FR2682289A1 - Heat or cold energy accumulator - Google Patents

Abstract

Heat or cold energy accumulator, comprising a casing within which a medium capable of storing heat or cold is arranged. According to the invention, the medium consists of a polyurethane or silicone gel with constant thickness in a very thin casing. Applications: in particular, heating the accumulator in a microwave oven for human or veterinary therapeutic uses.

Description

 ACCUMULATOR OF CALORIFIC OR REFRIGERATED ENERGY.

The present invention relates to a thermal energy accumulator intended in particular but not exclusively for human or veterinary therapeutic uses.

The effects of such accumulators constituted by a hot water bottle consisting of a sealed envelope filled with boiling water or a bladder filled with cold water and ice are well known in human or veterinary medicine.

But in these accumulators the restitution of heat or cold is done quickly so that their use is limited in time. The object of the present invention is to overcome this drawback.

According to the present invention, the heat energy accumulator intended to slowly restore the energy, positive or negative, stored is characterized in that it comprises an envelope inside which is included a crosslinked gel.

By positive or negative calorific energy will be understood heat or cold compared to a determined temperature, only the direction of conduction being modified.

According to another characteristic of the invention, the gel is formed by polymerization of polyurethane or silicone inside the envelope. The accumulator can thus be heated inside a microwave oven.

The invention lies in the fact that we have a crosslinked natural or synthetic gel, mixed with fillers or not, in a very flexible envelope. The envelope is necessary because one of the characteristics of the gel in general is to be sticky. In addition, the crosslinking of the original liquid components of the gel is easier in an envelope and does not require a release agent after crosslinking.

The shape of this accumulator can be round, flattened, flat, adapted, in the case of the very rapid heating mode in a household microwave oven, to the shape of the rotating base for a better distribution of the caloric absorption . This shape can be any or cut to the precise shape of a body region where the application is necessary, for example in the form of a band for specific use of frontal "cold bladder".

The simplest manufacturing process is as follows
Crosslinking (gelation) is done flat so as to obtain a uniform thickness by closing the pouring opening at the filling stop.

If the crosslinking is carried out in a vertical position, the shape of the envelope must be forced between two hard planes.

 In any case, it is necessary to monitor the crosslinking so that the thickness of the "wafer" is uniform. Because of the heating sought for this accumulator and the stresses exerted on the constituent product due to the use of a specific heating means: the microwave oven for household use.

In a microwave oven heat is produced inside of what needs to be heated. In a conventional oven the heat source heats by radiation and conduction at the same time, the air, the walls of the oven, the containers and finally the "gels".

In a microwave enclosure a generator emits electromagnetic waves, these "microwaves" do not diffuse any heat by themselves they are reflected on the metal of the walls of the oven passing through certain materials to penetrate into "gels", l pregnant remaining cold.

In fact microwaves penetrate molecules of fat, sugar and water (most foods contain 65 to 95% water), each change of direction of the alternating current causes the change of orientation of these molecules to very high speed (several million times per second) this results in friction of the molecules against each other resulting in a rise in temperature.

Foods with a high fat and sugar content cook faster than those with a high water content because they absorb energy faster and reach a higher temperature.

Microwaves only penetrate "gels" over a thickness of 2 to 3 cm. Beyond the propagation of heat takes place by conduction.

Furthermore, the denser the "gel" and the longer the temperature rise time.

A large, very thick volume can be heated in two batches, the cooking and reheating times being short.

 It is necessary to arrange the "gels" in the most effective way without excess thickness. Rest times must be provided, since the emission of microwaves interrupted the "gels" continue to heat up by conduction (the process of the rest times as such is to be neglected in our case the thickness of gel exceeding rarely 4 cm. Thanks to the reflections on the walls, wave absorption is done above and below) and nothing should hamper the radiation of the microwaves on the gel and especially not the envelope.

A good study of the reaction of materials to microwaves will allow us to make a choice.

a) the material is reflective when it does not leave
pass the microwaves but reflects them like a
mirror. All metals steel, copper, stainless steel, aluminum
are to be avoided.

b) the material is absorbent when it becomes the seat
of heat production as soon as it is subjected to
radiation, this is the case of "gels" but also of
certain materials such as porous earth (not pottery
enamelled) which are often prohibited except to maintain
some preparations warm and in the case of frost
fine charges (micronized clay for example larger
in grain) from these products that store
heat but with the drawback of absorbing a lot of it
suddenly and to require a significant contribution of
calories from the start.

c) the material is said to be transparent when it is permeable
in the microwave: this is the case for glass, ceramics,
earthenware, porcelain, certain materials
plastics, normal paper, parchment, nonwoven and
coated cardboard. Glass and vitrified materials resist
well and are then heated by
conduction. Wood as a container is to be avoided because
it dehydrates and splits and loaded, it releases
water vapor which would cause a gas phase
in the envelope without need.

The preferred absorbent material for the accumulator
will be a polyether urethane gel (polyurethane) or a
silicone gel (more expensive to buy and therefore priced
returns).

General heating means
1) contact oven on hot hearth, there are
heating by conduction of air,
walls, containers, supports and
the element to be heated;
2) in a "bain-marie" by contact with water;
3) in the microwave oven.

One of the advantages of this product even if only the means of heating in a conventional oven or in a "bain-marie" are used is that it does not produce liquid effusion of any consistency whatsoever if the envelope is punctured or the cap of the improperly closed envelope.

Means of refrigeration of the accumulator: air contact, support in a refrigerator, a freezer, a refrigerated room.

Operating modes of the accumulator: examples of operation with household means.

Hot absorption Gel restitution only - conduction
classic oven, conduction
water bath
- absorption
microwave gel + - transparent charge conduction conventional oven,
water bath
- microwave: conduction
absorption at the level
gel then heat up
loads by
gel conduction + - transparent charge conduction oven, water bath, + absorbent - gel absorption and
loads requires
too much intake: conduction
of energy (the charges
can turn out
expensive and difficult
to implement)
Cold absorption Restitution
Whatever the gel composition with or without a charge: conduction conduction
These polyurethane or silicone gel products retain the initial calorific state for a long time after heating or refrigeration. In addition, the addition of transparent fillers to the microwaves reduces the heating time in this type of oven and lowers the cost price by reducing the gel material, the fillers however having a very good capacity for accumulating calories. and frigories.

 The optimum thickness of the accumulator is 2 to 3 cm (sometimes 4 if necessary). In the case of direct heating in the microwave oven, the charges if they are transparent to the waves are heated by conduction: from the gel to the charge.

The gel is a viscoelastic polymer, for example of polyurethane or of silicones and does not contain an aqueous phase.

The gel should not be rigid (it can have the consistency of fat) so as to follow the contours of the surface of the body where the accumulator element is pressed.

The gel should show very little variation in its mechanical properties in the temperature range of - 30 to + 1000C.

Polyurethane gels withstand + 1700C, silicone gels with + 2000C. The density of the gel is close to 1.

The loads must not include products reflecting the microwaves. The proportion of fillers is defined as a function of the balance sought between the time of heating in the microwave, the heating of the gel itself and the consequent accumulation of heat by conduction in these fillers To pass 500 grams of pure polyurethane gel from 200C to 750C it takes about 2 minutes in a medium power microwave.

The very flexible envelope is preferably made of polyurethane (resistant to temperature variations) permeable to water vapor (so as among other things to eliminate that which was "trapped" during manufacture), with an optimal thickness of 50 microns, polyethylene could strictly be appropriate, these films have elongation capacities at break of 400 to 600%.

The charges in the accumulator exist for two reasons; decrease in the effective cost price but also two-step action in the accumulation of energy during heating in the microwave oven and restitution in one time by conduction. These fillers can be microbeads of hollow or preferably solid glass, of zirconium oxide, of vitreous aluminum silicate with an optimal diameter of 50 to 300 microns, with a density closest to that of the gel. but of very small diameter for the most homogeneous distribution possible in the gel before, during and after its crosslinking. Micronized fillers of colloidal silica or clay (absorbing microwaves) can be used but respecting the main mechanical properties of the gel.

The recommended loads in the dimensions 50 to 300 microns will be full of soda-lime glass (or glass more solid on impact during a mechanical strike) for reasons of cost but also for their transparency in the microwaves and therefore their ability to allow the absorption of heat and its storage in two stages by the accumulator during a heating using a microwave oven for household use.

This accumulator can be sterilized by dry or humid heat at 1200C.

Although having bacteriostatic properties, these gels can be loaded with bactericidal products.

The storage time of heat or cold by this charged or uncharged gel accumulator is greater than that of an aqueous product, such as hot water bottles or ice packs, by several hours. Although the gel without load generally has a density practically equal to that of water, this can be explained by the fact that the gel is less good conductor of heat and keeps it longer but also that during displacements the constituents remain in place while in a "hot water bottle" the water from the inside can come into contact with the outside wall very quickly and cool down.

The heating or refrigeration temperatures of the accumulator are conducted so as to respect these physical characteristics and the biological characteristics of the subject treated in the presence of this accumulator so as not to burn or "freeze". In addition, for this purpose, the accumulator can be slipped into an envelope made of more or less cheerful fabrics and better made of synthetic or natural fur of the crimped sheep type: therefore, the volume of air between the skin surface and the accumulator. is increased so as not to burn the skin and underlying tissue if the battery is very hot or very cold.

It is possible to identify and indicate the external temperature of the accumulator: by an adhesive, detached from a roll, for single use changing color at a certain degree of heat or cold defined in advance;
: by a fixed system if it is not too rigid temperature indicator whose color varies on a scale according to the temperature to which are exposed these systems exist on simple supports which one can stick on the envelope (in front or behind);
: by a fixed cookie indicating the degradation of the accumulator by heat, this for safety purposes, indeed, the domestic means of heat production are sufficiently powerful so that in certain cases of too high temperatures, the components can be degraded - By the cold there are less problems, the household means made available do not drop below 300C.

In case of cut of the envelope: the wound can be talcée.

The marking (not of the manufacturer, designation of the accumulator, specification, temperature indicators) can be done - either by screen printing on the envelope outside or at
inside (the letters being reversed on the face
screen-printed -readable in a mirror-); - either with a "non woven paper" inside plated on
the face when the gel is poured and then through the envelope; - either a marked adhesive that does not interfere with the properties
mechanical of the envelope glued to the outside or to
the interior.

 It goes without saying that many variants can be introduced, in particular by replacing technically equivalent means without going beyond the ambit of the invention.

Claims (4)

1. Accumulator of calorific energy intended to restore  slowly the energy, positive or negative, stored  characterized in that it comprises an envelope  inside which a crosslinked gel is included. 2. Accumulator according to claim 1, characterized in that  that the gel is formed by polymerization of  polyurethane or silicone inside the envelope. 3. Accumulator according to claim 1 or 2, characterized  in that it has a uniform thickness of a few  centimeters. 4. Accumulator according to one of claims 1 to 3,  characterized in that the gel includes fillers  consisting of balls with a diameter of 50 to  300 microns in glass, zirconium oxide, silicate  aluminum, colloidal silica or clay.