DE29921341U1 - Heating pad - Google Patents

Description

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02 December 1999

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DESCRIPTION

Heat pad

The invention relates to a heat pad that is filled with a supercoolable, aqueous sodium acetate solution. A metallic body is located in this solution. By rubbing this metallic body against another metallic part of the heat pad, or by rubbing several such metallic bodies against each other, the crystallization of the sodium acetate solution in the supercooled state can be triggered. The crystallization takes place in an exothermic process. The contents of the pad are converted from their liquid to their solid state. This releases thermal energy that can heat the contents of the heat pad and thus the heat pad itself to over 50° Celsius over several hours.

Such heat pads and the physical heating principle underlying them have been known for a long time. For example, it is already known from DE-PS 149 151 that the necessary crystallization can be brought about with the help of a spring protruding into the solution.

A heat pad in the form of a compress is known from DE-PS 135 639. To activate it, several bodies are required which must be rubbed together to trigger the exothermic process.

The aforementioned DE-PS 149 151 already mentions that crystallization and thus the exothermic process cannot be triggered reliably in every case. On the other hand, however, crystallization must also be prevented from occurring too easily and thus unintentionally.

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In order to meet these conflicting requirements, a wide variety of trigger modifications have become known in recent years.

From WO 87/01275 it is known to use two metal bodies in the form of two nested helical coils as triggers. To trigger the exothermic process, the two coils are rubbed against each other, which is achieved by bending the double coil. The 4fc 10 rubbing of two bodies against each other facilitates the triggering process. However, this has the disadvantage that such a trigger can very easily activate itself unintentionally.

This risk of unintentional triggering is hardly to be feared with the trigger known from WO 89/10520; rather, this trigger is disproportionately difficult to trigger because a metallic spring is embedded in a two-part, relatively rigid housing.

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Finally, DE 40 32 144 A1 discloses a trigger for a heat pad, which achieves reliable triggering and yet effectively prevents accidental triggering. This trigger consists of a braid. The braid has the advantage that its individual "threads" rub against each other sufficiently strongly even when the braid is slightly bent, thus causing the exothermic process to be triggered safely. To protect against accidental triggering, this braid is loosely inserted in a two-part housing consisting of a cover and a base. The housing must be deformed accordingly to trigger. However, the braid can also consist of a rope or a strand that is suspended from a plastic tube.

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In addition, plastic caps can be placed on the ends of the rope or strand to prevent the fine metallic wires of the rope or strand from damaging the heat pad, which is generally made of plastic.

Based on this previously known state of the art, the invention is based on the object of specifying a heat pad of the type mentioned at the beginning which can be produced as economically as possible and whose trigger functions easily and safely.

This invention is given by the features of claim 1. The trigger of the heat pad has the following features, which in combination fulfill the above task. The body consists of only a single spiral. Such a spiral has a sufficiently smooth surface so that there is no risk of damage to the pad cover.

Nevertheless, the screw coil is provided with a tightly fitting plastic cover, which greatly reduces the risk of accidental activation. Recesses in the plastic cover ensure that the aqueous solution in the heat pad can come into contact with the coil.

Designs of the trigger for such a heat pad are specified in the subclaims. The cover can surround the coil like a tube. To prevent the free ends of the coil from damaging the cushion cover, the cover can extend beyond the respective free ends of the coil in the direction of the coil's longitudinal axis. It is then not the coil and thus a metal part that can hit the bag wall, but only the cover.

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A coating that extends beyond the free ends of the coil can also encompass these free ends. This encompassing can be done in such a way that, for example, a central opening in the longitudinal axis of the coil remains free, allowing the aqueous solution to pass through into the interior of the coil. On the other hand, the front side of the coil can also be completely encompassed by the coating, thus creating a completely closed coating plate instead of the coating ring disk present in the front area of the coil. In order to allow the aqueous solution to enter the interior of the coil, openings for the liquid must then be provided in the area of the jacket coating or in the area of the other front plate.

Further features and advantages of the invention result from the features further listed in the claims and from the following embodiments.

The invention is described and explained in more detail below with reference to the embodiments shown in the drawing. They show:

Fig. 1 is a view of a heat pad according to the invention with a first embodiment for a trigger,

Fig. 2 is a longitudinal section through the trigger according to Fig. 1,

Fig. 3 is a view along the line 3-3 of Fig. 2, 30

Fig. 4 is a view taken along line 4-4 of Fig. 2,

Fig. 5 a longitudinal section through a second embodiment

for a trigger according to the invention. 35

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A heat pad 10 consists of two plastic sheets that are joined together with a circumferential weld or sealing seam 12 (Fig. 1). In one edge area there is a widened seam section 12.2 that runs into the interior of the pad 10 in some areas. In this seam section 12.2 there is a recess 18 designed as a handle hole or hanging eyelet.

The interior of the heat pad 10 is filled with an aqueous solution 20, which consists, for example, of sodium acetate.

A trigger 22 floats in the solution 20. Bending this trigger 22 causes its metallic surfaces to rub against each other, causing crystallization of the sodium acetate solution in the supercooled state. The heat released during this crystallization heats up the solution 20 and thus the heat pad 10.

The trigger 22 consists of a metallic coil 24.

In the embodiment according to Fig. 1 to 4, this coil 24 is completely surrounded by a flexible plastic coating 34, except for one recess 26 or 28 in each end face. The coating 34 thus has a jacket 36 surrounding the coil 24 and end plates 30, 32 enveloping the coil at the end. The coating 34 sits firmly on the coil 24.

The trigger 22.2 shown in Fig. 5 also has an internal coil 24, on which a plastic coating 34.2, which corresponds in material and function to the coating 34, sits firmly. This coating 34.2 also has a jacket 36.2, which envelops the coil 24 in the areas parallel to its longitudinal axis 40.

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The coating 34.2 has several recesses 42 through which the solution 20 surrounding the trigger 22.2 can penetrate into the interior of the coil 24, through the coating 34.2, or come into contact with the surface of the coil. These recesses 42 consist of holes distributed around the circumference of the coating 34.2. These holes are so small that touching the trigger 22.2 does not allow contact with the coil 24 from the outside to the inside through the coating 34.2. The coil 24 is thus sufficiently enveloped on the outside by the coating 34.2 on the one hand, and on the other hand the solution 20 can pass through the casing 36.2 into the interior enclosed by the coating 34.2 and thus into the area of the coil 24.

The coil 24 of the triggers 22, 22.2 is sufficiently protected inside the cover 34, 34.2 so that direct contact between the coil and the casing of the heat pad can be ruled out. The cover 34, 34.2 prevents the coil 24 from bending so much by simply hitting the trigger 22 or 22.2 that crystallization and thus the exothermic process of the solution 2 0 is triggered.

Claims (5)

1. Heat pad filled with 1. a supercooled aqueous sodium acetate solution ( 20 ), 2. an elastically deformable housing ( 34 ) within said aqueous solution ( 20 ), 3. a metallic body ( 24 ) within the housing ( 34 ) which is mounted in the housing ( 34 ) in such a way that this metallic body ( 24 ) undergoes such elastic deformation when the housing ( 34 ) is elastically deformed that crystallization of the solution ( 20 ) can be triggered in an exothermic process, characterized in that 4. the metallic body consists of a single helical coil ( 24 ), 5. the housing is a plastic cover ( 34 , 34.2 ), 6. the plastic coating ( 34 , 34.2 ) is firmly attached to the coil ( 24 ), 7. at least one recess ( 26 , 28 , 42 ) is present in the plastic coating ( 34 , 34.2 ) so that the solution ( 20 ) can reach the area of the coil ( 24 ). 2. Heat pad according to claim 1, characterized in that 1. the covering ( 34 , 34.2 ) surrounds the coil ( 24 ) like a tube. 3. Heat pad according to claim 2, characterized in that 1. the coating ( 34 , 34.2 ) projects beyond the free end of the helix ( 24 ) in the direction of the longitudinal axis ( 40 ) of the helix ( 24 ). 4. Heat pad according to claim 2, characterized in that 1. the covering ( 34 , 34.2 ) surrounds the free end of the helix ( 24 ). 5. Heat pad according to one of the preceding claims, characterized in that 1. the plastic coating ( 34 ) is an injection-molded part.