided with a heater element according to one embodiment of the specification;

[0055] FIG. 1 B shows a device provided with a heater element according to another embodiment of the specification;

[0056] FIG. 1 C shows a device provided with a heater element according to another embodiment of the specification;

[0057] FIG. 1 D shows a device provided with a heater element according to another embodiment of the specification;

[0058] FIG. 1 E shows a device provided with a heater element according to another embodiment of the specification;

[0059] FIG. 2 A shows a configuration of a heater element according to one embodiment of the specification;

[0060] FIG. 2 B shows a configuration of a heater element according to one embodiment of the specification;

[0061] FIG. 2 C shows a configuration of a heater element according to one embodiment of the specification;

[0062] FIG. 2 D shows a configuration of a heater element according to one embodiment of the specification;

[0063] FIG. 2 E shows a configuration of a heater element according to one embodiment of the specification;

[0064] FIG. 2 F shows a configuration of a heater element according to one embodiment of the specification;

[0065] FIG. 2 G shows a configuration of a heater element according to one embodiment of the specification;

[0066] FIG. 2 H shows a configuration of a heater element according to one embodiment of the specification;

[0067] FIG. 2 I shows a configuration of a heater element according to one embodiment of the specification;

[0068] FIG. 2 J shows a configuration of a heater element according to one embodiment of the specification;

[0069] FIG. 2 K shows a configuration of a heater element according to one embodiment of the specification;

[0070] FIG. 2 L shows a configuration of a heater element according to one embodiment of the specification;

[0071] FIG. 2 M shows a configuration of a heater element according to one embodiment of the specification;

[0072] FIG. 2 N shows a configuration of a heater element according to one embodiment of the specification;

[0073] FIG. 2 O shows a configuration of a heater element according to one embodiment of the specification;

[0074] FIG. 2 P shows a configuration of a heater element according to one embodiment of the specification;

[0075] FIG. 2 Q shows a configuration of a heater element according to one embodiment of the specification;

[0076] FIG. 2 R shows a configuration of a heater element according to one embodiment of the specification;

[0077] FIG. 2 S shows a configuration of a heater element according to one embodiment of the specification;

[0078] FIG. 2 T shows a configuration of a heater element according to one embodiment of the specification;

[0079] FIG. 2 U shows a configuration of a heater element according to one embodiment of the specification;

[0080] FIG. 2 V shows a configuration of a heater element according to one embodiment of the specification;

[0081] FIG. 3 A shows a setup of a plasma electrolytic oxidation chamber to produce an embodiment of a heater element described herein;

[0082] FIG. 3 B shows a cross section of the setup of the plasma electrolytic oxidation chamber of FIG. 3 A;

[0083] FIG. 4 shows the Voltage as function of time in the manufacturing of the heater element in the chamber of FIG. 3 A; and

[0084] FIG. 5 shows a heater element according to the specification.

DETAILED DESCRIPTION

[0085] E-cigarette 2 (FIG. 1A) comprises battery assembly 4 and atomizer assembly 6. In the illustrated embodiment atomizer assembly 6 is disposable. It will be understood that the specification can also be applied to systems with other configuration and that the illustrated embodiments are for exemplary purposes only. Details, including connections between components, that are known to the skilled person from conventional E-cigarettes have been omitted from the illustration to reduce the complexity of the drawing.

[0086] Battery assembly 4 comprises housing 8, (LED) indicator 10 with air inlet 12, air flow sensor 14, circuit 16 and battery 18. Air from inlet 12 is provided with air path 20 to sensor 14. Circuit 16 comprises an electronic circuit board that is connected to the relevant components of system 2. Battery 18 can be a rechargeable battery including the required connections to enable recharging. Battery assembly 4 has air inlets 22 and connector 24 to connect battery assembly to atomizer assembly 6.

[0087] Atomizer assembly 6 comprises housing 26 with air path 28 that is surrounded with buffer 30 comprising the E-liquid (for example a mixture of glycerol, propylene glycol, nicotine). Buffer material may include wicking material such as silica, cotton, etc.) or buffer 30 can be provided by other buffer means. In the illustrated embodiment heater element 32 is provided at or around the perimeter of air path 28. In one of the preferred embodiments heater element 32 comprises a wire of metallic titanium core 34 with ceramic titanium oxide layer 36 around metallic core 34. The E-liquid is absorbed and/or adsorbed in the porous ceramic layer. Wire 32 is heated by passing an electric current through metallic titanium core 34. Wire 32 is heated and the E-liquid is evaporated and/or atomized. The mixture is provided to outlet 38 of air path 28 at mouth piece 40.

[0088] Heater 32 achieves an improved temperature control and the ability to control the amount of E-liquid evaporating in time by varying the characteristics of the porous ceramic layer 36, such as thickness, size of pores, and porosity.

[0089] When inhaling at outlet 38 an under pressure in air paths 20, 28 is achieved. Air is sucked in through inlets 12, 22. Sensor 14 detects an air flow and circuit board 16 sends an indication signal to indicator 10. Battery 18 provides electricity to heater 32 that heats the E-liquid supplied from buffer 30 and vaporizes and/or atomizes the liquid such that a user may inhale the desired components therein.

[0090] In the illustrated embodiment heater 28 has its longitudinal axis substantially parallel to air path 28. It will be understood that other configurations are also possible in accordance with the specification.

[0091] Cooker 1002 (FIG. 1B) for boiling water comprises base station 1004 with feeder cable 1006. Container 1008 is connectable with connector 1010 to station 1004. Container 1008 comprises outlet 1012, cover 1014 that is connected with hinge 1016 to container 1004, and handle 1018. Cooker 1002 further comprises heater element 1020 capable of heating the water in container 1008. The surface of heater element 1020 is provided with ceramic layer having pores 1022. In use, pores 1022 act as initiators for bubbles when water is boiling. Preferably, in the plasma electrolytic oxidation pore size, distribution and variation of the ceramic layer of heater element 1020 is specified in accordance with the specification of the heater element's use.

[0092] Coffee machine 2002 (FIG. 1C) comprises housing 2004 provided with water reservoir 2006, cover 2008 that is hingedly connected with hinge 2010 to housing 2004, bean reservoir 2012 with bean cover 2014 and mill 2016, and coffee making unit 2018. Unit 2018 comprises heater element 2020, controller 2022, mixer 2024 and pressure pump 2026. Coffee is provided at outlet 2028. In embodiments heater element 2020 comprises a tube that on the inside is provided with the ceramic layer. This achieves a controllable heating process with reduced temperature variation as compared to conventional coffee machines.

[0093] Surgery knife 3002 (FIG. 1D) comprises handle 3004 and blade 3006. Blade 3006 is provided with a metallic core and a porous ceramic layer on at least part of its surface. Blade 3006 can be heated using energy from battery 3008 that is connected to blade 3006 with connector 3010. By providing blade 3006 that can be heated vessels, for example blood vessels, will be substantially closed by the heated blade. This reduces safety risks.

[0094] Iron 4002 (FIG. 1E) comprises heater 4004 that is shaped as a plate. Heater 4004 comprises partly removed metal layer 4006 and ceramic layer 4008. Optionally, in use, heater 4004 comes into direct contact with the clothing, for example.

[0095] Several embodiments of a heater element according to the specification will be illustrated. These embodiments can be applied to the earlier described devices and also to other devices.

[0096] Heater 42 (FIG. 2A) comprises a resistance heating material 44a as conductor and porous ceramic layer 44b. Heater 46 (FIG. 2B) is wound as a solenoid 48 (FIG. 2C) similar to heater 28 as illustrated in FIG. 1. In an alternative configuration heater 50 is configured as a toroid (FIG. 2D), or flat coil 51 (FIG. 2E), or flat spiral 52 (FIG. 2F), for example.

[0097] In the illustrated embodiment of system 2 buffer 30 is provided around air path 28 and heater 32 (see also FIG. 2G). In an alternative embodiment liquid reservoir 54 is provided inside the solenoid of heater 56 (FIG. 2H).

[0098] Further alternative configurations include heater 58 (FIG. 2I) wound as toroid structure with liquid inside toroid structure and air flow around toroid structure, and heater 60 (FIG. 2J) as a flat coil. Also, heater 62 (FIG. 2K) may comprise a layer of path of resistance heating material 64 as conductor on coated porous ceramic layer 66, or alternatively heater 68 may comprise a conductor layer 70 with coated porous ceramic elements or spots 72 provided thereon (FIG. 2L). Alternatively, heater 74 comprises conductor layer 76 and ceramic layer 78 (FIG. 2M), and optionally additional ceramic spots 80 (FIG. 2N). Another embodiment comprises porous ceramic layer 82 with conductor 84 wound in a spiral configuration (FIG. 2O).

[0099] Other embodiments include conductor tube 86 with static mixing form 86a coated with ceramic layer 88 (FIGS. 2P and 2Q). As a further alternative, conductor 90 is a tube (FIG. 2R) with a ceramic layer 92. Tube 90a can be filled with liquid on the inside and having air flow on the outside (FIG. 2S) or tube 90b has air flow on the inside and liquid buffer on the outside (FIG. 2T). Optionally, a ceramic layer is provided on the inside and the outside of tube 90. Also, tube 90 may comprise a number of smaller tubes or wires 94 with resistance heating material and ceramic material (FIG. 2U). A further alternative configuration (FIG. 2V) involves resistance heating metallic foam or sponge 96 coated with porous ceramic material 98.

[0100] The disclosed embodiments for heater 32 provide examples of heaters according to the specification that can be applied to systems 2.

[0101] Heater elements according to the specification are preferably manufactured using plasma electrolytic oxidation. As an example, for illustrative reasons only, below some manufacturing methods for some of the possible configurations for the heater element according to the specification will be disclosed.

[0102] In a first embodiment of the heater element, plasma electrolytic oxidation of titanium wire that is directly connected to an anode is performed.

[0103] For the plasma electrolytic oxidation use is made of a plasma electrolytic chamber 102 (FIG. 3 A). Work piece 104 is connected to the anode 106. Work piece 104 is clamped/fixed between two screws or clamps 108 that are connected to the ground/earth (anode 104) of a power supply. In the illustrated embodiment cathode 110 comprises stainless steel honeycomb electrode 112 that, in use, is placed at close distance above work piece 104. Electrolyte 114 flows between electrode 112 and anode 106, and effectively flows upwards through honeycomb electrode 112 together with the produced oxygen and hydrogen. Electrolyte effluent 116, together with the hydrogen and oxygen, is then cooled and optionally returned to chamber 102. In the illustrated embodiment the temperature of electrolyte 114 increases from around 11° C. entering plasma electrolytic oxidation chamber 102 to 25° C. exiting chamber 102 and is then cooled off using a heat exchanger (not shown).

[0104] In the illustrated chamber 102 two power supplies (Munk PSP family) are connected in series: one of 350 Volt and 40 Ampere and a second of 400 Volt and 7 Ampere resulting in a maximum of 750 Volt and 7 Ampere with resulting maximum power of 5.25 kW. The power supplies can be connected directly to anode 106 and cathode 110 resulting in direct current (DC) operation of the plasma. An optionally added switching circuit provides the option to operate the plasma with DC pulses. The frequency of the pulses can be set between DC and 1 kHz and different waveforms can be chosen (block, sine, or triangle). Plasma electrolytic oxidation is preferably performed in a pulsed current mode with a frequency (on-off) of about 1000 Hz, preferably with the current set at a fixed value and the voltage increases in time as a result of growing of the porous oxide layer. Current between 1 and 7 Ampere can be used to produce a ceramic layer.

[0105] To produce a heater element according to the specification, in chamber 102 titanium wire 202 (FIG. 3 B) is placed as work piece 104 on top of a titanium plate 204 that is connected to the stainless steel anode. Optionally, the anode is directly connected to wire 202. The electrolyte comprised 8 g/l NaSiO3*5H.sub.2O and 15 g/l (NaPO3).sub.6. Titanium wire is used made from titanium grade 1, with a diameter of 0.5 mm and 60 cm in length. The wire is coiled and connected to the anode. A potential higher than 500 volts is applied between the anode and cathode resulting in micro arc discharges on the surface of the titanium wire. On the surface of the wire, the metallic titanium is oxidized to titanium oxide with addition of silicates and phosphates from the electrolyte. The metallic layer is converted to a porous ceramic layer containing titanium oxides, phosphates and silicates. This results in a heater element 302 according to the specification.

[0106] Three experiments were done: 1) 0.5 Ampere for 15 minutes, 2) 1 Ampere for 15 minutes and 3) 2 Ampere for 15 minutes. The mass and diameter of the wire was measured before and after plasma electrolytic oxidation. The wire was placed in water for 5 minutes and the mass was measured as an indication of the amount of water adsorbed on the wire. The voltage as a function of time of the three different current settings can be seen in FIG. 4, and some further material information before and after oxidation is presented in Table 1.

TABLE-US-00001 TABLE 1 Material information Weight (mg) 1 2 3 Before PEO (mg) 525.49 529.82 After PEO (mg) 528.37 539.42 548.71 After heating (mg) 528.09 539.23 547.67 After 5 min in water 675.7 692.23 705.42 (mg) Thickness (μm) 36 71 113 Volume geads (ml) 0.15 0.15 0.16 Volume oxide layer 0.45 0.51 0.59 (ml) Porosity (%) 32.71 29.87 26.73

[0107] Ceramic wires were manufactured at different process conditions, including with 5 Ampere (wire 1) and 1 Ampere (wire 2) for processing time of an hour. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Thickness of ceramic layer porosity and adsorption of two ceramic titanium wires Time + Ceramic current thickness Porosity Adsorption Resistance Wire 1 1 hr @ 5 A 55 μm 45% 21 μl 1.4 Ω Wire 2 1 hr @ 1 A 30 μm 50% 13 μl 1.3 Ω
Wire 1: Before plasma electrolytic oxidation (PEO)
L=0.5 m, D=0.500 mm, R=1.2Ω, R.sub.calculated=2.44 Ω/m, Adsorption (water)=4 μl
Wire 1: After PEO (5 A for 60 minutes)
L=0.5 m, D=0.610 mm, R=1.3-1.4Ω, Adsorption (water)=21 μl, Porosity=44%

Wire 2: Before PEO:

[0108] L=0.5 m, D=0.500 mm, V=9.8 e−8 m.sup.3, m=4.2992 e−4 kg, ρ=4379 kg/m.sup.3
Wire 2: After PEO (1 A for 60 minutes)
L=0.5 m, D=0.5610 mm, V=1.236 e−8 m.sup.3, m=4.512 e−4 kg, ρ=3650 kg/m.sup.3, m.sub.oxide layer=2.13 e−5 kg, V.sub.oxide layer=2.56 e−8 m.sup.3, M.sub.estimate without porosity=4.452 e−5 kg, Porosity=50%, Calculated adsorption=12.8 μl

[0109] It will be understood that for alternative wires other conditions would apply. For example, for a wire having a diameter of 0.1 mm R.sub.calculated=61 Ω/m. Such wire with a length of 6.5 cm will give a resistance of 4Ω. With an oxide thickness of 100 μm an amount of 1.3 μl is adsorbed. 150 μm gives 3.1 μl and 200 μm gives 5.4 μl.

[0110] The experiments illustrate the manufacturing possibilities of the heater element for the system according to the present specification.

[0111] Further experiments have been conducted to produce other configurations for the heater. In one such further experiment a metal foil, preferably an aluminium foil, was used as starting material on which a porous metal (aluminium) oxide layer is provided, preferably in a plasma electrolytic chamber that is described earlier. Table 3 shows measured values of plasma electrolytic oxidation with constant current at 5 ampere for 9 minutes. Aluminium foil of 13 μm thickness was oxidized with a resulting thickness of aluminium oxide of 13 μm.

TABLE-US-00003 TABLE 3 Voltage, current, temperature of electrolyte going in the plasma electrolytic oxidation chamber (Tin) and going out the plasma electrolytic oxidation chamber (Teff) for constant current of 5 A. t min. Voltage V Current A Tin ° C. Teff ° C. 0.167 434 5 0.5 447 5 1 461 5 2 476 5 10.1 18.8 4 487 5 10.9 20.4 6 499 5 11.3 21.4 9 515 5

[0112] Table 4 shows the reproducibility of the process.

TABLE-US-00004 TABLE 4 Voltage, current, temperature of electrolyte going in the plasma electrolytic oxidation chamber (Tin) and going out the plasma electrolytic oxidation chamber (Teff) for constant current of 5 A. Voltage t min. V Current A Tin ° C. Teff ° C. 0.167 435 5 0.5 448 5 1 460 5 2 474 5 11.3 19.7 4 488 5 6 495 5 8 505 5

[0113] Table 5 shows the voltage and current for plasma electrolytic oxidation of aluminium foil at constant current of 2 A. Result was a 13 μm thick aluminium oxide layer.

TABLE-US-00005 TABLE 5 Voltage and current of plasma electrolytic oxidation with constant current of 2 A. t min. Voltage V Current A 1 380 2 2 415 2 3 429 2 4 437 2 5 443 2 6 448 2 7 452 2

[0114] Table 6 shows the voltage and current of the plasma electrolytic oxidation of aluminium foil with pulsed constant current of 1 kHz at 5 Ampere.

TABLE-US-00006 TABLE 6 Voltage and current of pulsed constant current of 1 kHz T min. Voltage V Current A 0.167 470 5 0.5 485 5 1 491 5 2 502 5 4 514 5 6 523 5

[0115] In a further experiment, plasma electrolytic oxidation was used to provide a porous, flexible and elastic ceramic layer of >70 μm on titanium foil. Plasma electrolytic oxidation grows a titanium oxide layer which is known to be ceramic (TiO.sub.2). Electrolyte was used with 8 g/l Na.sub.2SiO.sub.3*5H.sub.2O (Natrium metasilicate pentahydrate) and 15 g/l (NaPO.sub.3).sub.6 (Natrium hexametaphosphate). The electrolyte is pumped into the reaction chamber to act as the electrolyte and as a coolant. Titanium foil was used from titanium grade 2 with a thickness of 124 μm. In the manufacturing process the voltage increases as a function of time. This increase signifies an increased resistance and can possibly be explained by the growth of the titanium oxide (TiOx) layer. A thicker TiOx layer acts like an insulating layer between the metal and electrolyte. The resulting Voltage development in time can be seen in Table 7.

TABLE-US-00007 TABLE 7 Voltage and current as function of time for production of ceramic layer on titanium foil with plasma electrolytic oxidation Time min. Voltage V Current A 0.166667 435 6 0.5 510 6 1 540 6 2 551 6 3 553 6 4 554 6 5 556 6 6 556 6 7 557 6 10 557 6

[0116] The resulting foil structure can be processed further involving electrochemical machining. For example, use can be made of dissolution of Titanium grade 2 to make perfect squared shaped channels. With electrochemical machining (ECM) Titanium grade 2 is locally dissolved in a very controlled manner until the ceramic layer is reached. The finished result has to be well defined channels with squared edges and no residue on top of the ceramic layer. The ECM process is used with a cathode with the inverse shape of the product placed on top of a Titanium plate that serves as the anode. A potential is placed between the cathode and anode causing the anode to dissolve.

[0117] Electrolyte concentration is 5 M NaNO.sub.3. Current density can be varied from 20-150 A/cm.sup.2. The best results were realized with current densities of >60 A/cm.sup.2. Current is operated in a pulsed mode with the time the current is on and off can be varied. Best results were realized with on/off ratio of 16-80 and pulse on from 0.05 until 10 ms and pulse off from 1 ms until 160 ms. This additional processing step may also be applied to other configurations for the heater.

[0118] The above described experiments illustrate the possibility to manufacture the different configurations of the heater element and to implement such configuration in an E-cigarette, cooker, coffee machine and knife, for example.

[0119] The present specification is by no means limited to the above described embodiments thereof. The rights sought are defined by the following claims, wherein the scope of which many modifications can be envisaged.