WO2010068112A1

WO2010068112A1 - Stirrer

Info

Publication number: WO2010068112A1
Application number: PCT/NO2009/000422
Authority: WO
Inventors: Ellen Kathrine Lie; Marianne Bergan
Original assignee: EMTECH AS
Current assignee: EMTECH AS
Priority date: 2008-12-08
Filing date: 2009-12-08
Publication date: 2010-06-17
Anticipated expiration: 2011-06-08
Also published as: NO20085102L

Abstract

A stirring rod or stirrer for heating or cooling liquids without external supply of energy. The stirring rod can be used for heating or cooling food and beverages, e.g. baby food, in places without convenient access to kitchen utensils and/or electric power. The surface temperature can be adapted to the purpose. Embodiments wherein the change of temperature is achieved by chemical reactions, phase transitions, electrical heating elements and thermo electric elements are disclosed. In one disclosed embodiment, the stirring rod is switched between heating and cooling mode by means of a switch.

Description

STIRRER

This invention regards an apparatus for heating or cooling of liquids without external supply of energy, i.e. without energy being supplied from the outside.

BACKGROUND AND PRIOR ART

From time to time, there is a need to heat or cool liquid in places in which there is no convenient access to kitchen utensils or electric power.

A first example is the need to heat baby food outdoors or in a cafe or restaurant. On the beach and in the nature it may be prohibited to light a fire, and it is, to say the least, impractical to prepare a water bath with a cooking apparatus based on propane, butane, ethanol, paraffin, or some other combustible gas or liquid. An open flame, as well as the risk for spilling, may be problematic, in particular with small children present. In other locations, such as cafes and restaurants, one may in principle ask to have the food heated. However, this is problematic for both staff and other customers if a lot of people wishes to have children's food heated during a short period of time, e.g. around lunch.

Another example can be the need for heating soup, stew, coffee, tea or other food and beverage to backpackers, soldiers, rescue personnel and other people who from time to time needs hot food or drinks in remote locations. During long term operations, e.g. major forest fires, it is common practice to bring hot food and be- verages in thermo containers to locations near the personnel. In other situations, it may be impossible to bring out food for various reasons, or it may be difficult or impossible to establish a (field) kitchen within a reasonable distance. In such cases, it has been customary to use traditional cooking apparatus based on combustible gases or liquids in order to heat the food or beverage. In situations where time constraints or other circumstances make it difficult or impossible to prepare a cooking apparatus, this solution is also a problem. The result is often that one chooses to, or is forced to, refrain from hot food or beverage. This may affect the performance ability in general. A third example can be a desire or requirement to cool a medium. The medium may be a beverage one prefers or needs to enjoy when cooled, or it may be a coolant for use in acute treatment of e.g. burns or sport injuries.

SUMMARY OF THE INVENTION

A first objective of the present invention is, as mentioned initially, to cool or heat liquid in locations where there is no convenient access to kitchen utensils or electric power.

A second purpose is to provide an apparatus that is easy to use, also in situations where the user has limited time available, or reduced ability to perform the neces- sary steps.

These and other problems are solved according to the invention with an apparatus to stir liquids, which apparatus comprises at least one elongated sleeve, characterized in that chemically stored energy provided in at least one cavity within the apparatus is used to provide a temperature difference between the outer surface of the apparatus near a first end and the outer surface of the apparatus near a second end.

The apparatus, hereinafter the "stirrer", thus works without there being provided electric power via cables from e.g. a power outlet in a house or car. Further, it may be adapted to the purpose. For example, a stirrer for baby food become somewhat hotter than the desired temperature on the food, but not as hot that it may cause burns on children or adults who may come in contact with it. Such a stirrer can be adapted to become, for instance, 45-60⁰C on the hot surface. Another embodiment may have a surface temperature of 60-70⁰C on the hot surface for heating food or beverages for adults. A stirrer to cool beverages must be cooler along part of its surface in order to work as intended.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference to the drawings, wherein similar numerals refer to similar elements, and where: Figure 1 shows a partial cross section through an embodiment suitable for mixing two reactants;

Figure 2 shows a release mechanism in greater detail;

Figure 3 shows a partial cross section through an embodiment suitable for com- bustion processes;

Figure 4 shows a detail along the line A-A on figure 3;

Figure 5 shows a flexible embodiment;

Figure 6 is a schematic view of an electric circuit with a heating element;

Figures 7 and 8 shows the effect of opposite polarity on Peltier elements;

Figure 9 is a schematic view of a stirrer having an electric heating element;

Figures 10 and 11 show schematically an embodiment in heating and cooling mode.

DETAILED DESCRIPTION

The various embodiments of the stirrer comprise essentially a hollow body, where media storing energy are disposed. By exothermic or endothermic chemical reactions, phase transitions or other chemical or physical processes, this chemical energy is transformed to heat, which increases, respectively decreases, the surface temperature near the lower end of the stirrer. In use, one holds the upper end. Hence, the upper end is thermally insulated from reactions and processes in the cavity of the stirrer. The lower end conducts heat from the processes in the cavity to the surface of the stirrer as efficiently as possible.

The stirring contributes to effective heating or cooling. This can be illustrated by first imagining a heating element with a surface temperature T disposed in a medium with temperature T-i, which is to be increased to T₂. The element's surface temperature T > T₂ in this example. After a while, the temperature of the medium near the heating element will be closer to T, whereas the temperature at a distance r from the heating element still can have a lower temperature at or near T₁. Different temperature at different distances from the heating element is hereinafter called a temperature gradient.

By stirring the medium or liquid, a mixture is obtained having a smooth or uniform temperature equal to the mean temperature of the gradient, which in this case is lower than the gradient temperature in the medium close to a stationary heating element.

According to classical equations, the rate of heat exchange is proportional to the temperature difference between them. By stirring the medium to be heated, a somewhat lower temperature around the heating element is achieved. The in- creased difference in temperature hence increases the heat transport from the heating element to the surrounding medium. Hence, a heating stirrer will be able to transfer more energy per unit of time, i.e. have greater effect, than a similar stationary heating column.

Similarly, a temperature gradient occurs if a stationary cooling element with a sur- face temperature T < T₂ is placed in a medium or liquid with initial temperature Ti which is to be cooled to T₂. In this case, the heat moves from the medium to the cooling element. By moving the cooling element in the liquid or medium, a uniform temperature distribution having a mean temperature is achieved, which mean temperature is higher than the gradient temperature near a stationary cooling ele- ment. This also increases the temperature difference, leading to more effective heat transfer as in the example above. The difference is that the liquid or medium in this case is more effectively cooled rather than more effectively heated.

A stirrer being moved around in a medium to be heated or cooled thus can perform the work in a shorter time, i.e. it has a greater mean transfer of energy per time unit, or greater mean power. Another way to state this, is that a stirrer with lower power to heat or cool a medium as fast as when using a similar stationary element.

When the temperature is essentially equal all over the medium, it is also easier to determine if the medium, e.g. baby food, is heated to desired temperature. This can be used to provide the stirrer with a simple sensor (not shown in the figures), which can be connected to an alarm device to communicate when the desired temperature is achieved.

Another benefit of the invention is reduced risk of eruptive cooking, which otherwise can be a problem when heating viscous media like e.g. children's porridge or a canned dinner.

Yet another benefit, is that only the energy required to heat or cool the medium to be heated or cooled, rather than additional energy required to heat e.g. a water bath or the like, which otherwise is used to avoid eruptive bubble formation in e.g. children's porridge or canned goods.

Processes that can be used in the stirrer comprise, among others, chemical reactions, phase transitions and the Peltier effect. These are described in more detail in the following.

Chemical reactions

In exothermic reactions, the reacted or final substance has lower enthalpy than the initial reactants. Phase transitions from gas to liquid or from liquid to solid are thus examples of exothermic reactions. Phase transitions are more fully discussed below.

Other known examples of exothermic reactions are combinations of acid and metal at constant pressure and volume, wherein the resulting salt has lower inner energy than each of the acid and metal put together. The surplus energy is released as heat, which in this case can be used to heat the stirrer along part of its surface.

Combustion is an important type of exothermic reactions, which is more fully described with reference to Fig. 3 below.

Explosive reactions are examples to show that naive energy considerations are not sufficient to conclude that a small amount of energy will distribute energy to a greater mass. One example may be hydrogen peroxide, which is transformed to water and oxygen using silver as a catalyst (2H₂O₂ →_Ag 2H₂O + O₂). The reaction produces water and oxygen with a temperature of 700⁰C, and has been used in rocket motors since the nineteen sixties. Even if a small mass at 700⁰C could heat a larger mass to a lower temperature, the temperatures and pressures in the resulting system will pose practical requirements to a container which are hardly compatible with a stirring rod. The example above also illustrates that a metal can be used as a catalyst, i.e. that the metal is not a reactant or part of the final substance.

Endothermic reactions draw heat from the surroundings to create a combination having larger inner energy than the original reactants. Such reactions can be used to cool par of the surface of a stirring rod.

Selection of reactants depends on, among other things, desired temperature. It is further advantageous if the reactions are not poisonous or environmentally harmful. Cost of manufacture will of course also influence on the choice, e.g. id the stirrer has to be manufactured from special materials in order to withstand etching or corrosive materials or water at 700⁰C as described above. The reactants are not part of the invention. Use of enthalpy tables to select suitable reactants and compositions are presumed known for those skilled in the art.

Figure 1 shows a stirring rod having a hollow cylindrical body 1 with an internal separating wall 2, which separates the inner cavity in a lower chamber 3 and an upper chamber 4. A mechanical release mechanism, illustrated by a piston 5, breaks the separating wall when the stirring rod is activated. This leads to the reactants being mixed, and the stirring rod changes temperature along part of its surface.

In the embodiment shown in Fig 1 , the lower chamber 3 may be manufactured from light metal or another metal. The outer surface will typically be a plastic sleeve, an epoxy resin or some other material that can safely be put into food or beverages, and that prevents ions or molecules from leaving the chamber 3. The upper chamber 4 can prior to activation be filled with another reactant, e.g. an acid or base, suitable for reacting with the first reactant. In this embodiment, the length and localization of the metal tube determine which part of the stirring rod will be heated, both in that the metal is part of the reaction, and in that metals in general conduct heat well.

In a second embodiment, the wall of the chamber 3 may be a pipe made of light metal or metal which is coated on the inner side such that the metal tubing con- ducts heat, but does not take part in the reaction. The chamber 3 can still contain a suitable reactant like e.g. an alkaline metal, earth alkaline metal, light metal or metal reacting with an acid or a base.

In a third embodiment, the internal surface of the chamber 3 may be coated with a metal acting as a catalyst.

In a fourth embodiment, the wall of the chamber 3 may be made of non-metallic material, e.g. plastic, and the reactants do not need to comprise an alkaline metal, earth alkaline metal, light metal or other metal. Relatively thin walls will imply relatively fast heat transfer, even if the heat conductivity in a non-metallic sleeve can be lower than in a metallic sleeve.

A cooling stirring rod can in principle work like the heating stirring rod above, however with the difference that the reactants undergo an endothermic reaction when mixed.

Mechanical activation

Figure 2 shows a mechanical activation mechanism which in principle can break a separating wall between the chambers 3 and 4, whereby reactants are mixed and the temperature altering reaction begins. The activation mechanism in figure 2 comprises a circular membrane attached around its entire circumference and separates chamber 3 from chamber 4. A curved spring 6 is disposed over the membrane 2, and is provided with one or more needles 7 directed towards the membrane. A piston 5 is provided with a transport lock 9, preventing the piston from being depressed before the stirring rod is to be activated. When the stirrer is to be used, the transport lock 9 is first removed. Then the piston is pressed downwards. The user will feel increasing reaction from the spring 6 until it snaps over the plane defined by the point(s) of attachment, and which is perpendicular to the longitudinal central axis of the stirring rod. The needle 7 attached to the lower face of the spring thereby penetrates the membrane 2, such that the reactant(s) in chamber 4 is/are mixed with the reactant(s) in chamber 3. The user will feel the force from spring 6 suddenly disappear when the spring 6 snaps over, and thus get a tactile feedback on that the stirring rod is active.

It should be understood that a piston and a curved spring is one of many possible mechanisms for activation. A first alternative is a rotation between two parts of the stirring rod, whereby a helical groove or threads transform the rotation to an axial movement, which in turn may be used to penetrate a separating wall. A second alternative is bending of the stirring rod as indicated in Fig. 5.

A mechanism wherein an outer flexible body forms a first chamber 3 (not shown) that is bent until a second concentrically disposed chamber 4 (not shown) of glass or the like breaks is well known for a person skilled in the art, and will also be usable in this invention. When the glass ampoule breaks, the user gets a tactile feedback of the stirring rod being active.

Other mechanical movements, e.g. shaking, can also be used to activate the stirring rod.

It is also to be understood that the transport lock 9, which in Fig. 1 is shown as a partially cross-sectioned removable locking collar, can be provided in other ways known to one skilled in the art, e.g. in that the piston 5 must be rotated and/or axially displaced relative to the main body (sleeve) 1 before it can be used to activate the stirring rod.

Combustion processes

The term combustion processes as used herein, generally refers to exothermic re- actions where carbon (C) is combined with oxygen (O) to carbon monoxide (CO) or carbon dioxide (CO₂). Hence, possible processes include pyrolysis and other combustion processes. Oxygen can advantageously be provided as gaseous oxygen (O₂) from the ambient air. A suitable combustible (carbon source) is not part of the invention. Here is merely noted that a number of briquettes and other sources fro carbon based on alcohols and paraffines having from two to several tens of carbon atoms per molecule are commercially available, and that one skilled in the art is free to choose a source of carbon for the application at hand.

Figure 3 shows an embodiment wherein the substantially cylindrical body 1 comprises an upper part 8 and a lower part 9 connected by a threaded coupling 12. It should be understood that:

- other common means for connecting parts, like e.g. helical tracks, hinges and locking devices and various joins, can be used rather than threads;

- other embodiments can be provided with a similar connection, for example to provide a sales package having reduced length;

- the release mechanism in some embodiments can be combined with this function, .e.g. such that the stirring rod is activated when two parts are screwed together.

The stirring rod on Fig. 2 is further provided with openings 10 for air supply, and a combustion chamber 13 in the lower part of the stirring rod for disposal of a carbon source.

Prior to use, the two main parts are separated, the carbon source is disposed in the combustion chamber 13 and ignited, whereupon the two main parts are reconnected. The carbon source can alternatively be disposed in the combustion chamber 13 through an opening (not shown) in the sidewall of the apparatus, whereupon a lid is provided to close the opening.

Because the exhaust channel 11 , shown centrally in the embodiment on Fig. 3, is longer than the channels of the air intakes 10, air will be pulled in through the openings 10. The air is the pre heated on the outer side of the combustion chamber 13 before it flows into the combustion chamber 13 in the lower part of Fig. 3. The air flow through combustion chamber and exhaust channel 11 is illustrated by vertical arrows in Fig. 3. The horizontal arrows illustrate the heat flow out from the stirring rod.

We note in particular that it could or should be good thermal (metallic) contact between the combustion chamber 11 and the outer wall of the stirring rod. The inflowing air can for this reason flow in channels, and does not necessarily comprise a space between the combustion chamber 13 and the outer wall as might be apparent on Fig. 3.

Fig. 4 shows a plate, which, when in use, is disposed between the two main parts 8 and 9 (section A-A) in figure 3. The plate is provided with a central hole for the exhaust channel 11 and a plurality of openings along the edge giving access to the air ducts around the combustion chamber 13. In use, the air will thereby flow into the paper plane through the openings along the edge of the plate, while smoke and exhaust flow out of the paper plane through a channel 11 in communication with the central hole. The plate otherwise forms a covering over the combustion chamber, such that the air circulates in the intended manner.

Phase transitions

Phase transitions is a large, and to some extent complex class of chemical and physical processes. In this description, is suffices to state that phase transitions • from liquid to solid and from gas to liquid are exothermic (produce heat), and • from solid to liquid and from liquid to gas are endothermic (take up heat).

The explanation is that when the molecules in a solid are supplied with energy (heat), they will after a while move sufficiently that the bonds between the molecules break, and the composition transforms to liquid and thereafter gas. If, for example, a liquid is brought to crystallize, the excess energy will correspondingly be released as heat. This heat can be used to heat the lower part of the stirring rod. Conversely, if crystals are liquefied or liquid transforms to gas, the system needs heat supplied from the surroundings, which thereupon will be cooled.

Liquids crystallizing when e.g. a metal element is bent, are commercially available, and are used for, among other things, heat cushions and sports clothing. Suitable, known liquids are heated up to about 70⁰C at the phase transition. The process is reversible, such that the system returns to liquid phase when the crystals are heated, e.g. in that the system is heated in boiling water to 100⁰C, and thereupon is cooled to room temperature. The system is re-crystallized when the metal element is bent.

Figure 5 shows a stirring rod that is flexible along part of its length in order to activate this kind of compositions. As described above, such a flexible outer part can also be used to break an inner ampoule of e.g. glass, whereby two reactants are mixed.

A stirrer containing a suitable crystallizing liquid can if desired be used several times, e.g. by boiling between each use. When the crystals are supplied with heat during the boiling, the system returns to liquid phase, and remains in the liquid phase while the system is cooled to room temperature.

Other possible processes

In principle, any type of physical or chemical process resulting in transformation of energy to heat can be used. Before disclosing embodiments transforming chemically stored energy to heat vie electric power, we mention briefly the state equation for an ideal gas, which states that the relation pV/T, where p denotes pressure, V denotes volume, and T denotes temperature, is constant for an ideal gas. It is thus, at least in principle, possible to transform mechanical work via pressure or stored pressure to a heat difference in a heat machine or a reverse heat machine.

Embodiments using electrical batteries

The term "battery" as used herein means a device transforming chemically stored energy to electric current and voltage when the poles on the battery are coupled together through an electric circuit.

Figure 6 is a schematic view of a simple circuit wherein current from a battery 14 flows from the positive pole through a closed switch 16 and a heating element back to the negative pole of the battery. The electrical energy is transformed to heat in a heater filament or the like with a suitable electrical resistance R (Joule heating). This heat is illustrated with short, horizontal arrows in Fig. 6, and can in turn be transmitted to a part of a surface of a stirring rod as illustrated in Fig. 9.

The switch 16 may have a second, open position (indicated by a broken line near the top of figure 6), whereby no current flows in the circuit. The apparatus is then switched off.

The Peltier effect is also known as the Peltier-Seebeck effect and the thermoelectric effect. It can be used in the invention by an electric voltage over a material, hereafter the Peltier element, causes a temperature difference over the material. Hot and cool side changes when the polarity is switched. Peltier elements are commercially available, and can be delivered ready for installation in 'stacks' known as 'thermoelectric modules' adapted to desired temperature difference, heat capacity and other parameters. Such thermoelectric modules are shown schematically to the left in figures 7 and 8.

The figures 7 and 8 are intended to show that hot and cold side on a Peltier ele- ment, or a thermo electric modules change roles when the polarity over the element is altered. The two figures show two schematic illustrations of the same circuit, comprising a battery 14, a thermo electric module 15 and a switch 17.

In Fig. 7, the switch 17 is shown schematically in a first position giving a first polarity over the module 15. The resulting heat flow is illustrated by short horizontal arrows.

The switch 17 can have a second, open position indicated by a broken line near the top of figures 7 and 8) where no current flows in the circuit. The apparatus is then switched off.

In figure 8, the switch 17 is shown schematically in a third position giving a polarity over the module 15 being the opposite of the polarity shown in Fig. 7. This gives a heat flow in the opposite direction, as illustrated by short, horizontal arrows.

Figure 9 shows schematically an embodiment based on Joule-heating, where a battery 14 disposed in a cavity in the upper part of the stirring rod is connected to a heating element R in the lower part of the stirring rod. The upper part of the stirring rod is thermally insulated from its lower part, such that it is possible to hold the stirrer by its upper part and heat a medium with its lower part. The heat flow is illustrated by short horizontal arrows.

The heating element is heated because of its electric resistance, and may com- prise a filament or the like. A switch 16 can be used to switch on the stirring rod before use, and to switch it off when no longer in use. A schematic illustration of the coupling is shown in Fig. 6, and discussed above.

The heating element is, like in all the embodiments, thermally connected to the outer surface near the lower part of the apparatus. The heating element is at the same time electrically isolated from the outer faces of the apparatus. Batteries, switches, heating elements and their use are known to one skilled in the art. Hence, they are not further discussed here.

Figures 10 and 11 shows schematically an embodiment with elements and connections as shown in the figures 7 and 8 and described above.

Figures 10 and 11 shows schematically one and the same embodiment of the invention, where the switch 17 is in two different positions. This embodiment has three thermally separated sections: A lower section thermally insulated from a mid section, which in turn is thermally insulated from an upper section. In use, the user holds the upper section.

The lower section is thermally connected to a first side of a thermo electric module 15, and the mid section is thermally connected to the other side of the module 15. The thermo electric module 15 is electrically connected to a battery 14 through a switch 17, as shown schematically in Figs. 7 and 8, and discussed above. The battery 14 is, as in Fig. 6, schematically shown in a cavity in the upper section.

The flow of heat caused by the two positions of the switch 17 is shown by short, horizontal arrows. Hence, the lowermost section is heating in Fig. 10 and cooling in Fig. 11.

As mentioned in the description of figures 7 and 8, the switch 17 may also be switched to a position where no electric current flows between the battery 14 and the thermo electric element 15. In this case, no temperature difference is imposed between the two lowermost sections of the stirring rod, and the surface temperature on the lower and mid sections of the stirrer will approach, and after a while achieve, the ambient temperature.

It is noted that the figures are schematic, and that a number of known details are excluded for the sake of clarity. For example, the figures 6-11 show one battery in each figure. One skilled in the art will be able to use one or more batteries connected in series or in parallel, possibly with voltage dividers or other common circuit elements in order to provide desired current and voltage for a given embodiment. Hence, such elements are not depicted in detail.

One skilled in the art will also know how the switches 16 and 17 can be embodied in different implementation where an axial movement or relative rotation between a mechanical switch element and the main body 1 of the stirring rod can be used to switch the switches to different positions with functions as shown schematically in the figures 6-8.

The dimensions of the stirring rod are not specified. However, both smaller embodiments suitable for stirring small canisters of baby food and larger embodiments held by both hands and being suitable for stirring in larger vessels containing, e.g., food or beverages for several adults.

Claims

1. Apparatus to stir liquids, which apparatus comprises at least one elongated sleeve (1), characterized in that stored energy provided in at least one cavity within the apparatus is used to provide a temperature difference between the outer surface of the apparatus near a first end and the outer surface of the apparatus near a second end.

2. Apparatus according to claim 1 , characterized in that the sleeve (1) comprises at least two separate chambers (3, 4).

3. Apparatus according to claim 2, characterized in that the chambers (3, 4) contain separate reactants reacting with each other in an exothermic or endother- mic chemical reaction when brought together.

4. Apparatus according to claim 2, characterized in that the chambers (3, 4) contain gas having different pressures, and that the change of temperature is caused by a change of pressure and/or volume.

5. Apparatus according to claim 1 , characterized in that the apparatus comprises mechanical activation means (5).

6. Apparatus according to claim 1 , characterized in that the change of temperature is caused by a phase transition.

7. Apparatus according to claim 1 , characterized by means (6, 7, 4) causing a sudden change of force when the apparatus is activated.

8. Apparatus according to claim 1 , characterized in that the sleeve (1) comprises at least one air intake (10), and contains at least one combustion chamber (13) and at least one exhaust channel (11).

9. Apparatus according to claim 1 , characterized in that the sleeve (1) com- prises at least one battery (14) and at least one heating element with electrical resistance R.

10. Apparatus according to claim 1 , characterized in that the sleeve (1 ) comprises at least one battery (14) and at least one thermo electric element (15).

11. Apparatus according to claim 10, characterized in that the sleeve (1 ) further comprises a switch (17) adapted to switch between heating mode, a switched off condition and a cooling mode.

12. Apparatus according to claim 1 , characterized in that the sleeve (1) comprises a sensor and means to alert at a predetermined temperature.