GB2394634A

GB2394634A - a flexible heating element with insulated connection to power supply circuit

Info

Publication number: GB2394634A
Application number: GB0321388A
Authority: GB
Inventors: Ernst Merk
Original assignee: Beurer GmbH and Co
Current assignee: Beurer GmbH and Co
Priority date: 2002-09-19
Filing date: 2003-09-12
Publication date: 2004-04-28
Also published as: DE10243448B4; GB0321388D0; DE10243448A1

Abstract

The invention relates to a flexible heating element 1, such as a heating blanket, heating cushion or heating under-blanket, having a heating cord 2, laid in the heating element 1, said heating cord 2 being connected via a heating cord portion 2.1, which is led out of the heating element 1, and via an electrical wiring part 3, to an electrical supply 5. Improved user friendliness is achieved in that the led-out heating cord portion 2.1 is provided with a heat-insulating, flexible coating 4, which is applied on the outer insulation of the heating cord 2. The other end of the heating cord 2, with its at least two heating wires which are embedded in insulation, are connected directly 2.2, or indirectly 2.3 via an electrical component arrangement.

Description

FLEXIBLE HEATING ELEMENT

The invention relates to a flexible heating element, such as a heating blanket, heating cushion or heating underblanket, having a heating cord laid in the heating element, said heating cord being connected via a heating cord portion, which is led out of the heating element, via an electrical wiring part to an electrical supply line and terminating in the heating element with its other end by connection of its at least two heating wires which are embedded in insulation, said connection being produced directly or indirectly via an electrical component arrangement.

A flexible heating element of this type is indicated in DE 101 26 031 C1. In this known heating element, it is provided inter alla that the heating cords laid in the heating element, for example a heating blanket, is led out of the heating element at its one end region with a heating cord portion and is connected by the latter for example to a portion of a plugin coupling unit on the heating element side. The led-out heating cord portion has the advantage that the relatively flexible heating cord offers a flexible and readily accessible connection portion also outwith the blanket and does not interfere much during use. However, the heat arising in the heating cord portion can be undesirable so that frequently a heating cord portion of this type which is led out of the heating element is not required.

The object underlying the invention is to provide a flexible heating element of the initially mentioned type which is more user friendly.

This object is achieved with the features of claim 1. It is provided accordingly that the led-out heating cord portion is provided with a heatinsulating, flexible coating, which is applied on the outer insulation of the heating cord.

! This embodiment of the led-out heating cord portion with the coating configured in the mentioned manner prevents undesirable temperatures on

the outside of the led-out heating cord portion, the favourable connection possibilities being maintained.

Advantageous embodiment possibilities thereby reside in the fact that the coating is configured as a tubular casing, which is pushed-on or applied circumferentially by means of an elongated slot, or by extrusion or foaming.

The elongated slot can thereby be configured for example by means of a zip-

like configuration which can no longer be opened after its closure.

If it is provided that cavities are formed in the coating by means of webs or pores, then the heat insulation is provided by the air inclusions. A high flexibility is thereby obtained by corresponding choice of material; high electrical insulation properties not requiring to be taken into account since the latter are already ensured by the external insulation of the led-out heating cord portion.

A uniform integration of the coating with the advantage of being able to improve the connection points resides in the fact that the coating, in its transition region towards the heating element and/or in its further transition region towards the wiring part or the supply line, is provided with a connecting structure. Advantageous embodiment possibilities reside hereby in the fact that the connecting structure is produced by means of casting, welding, thermal embossing, gluing, interweaving, sewing, riveting or clamping.

The connection possibilities of the led-out cord portion are furthermore favoured in that the connecting structure has a kink protection part and/or strain relief part which is moulded onto the coating.

An unequivocal, protected connection to the wiring part is furthermore favoured in that the connecting structure associated with the wiring part has a cable socket which is moulded onto the coating.

The measures that the coating is provided with a thread structure as strain relief, which is connected, on the one hand, to the heating element and, on the other hand, to the wiring part or to the supply line, contributes further to the additional stabilization of the led-out heating cord portion.

The invention is subsequently explained in more detail by means of an embodiment with reference to the drawings, which show: Fig. 1 a schematic illustration of a heating element connected to an electrical wiring via a heating cord portion, Fig. 2 a first embodiment of a casing of a heating cord portion which is led out of the heating element, Fig. 3 and 4 further embodiments of casings of the heating cord portion which is led out of the heating element.

As is evident in Fig. 1, a heating cord 2 embedded in a flexible heating element 1 is disposed with its one end in the heating element 1, whilst its other end portion is led out of the heating element 1 and is connected to an electrical wiring part, which for its part is connectable via a supply line 5 to a supply voltage. The flexible heating element 1 concerns for example a heating blanket, a heating cushion, a heating underblanket or a cover, for example the heating cushion being able to be covered in a normal manner with a thermoplastic film.

As is likewise known per se, the heating cord 2 comprises at least two mutually insulated heating wires, which are disposed for example coaxially

relative to each other, the one heating wire being configured centrally and the other as a wound conductor which is spaced therefrom by means of insulation and the current being guided through the inner conductor in the opposite direction to the current in the outer conductor. In the present case, the two heating wires are connected to each other at the end disposed in the heating element either directly 2.2 or via an electrical circuit arrangement, for example the illustrated diode 2.3. The led-out heating cord portion 2.1 is connected at its free end to the electrical wiring part 3. The electrical wiring part 3, as is known per se, has a display 3.3, a switch part 3.2 with a first and a second switch 3.4, 3.4' and also a supply diode 3.5 delimiting the current supply in one switch position, the wiring part 3 being connected via line portions 3.1 to the heating wires at the free end of the led-out heating cord portion 2.1.

The led-out heating cord portion 2.1 which is configured very flexibly corresponding to the heating cord 2, is provided with a heat-insulating coating 4 which is configured for example as a closed casing, as is illustrated in more detail in Figs. 2 to 4. The casing 4 can thereby be configured as a tubular element or as a spray-painted coating. The heatinsulating coating 4 is furthermore configured very flexibly around the led-out heating cord portion 2.1 in order in practice not to restrict the flexibility of this heating cord portion 2.1. The heat insulation of the coating is achieved on the one hand by corresponding choice of material and on the other hand by the configuration of the casing, which has for example cavities 4.8 formed for example by webs 4.7 (cf. Fig. 4) or by means of pores. In the embodiment according to Fig. 4, an inner sleeve 4. 6 surrounding the outer insulation of the led-out heating cord portion 2. 1 and an outwardly spaced outer sleeve 4.5 are thereby separated from each other by means of the longitudinally extending webs 4.7.

The pores can be produced for example by extrusion or foaming of the ledout heating cord portion 2.1 directly on its outer insulation with suitable plastic material, a smooth or even a rough surface being able to be achieved. By extrusion or foaming there is no need to push on or apply the casing circumferentially, as in the case of a tubular embodiment. It is possible to

apply the tubular casing 4 circumferentially if the latter has an elongated slot, the elongated slot being able to be configured in the manner of a zip fastener which can no longer be opened after application. The heat insulation property of the casing can be chosen dependent upon the power of the heating cord, even a PVC tube being able to operate in particular at low power of e.g. 1 to 2 W/m whilst, at higher power, which can be for example on a short term basis up to 50 W/m at peak outputs (typically e.g. approximately 10 W/m), correspondingly higher heat insulation values are chosen.

Furthermore, as Figs. 2 and 3 show, a strain relief, for example in the form of embedded carrier threads 4.3 or a textile 4.4, can be integrated into the casing 4. As a result, the led-out heating cord portion 2.1 is mechanically protected in addition from tensile stress. For example, the casing 4 can be reinforced in the form of a tube by normal types of textile in order to achieve higher tensile strengths or dimensional stability; torsional reinforcement also being able to be achieved. The thread angle can be for example between 30 and 60 . By pushing on the textile tube, the diameter can be enlarged, or reduced by stretching (drawing); an additional plastic cover being able to be dispensed with in the case of a dense textile. Very fine and dense textile tubes are produced in so-called 1 K yarn (67 sex), loose to thicker types in 3K yarn (200 tex) and loose and coarse types in 6K yarn (400 sex). A sheer type of textile can also be used with a silicon and glass fabric insert of 70 /60 Shore A or the like. Hybrid textiles made of carbon/aramide 180 g/m2 with coloured aramide threads are also usable; various colour compositions being able to be chosen.

As Fig. 1 further shows, stabilising connecting structures are present in the transition region 4.1 between the led-out heating cord portion 2.1 and the heating element and also in the further transition region 4.2 between the free end of the led-out heating cord portion 2.1 and the wiring part 3 or the supply line 5, with which connecting structures a mechanically and/or optically improved transition is achieved. The transition regions 4.1, 4.2 can be

configured as strain relief and/or cable socket with protection against rotating and be produced for example by injection moulding or during extrusion. A connection to the strain relief integrated in the casing 4 is thereby also possible. The connection in particular to the flexible heating element 1 can be effected in various ways, such as for example by sewing, welding, gluing, riveting, casting or by placing weld points for example in large-scale implementation or by thermal embossing. In the case of heating cushions with a thermoplastic covering, in which the heating cords 2 or a led-out heating cord portion 2.1 is produced usually likewise from thermoplastic material, both parts can be connected relatively easily, for example by means of HE welding, ultrasound welding, gluing, riveting or thermal embossing. A kink protector is also achieved by the thus configured transition regions 4.1, 4.2. The connection can be effected on the heating element side for example also with padding material, such as foam, coated foam or non-woven material.

The requirement for adequate reversed bending strength is ensured by a suitable choice of material, such as e.g. plasticised PVC.

When producing the casing 4 by extrusion, a plastic material thread, e.g. made of polyester or the like or a plastic material strand or preinjected moulded part, can be inserted for example over the entire length and likewise be extruded with e.g. plasticised PVC for the purposes of strain relief. Other insulating materials made of thermoplastic plastic materials, such as e.g. thermoplastic elastomers, are also usable for the production of the casing 4.

A combination of different materials, e.g. with different heat conduction and strength, is also conceivable.

Claims

1. Flexible heating element, such as a heating blanket, heating cushion or heating underblanket, having a heating cord (2) laid in the heating element (1), said heating cord being connected via a heating cord portion (

2.1), which is led out of the heating element (1), and via an electrical wiring part (3) to an electrical supply line (5) and terminating in the heating element (1) with its other end by connection of its at least two heating wires which are embedded in insulation, said connection being produced directly or indirectly (2.2) via an electrical component arrangement (2.3), characterized in that: the led-out heating cord portion (2.1) is provided with a heat-insulating, flexible coating (4), which is applied on the outer insulation of the heating cord (2) 2. Heating element according to claim 1, characterized in that: the coating (4) is configured as a tubular casing, which is pushed-on or applied circumferentially by means of an elongated slot, or by extrusion or foaming.

3. Heating element according to claims 1 or 2, characterized in that: cavities (

4.8) are formed in the coating (4) by means of webs (4.7) or pores. 4. Heating element according to any one of the preceding claims, characterized in that: the coating (4), in its transition region (4.1) towards the heating element (1) and/or in its further transition region (4.2) towards the wiring part (3) or the supply line (5), is provided with a connecting structure.

5. Heating element according claim 4, characterized in that: the connecting structure is produced by means of casting, welding, thermal embossing, gluing, interweaving, sewing, riveting or clamping.

6. Heating element according to claims 4 or 5, characterized in that: the connecting structure has a kink protection part and/or strain relief part which is moulded onto the coating (4).

7. Heating element according to one of claims 4 to 6, characterized in that: the connecting structure associated with the wiring part (3) has a cable socket which is moulded onto the coating (4).

8. Heating element according to one of the preceding claims, characterized in that: the coating (4) is provided with a thread structure (4.3, 4.4) as strain relief, which is connected, on the one hand, to the heating body (1) and, on the other hand, to the wiring part (3) or to the supply line (5).