EP2318756B1 - Electrical circuit arrangement - Google Patents

Abstract

The present invention relates to an electrical circuit arrangement, in particular an electrical signal circuit arrangement and preferably a signal lamp which is used in hazardous areas. The circuit arrangement is equipped with at least one electrical component (1) which is arranged on a printed circuit board (2) produced from a heat-conducting material. The electrical component (1) is, in particular, a luminous means (1). A cooling device (6, 7) which is in thermal contact with the printed circuit board (2) is also realized. According to the invention, the cooling device (6, 7) is in at least two parts, with a heat sink (7) and at least one heat pipe (6). In this case, the heat pipe (6) thermally connects the printed circuit board (2) to the heat sink (7).

Description

The invention relates to an electrical circuit arrangement, in particular electrical signal circuit arrangement, preferably signal light, for use in explosive areas, with a housing made of plastic, further comprising at least one on a manufactured of a thermally conductive material printed circuit board arranged electrical component, in particular light source, and a cooling device in thermal contact with the printed circuit board, wherein the cooling device is formed at least in two parts with a heat sink and at least one heat pipe, and wherein the heat pipe thermally connects the printed circuit board with the heat sink. - The addressed and arranged on the circuit board bulbs are usually one or more LEDs.

Signal lights are commonly used to generate one or more optical signals that serve to indicate any hazards, peculiarities, etc. For example, signal lights are used for reporting and warning, for example with regard to faults on machines. Signal lights but also escape routes can show as well or under certain circumstances indicate advertising space. The same applies to acoustic signaling devices, which are also to be qualified as electrical signal circuitry in the above sense.

As soon as bulbs are mounted on the existing of a thermally conductive material circuit board in the example, there is the problem of heat dissipation in the context of special applications. This already applies to electrical circuit arrangements in general and to signal lights in particular, which are used in potentially explosive areas, that is to say so-called explosion-proof electrical (signal) circuit arrangements respectively signal lights or signal loudspeakers. Because such signal lights have either a flameproof enclosure of the housing, so that the removal of heat generated in the housing is a problem. Or the housings are completely or predominantly filled with a potting compound, so that settle comparable problems, since such potting compound usually has only an extremely poor thermal conductivity.

The aforementioned problem therefore generally applies to all housing of signal lights, because due to the usually required high light intensity of the bulbs must often be expected with an increased amount of heat loss. This heat loss can lead to an increased temperature in the interior of the housing relative to the ambient temperature. The increased temperature inside the housing makes the use of the signal light in the example case in potentially explosive areas problematic. Because there is a risk that partial areas of the housing heat up significantly higher than other areas. As a result, so-called "hot spots" are observed on the surface of the device, which can be sources of ignition for the surrounding atmosphere in potentially explosive atmospheres.

This applies not only to certain gas mixtures or the occurrence of flammable gases, but also to, for example, combustible dusts during the processing of powders. In this context, it should be additionally considered that the smaller the given distance between the associated heat source and the surface, the higher the partial heating by radiation and convection. That is, the occurrence of the described "HotSpots" is favored by a small distance between the heat source and the surface and an insufficient heat dissipation of the surface.

For this reason, one has in the prior art after GB 2 428 467 A already implemented an expansive heat sink in an explosion-proof signal light. The heat sink or cooling block is connected to the ambient atmosphere. On the heat sink or cooling block is the circuit board with LEDs arranged thereon. The circuit board itself is made of aluminum or other suitable material with high conductivity.

Due to the fact that, in the prior art, the printed circuit board with the LEDs located thereon is or must be arranged directly on the cooling block, the possible embodiments of the signal light are limited. In particular, this hardly barely cylindrical or towering signal lights can be realized, which are equipped with a slim long extended housing.

Similar embodiments are also in the generic state of the art according to the US 2008/0002410 A1 observed. Here, a signal light is realized, which is thermally connected via heat pipes with a heat sink placed outside of a housing. The heat sink is designed with cooling fins. Individual LEDs are supported by a separate support plate.

The invention is based on the technical problem to develop such electrical circuitry so that design limitations are no longer observed and a cost-effective embodiment is present with perfect heat dissipation.

To solve this technical problem, the invention proposes in a generic electrical circuit arrangement that the heat sink is placed in a housing recess and at the same time as a mounting flange for the circuit arrangement is formed in total. In the context of the invention, distances of a few centimeters or several tens of centimeters are usually bridged by the at least one heat pipe.

Thus, according to the invention, at least one heat pipe or a so-called "heat pipe" is used, which respectively thermally connects the printed circuit board with the electrical component arranged thereon to the heat sink. As a result, the heat sink acts as a heat sink and any heat loss of the electrical component is finally forwarded to the thermally conductive material made of printed circuit board and the heat pipe to the thermally conductive heat sink connected thereto and there usually distributed over a relatively large area to the ambient air. In the heat pipe used is a heat exchanger, which usually provides a high heat flux density available by using heat of vaporization of a heat transfer medium received in the heat pipe. In the heat transfer medium or working medium may be water, which is received in the interior of the mostly hermetically encapsulated heat pipes.

If there is now a heat input, for example in the region of the printed circuit board, then the heat transfer medium or working medium begins to evaporate. The resulting vapor flows in the direction of the heat sink or the heat sink, where it condenses because of its lower temperature. Here, the previously recorded heat (heat loss of the arranged on the circuit board electrical component) is released again. The now (again) liquid working medium usually returns by gravity or in the case of a heat pipe by capillary force back to the place of heat input or distributed in the interior of the heat pipe.

Within heatpipes or heat pipes, the liquid or, in general, the working medium is returned to the location of the heat input with the aid of the already mentioned capillaries. Consequently, the condensed working medium can flow back into the capillary independently of storage. In this way, heat pipes or heat pipes are able to work in weightlessness and in particular regardless of the installation position. In most cases, the capillaries are formed in a kind of wick inside the heat pipe, whereas the space surrounding the wick and / or inside is used for steam guidance.

Before the required working fluid is introduced into the heat pipe, it is usually necessary to mechanically evacuate the heat pipe. Since in the present case the temperature range between about 0 ° C and 100 ° C is primarily covered, water is suitable as a heat transfer medium or working medium. In addition, copper is usually used for the production of the heat pipe or the heat pipe, since this can be easily shaped and also has a high thermal conductivity. Such heat pipes or heatpipes are commercially available today in various lengths.

It has been proven that the heat sink ultimately representing heat sink is also designed as a mounting flange for the described electrical circuit arrangement as a whole. This provides a dual benefit as it were. For a housing receiving the electrical circuitry is usually made of plastic, is therefore hardly suitable for immediate attachment to a wall, a ceiling a housing, etc. Here, rather, the same time designed as a mounting flange heat sink is used, which provides the necessary provides mechanical stability for the mounting of the electrical circuitry.

All the more so, since the mounting flange or heat sink is equipped according to an advantageous embodiment with additional cooling fins, which at the same time increase its stability, but in any case increase the surface and thus enhance the heat transfer to the environment. In addition, the heat sink may be equipped with a cold source, which may be an example of a Peltier element. This additional source of cold is usually used when the heat dissipation through the heat sink or the heat sink in the application is not sufficient.

The printed circuit board made of a thermally conductive material is usually carried by a housing insert, in turn, with the already addressed housing is mechanically connected. For cost reasons, the housing is made in the present case of plastic and is usually filled with a potting compound to provide the required explosion-proof design available. In fact, among other things, the potting compound prevents exposed contacts from causing an ignitable mixture to explode or from sparking. The potting compound is, as usual, an insulating plastic, which is filled into the housing usually in the overhead position in the (tough) liquid state and then hardens.

You will usually work with different potting compounds. This can be attributed to the fact that the housing is regularly formed at least in two parts with an opaque base body and a transparent signal hood. As a consequence, the potting compound is regularly made transparent in the area of the signal hood, whereas otherwise a cloudy or opaque potting compound is used.

The signal hood and the main body are usually united together only by a plug connection. As soon as the potting compound is poured into the housing in the overhead position and cured, it ensures that the two housing parts (base body and signal hood) are captively coupled to one another. To further stability also contributes to the fact that the housing insert carrying the circuit board is regularly connected to the housing and of course then with the cured potting compound.

The invention is also a structural unit, which is composed of an electrical circuit arrangement of the type described and is additionally equipped with an adapter. This adapter ensures or ensures that via a common supply line and the adapter not only an electrical circuit, but for example, two or even more can be supplied. So it is conceivable to combine a signal light with a signal speaker or two signal lights each other respectively two signal speakers. That depends on the importance of the attention signal in the Wam area to be upgraded.

As a result, an electrical circuit arrangement and a structural unit of the electrical circuit arrangement and the adapter are made available, first of all by the almost unlimited design variety of the housing and in particular the arrangement of the lamp or of the printed circuit board carried by the electrical component and the associated cooling device distinguished. This is achieved by the invention in that the loss-heat-producing electrical component is connected to the heat sink via the printed circuit board carrying it and one or more heat pipes.

This heat sink is advantageously arranged in a housing recess, thus in thermal contact with the environment. This also applies and in particular for the case that the housing is made entirely or predominantly of plastic. Because the heat sink also represents the mounting flange for the circuit as a whole, a practical dual benefit is provided. In addition, if necessary, a base can be used as an additional heat sink to which the heat sink or mounting flange is fixed. For this base area or base may be a (metal) machine housing or the like. For an additional increase in surface area of the heat sink or mounting flange may provide additional cooling fins or an optional source of cold.

Overall, the described electrical circuit arrangement of the shape of the housing can be arbitrarily designed, especially since the housing is usually designed as a low-priced plastic injection molded part. Nevertheless, the required explosion-proof equipment is provided, which not only ensures the reliable dissipation of the resulting heat loss inside, but also the fact that the interior of the housing is filled with a potting compound. This potting compound also has a dual function. It not only ensures that electrical cables or the electrical component accommodated on the printed circuit board are hermetically sealed, but at the same time ensures that the two housing parts (main body and signal hood) are perfectly connected to each other, without additional fastening means at this point would be required. Here are the main benefits.

Fig. 1 und 2

zwei jeweilige Längsschnitte durch eine elektrische Schaltungsanordnung und

Fig. 3

eine Baueinheit aus einer abgewandelten elektrischen Schaltungsanordnung und einem zugehörigen Adapter.

In the following, the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment; show it

Fig. 1 and 2

two respective longitudinal sections through an electrical circuit arrangement and

Fig. 3

a structural unit of a modified electrical circuit arrangement and an associated adapter.

In the figures, an electrical circuit arrangement is shown, which is used for use in potentially explosive areas. The electrical circuit arrangement is a signal circuit arrangement, in the present case a signal light. For the basic structure of the circuit arrangement or signal light include one or more electrical components 1, which is in each case to LEDs 1. These components 1 and LED's 1 are received on a printed circuit board 2 made of a thermally conductive material. The circuit board 2 is made in the embodiment of a metal, in particular aluminum. The LEDs 1 are SMD LEDs 1.

On the basis of a comparative analysis of the Fig. 1 and 2 it can be seen that the LEDs or lamps 1 are arranged in a circle in comparison to a central axis A of a housing 3. Opposite this axis A, the housing 3 is rotationally symmetrical. In this way, the light emitted by the LEDs or light sources 1 is emitted in all spatial directions, so that an all-round light emission is ensured.

The respective printed circuit board 2 is supported by a housing insert 4, which in turn is mechanically connected to the housing 3. The housing insert 4 is composed of an insert foot 4a and an insert head 4b, wherein the insert head 4b is equipped in cross-section as a polygon with side surfaces 4c, which each carry a printed circuit board 2. For this purpose, the respective printed circuit board 2 is connected to the insert head 4b by means of or by resorting to a plurality of screws 5.

With the circuit board 2 is a cooling device 6, 7 in thermal contact, which is best in the sectional view of the Fig. 1 and 3 recognizes. According to the invention, this cooling device 6, 7 is composed of a heat pipe 6 and a heat sink 7. The heat pipe 6 thermally connects the respective printed circuit board 2 to the cooling body 7 arranged spatially remote therefrom. For this purpose, the heat pipe 6 is centrally accommodated in the operating head 4b of the housing insert 4 in the exemplary embodiment.

How to use the Fig. 1 and 3 recognizes the question insert head 4b is solid and made of metal (aluminum) and equipped with a hollow bore 8, which receives one end of the heat pipe 6 in its interior. About this hollow bore 8 takes place at the beginning already described heat input into the heat pipe 6. Also, the heat sink 7 is equipped with a hollow bore 9, wherein the hollow bore 9 in conjunction with the heat sink 7 is the previously described heat sink. Consequently flows from the LEDs 1 produced heat loss via the insert head 4b, the heat pipe 6 finally to the heat sink 7, which acts as a heat sink.

Because the heat pipe 6 is equipped as a copper pipe with enclosed inside an encapsulation heat transfer medium, in particular water, the heat pipe 6 can easily bend and easily adapt to the topological conditions in the interior of the housing 3. Any heat loss of the LEDs 1 is received via the associated circuit board 2, because the electrical component or the LED 1 is mounted in the example on the circuit board 2 with the interposition of a thermal paste or the like. From the circuit board 2, the heat is transmitted to the insert head 4b of the housing insert 4, which is also made of a thermally conductive material (metal). With the insert head 4b is one end of the heat pipe 6 in thermal contact.

In the interior of the heat pipe 6, the resulting heat loss is now converted into latent heat and transported to the heat sink in the form of the heat sink 7. Since the heat sink 7 is at the same time designed as a mounting flange 7 for the circuit arrangement or the housing 3 as a whole, the heat thus transported is distributed over a large area. This applies even more in the event that the heat sink 7 is equipped with supplementary and not explicitly shown cooling fins. Also, an additional source of cold in the form of a Peltier element can be used here, but this is also not shown.

It can be seen that the heat sink 7 is placed in a housing recess 10. As a result, the heat sink 7 is directly in thermal contact with the ambient atmosphere. This is of particular importance, as the housing 3 is made of plastic in the exemplary embodiment, thus has a poor thermal conductivity. In any case, the heat loss from the LED's 1 ultimately over that in the housing opening 10th placed heat sink 7 delivered to the ambient air respectively ambient atmosphere.

In the present case, the housing 3 is formed essentially in two parts and cylindrically with an opaque main body 3a and a transparent signal hood 3b. As a result of the transparent signal hood 3b, the light emitted by the LEDs 1 light can be radiated all around easily and provides the desired signal effect. To this end, the circumstance contributes to the fact that the housing 3 is filled with a potting compound 11a, 11b in the interior. This potting compound 11a, 11b is filled in the overhead position of the housing 3 and of course with mounted housing insert 4, mounted LED's 1 and also realized cooling device 6, 7 in viscous state. Previously, the opaque main body 3a and the transparent signal cap 3b have been coupled to each other via respective snap-in connections 12 or enter into a mutual plug connection. As soon as the potting compound 11a, 11b hardens, the transparent signal cap 3b and the base body 3a are captively coupled together.

The potting compound 11a is a transparent potting compound which fills the interior of the housing 3 in the region of the signal hood 3b. Below the filled with the aid of the transparent potting compound 11 a space is the cloudy or opaque further potting compound 11 b. Both potting compounds 11 a, 11 b are successively filled in the housing 3, first the transparent potting compound 11 a and then the opaque potting compound 11 b.

Finally, the Fig. 3 an assembly of the already described electrical circuitry respectively the signal light and an adapter 13. This adapter 13 is equipped with a flange 14, to which a further signal light or a signal speaker can be arranged. About the adapter 13 are both electrical Circuit arrangements supplied together with the required electrical energy. It can be seen that the two electrical circuit arrangements are arranged at right angles to each other in the embodiment, which of course is not a mandatory feature.

Claims (9)

1. An electrical circuit arrangement, in particular an electrical signal circuit arrangement, preferably a signal light, for deployment in regions hazarded by explosions, with

   - a housing (3) manufactured from plastic, furthermore with

   - at least one electrical component (1), in particular a lighting means (1), arranged on a circuit board (2) produced from a heat-conducting material, and with

   - a cooling unit (6, 7) located in thermal contact with the circuit board (2), wherein

   the cooling unit (6, 7) is designed in at least two parts with a cooling body (7) and at least one heat pipe (6), and wherein
   the heat pipe (6) connects the circuit board (2) thermally with the cooling body (7), characterised in that

   - the cooling body (7) is positioned in a housing recess (10), and

   - at the same time is designed as a whole as an attachment flange (7) for the circuit arrangement.
2. The electrical circuit arrangement in accordance with Claim 1, characterised in that the cooling body (7) is fitted with additional cooling ribs or a cold source, for example a Peltier element.
3. The electrical circuit arrangement in accordance with Claim 1 or 2, characterised in that the circuit board (2) is supported by a housing insert (4).
4. The electrical circuit arrangement in accordance with Claim 3, characterised in that the housing insert (4) is connected with a housing (3).
5. The electrical circuit arrangement in accordance with one of the Claims 1 to 4, characterised in that the interior of the housing (3) is filled with a potting compound (11 a, 11 b).
6. The electrical circuit arrangement in accordance with one of the Claims 1 to 5, characterised in that the housing (3) is designed in at least two parts with an opaque base body (3a) and a transparent signal cover (3b).
7. The electrical circuit arrangement in accordance with one of the Claims 1 to 6, characterised in that the potting compound (11 a, 11 b) is configured with variable transparency, and in the region of the signal cover (3b) is designed to be transparent and is otherwise unclear or non-transparent.
8. An assembly consisting of an electrical circuit arrangement in accordance with one of the Claims 1 to 7, and an adaptor (13).
9. The assembly in accordance with Claim 8, characterised in that the adaptor (13) has at least one connecting flange (14) for a further electrical circuit arrangement in accordance with one of the Claims 1 to 7.

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