EP1619930B1 - Linear reflector and radiant heater assembly and heating assembly comprising the same - Google Patents

Abstract

The linear radiant heater (1) has a glass tube (10) containing an electrical resistance heating spiral (30) with electrical connectors (40) and a reflective metallic coating (20) over the upper half of the length acting as a reflector and glass tube heater with electrical terminals (50,52).

Description

The invention relates to a linear reflector radiant heater according to the preamble of claim 1 and a heating arrangement with the same according to the preamble of claim 14.

For the direct surface heating of solids and liquids are used in the food industry, eg. B. for heating molds for chocolate, linear radiant heaters used, which consist of a tubular, internally heated glass body and are equipped with a radiation reflector surrounding a partial surface of the tubular glass body. In this way, energy-saving direct heating of a selected surface area is possible. For this purpose, usually straight elongated cylindrical glass tubes an inner helical resistance heating element is used, wherein the radiation reflector is provided on the chocolate liquid surface opposite side of the glass tube.

In many technical applications of the aforementioned type, in particular in the food industry, particularly strict purity conditions apply. It has therefore long been sought ways, as in the case of a defect of the radiant heater, in particular a glass break can be avoided that contaminating or hazardous substances from the radiant heater on the directly heated liquid or solid surface and thus spoil the liquid or the solid can. It has been found that mechanical means such as z. B. in automotive windows to avoid the risk of splintering are known to provide sufficient security. In addition, sufficient infrared transmission is required. In the case of the line-shaped radiant heaters in question, the surface temperatures of the heated glass body are extraordinarily high on the one hand, and, on the other hand, the heat radiation load per unit area is comparatively high because of the tubular design of the heated glass body high. The temperature load of the glass body is also due to the presence of the radiation reflector on approximately one half of the circumference of the linear glass body unbalanced.

Out US 2003/175020 A1 a line-shaped radiant heater for direct surface heating of liquids or solids is known, which has a tubular, internally heatable glass body and a radiation reflector. The radiation reflector surrounds a partial surface of the tubular radiation body and is formed of electrically conductive material. The radiation reflector is covered by a protective layer and laterally surrounded. The protective layer is made of electrically non-conductive material, so that the radiation reflector is electrically insulated on one side by the glass body and on the other side by the protective layer. Linear radiant heaters of comparable construction are made GB-A-1541980 such as DE 10253582 B3 known. Out DE 20314653 U1 such as DE 20314654 U1 In each case, line-shaped radiant heaters are known, in which heat-radiating films form a heat source, which is surrounded by a housing made of metal or the like.

Based on this, the present invention seeks to reduce the risk of contamination of directly heated goods by generic radiant heaters. This object is achieved by a linear reflector radiant heater having the features of claim 1 and a heating arrangement with the features of claim 14.

The invention is based on the recognition that in the line-shaped radiant heaters in question a thermal overload can occur at any point along the longitudinal extent of the internally heated glass body and does not necessarily have to spread from there. Under certain circumstances, the integrity of the internally heated glass body remains long after the occurrence of local overheating, even if at a certain point along the longitudinal extent of the internally heated glass body cracks have already formed in the glass. Usually will cause such local overheating that there burns the normally used electrical resistance heating coil, so that the damage is then detected and the radiant heater can be replaced before the glass body loses its integrity. It has now been found that, among other things, an early detection of damage to the line-shaped radiant heater is possible by the invention in such a way that the heating can be switched off in good time before broken glass, harmful vapors or other contaminants can reach the directly heated liquid or solid surface , The invention also makes it possible to detect a vitreous fracture in the non-heating state. The invention makes use, on the one hand, of the knowledge that an electrical interconnect extending along the longitudinal extent of the tubular glass body permits a sufficiently reliable early detection of damage to the tubular glass body, although the interconnect does not cover the circumference of the tubular glass body, but only a strip-shaped surface area, extending from one end to the other of the tubular one heated glass body extends. On the other hand, the invention makes use of the knowledge that the electrical conductor can be formed as a tearable layer, so that even relatively low longitudinal stresses in the tubular glass body lead to at least partial tearing of the layer and thus interrupting the conductor or changing their line characteristic. Although it is in the electrical safety technology, including from the DE 7142597 U long known to use the galvanic interruption of a conductor for switching off a heating current. However, these known methods can not be transferred to linear reflector radiators and their particular use for the direct heating of liquids and solids, because the geometric conditions and application problems are extremely different.

It is achieved by the invention that, with linear reflector radiant heaters, damage to the tubular heated glass body is detected at such an early stage and contamination of the directly heated surfaces of liquids or solid substances, in particular in the food industry, can be virtually completely avoided.

As a tearable layer, vapor-deposited electrically conductive layers have proven to be particularly effective.

In principle, the radiation reflector can be arranged at a distance from the glass body. As a particularly efficient arrangement, the use of a directly attached to the tubular glass body reflector layer has been found, especially if it also serves as a tearable layer in the context of the invention. If such a reflector layer is formed as a meandering path, a particularly high cut-off reliability is achieved at the same time good reflection performance. A rupturable layer according to the invention may also be provided, if appropriate, exclusively on the side opposite the reflector (front side) of the glass body, if the transmission reduction thereby becomes acceptable in the individual case Keeps borders. Especially preferred is a combination of a rupturable layer serving as a reflector with at least one rupturable layer on the front side of the glass body.

If the line-shaped radiant heater is equipped according to an embodiment of the invention with a measuring and switching device which detects changes in the line characteristic associated with damage to the heatable layer, thereby an early detection of damage to the tubular glass body can be achieved even if the tearable Layer not yet galvanically severed but only torn. Such a measuring device may also be integrated in the line-shaped radiant heater, while a switching device, for. B. for controlling or switching off the heating or for the output of optical / or acoustic alarm from the linear radiant heater is usually separated.

A "linear radiant heater" in the sense of this invention may be any of such radiant heaters consisting of a "tubular" glass body, e.g. bent, cast, or otherwise machined into arbitrary shaped shapes (e.g., meandering, circular, helical, etc.), not just straight elongated tubular bodies. In this case, the cavity cross section of the tubular glass body is not necessarily circular, but can be chosen arbitrarily (for example, square, elliptical, etc.). The outer contour of the glass body can therefore also be of a planar nature, such as e.g. in the Mehrrohrheizstrahlern described below or similar to so-called multi-wall sheets.

Mehrrohrheizstrahler have proven to be particularly effective, which are not only very effective as twin pipes with common radiation reflector not only very effective, but are very safe to operate within the meaning of the object of the invention.

The above-mentioned and the claimed components to be used according to the invention described in the exemplary embodiments are not subject to special conditions of size, shape, material selection and technical design, so that the selection criteria known in the field of application can be used without restriction.

Fig. 1

einen Einzelrohr-Strahler mit gleichzeitig als Reflektorschicht dienender reißbarer Schicht in Querschnittsansicht;

Fig. 2

einen Zwillingsrohr-Strahler mit gleichzeitig als Reflektorschicht dienender reißbarer Schicht in Querschnittsansicht (Schnitt entlang der Linie II - II gemäß Fig. 3a);

Fig. 3

denselben Zwillingsrohr-Strahler in Draufsicht (Ansicht A gemäß Fig. 2 und 5);

Fig. 3a

von der Darstellung nach Fig. 3 eine Detailansicht;

Fig. 4

denselben Zwillingsrohr-Strahler in Draufsicht von unten (Ansicht B gemäß Fig. 2 und 5);

Fig. 5

denselben Heizstrahler in Seitenansicht (Ansicht C gemäß Fig. 2, 3 und 4), sowie

Fig. 6

eine weitere Alternative eines linienförmigen Heizstrahlers in Draufsicht von unten;

Fig. 7

denselben linienförmigen Heizstrahler in Seitenansicht.

Aus Figur 1 ist ein erfindungsgemäßer Heizstrahler 1 im Querschnitt ersichtlich, der im wesentlichen aus einem Glasrohr 10, einer in die Oberfläche des Glasrohres 10 eingearbeiteten, insbesondere aufgedampften, reißbaren Schicht 20 und einer im wesentlichen zentral angeordneten Wendel 30 eines elektrischen Heizwiderstandes besteht. Die reißbare Schicht 20 ist dabei derart in das Glasrohr 10 eingearbeitet, dass sie deren einen (in der Zeichnung oberen) Teil bedeckt und damit gleichzeitig als Reflektorschicht dient, so dass der Großteil der von der Wendel 30 erzeugten Wärmestrahlung (Infrarotstrahlung) nach "unten" aus dem Glasrohr 10 austritt. Die Position, die Gestalt und die Breite der als Reflektorschicht dienenden reißbaren Schicht 20 ist im allgemeinen jedoch völlig frei wählbar. Vorzugsweise besteht die reißbare Schicht 20 aus einem Metall, insbesondere aus Gold.Further details, features and advantages of the subject matter of the invention will become apparent from the dependent claims, as well as from the following description of the accompanying drawings, in which - exemplary embodiments of a linear reflector Heizstrahlers invention are shown. In the drawings shows:

Fig. 1

a single-tube radiator with simultaneously serving as a reflector layer rupturable layer in cross-sectional view;

Fig. 2

a twin tube emitter with simultaneously serving as a reflector layer tearable layer in cross-sectional view (section along the line II - II according to Fig. 3a );

Fig. 3

the same twin tube radiator in plan view (view A according to Fig. 2 and 5 );

Fig. 3a

from the presentation Fig. 3 a detail view;

Fig. 4

the same twin tube radiator in plan view from below (View B according to Fig. 2 and 5 );

Fig. 5

the same radiant heater in side view (view C according to Fig. 2 . 3 and 4 ), such as

Fig. 6

a further alternative of a linear radiant heater in plan view from below;

Fig. 7

the same line-shaped radiant heater in side view.

Out FIG. 1 is an inventive radiant heater 1 in cross-section apparent, which consists essentially of a glass tube 10, an incorporated into the surface of the glass tube 10, in particular vapor-deposited, rupturable layer 20 and a substantially centrally disposed coil 30 of an electrical heating resistor. The tearable layer 20 is incorporated into the glass tube 10 in such a way that it covers one of its parts (upper part in the drawing) and thus at the same time serves as a reflector layer, so that the majority of the heat radiation (infrared radiation) generated by the helix 30 is "downwards". exits the glass tube 10. However, the position, the shape and the width of the rupturable layer 20 serving as a reflector layer can generally be chosen freely. Preferably, the tearable layer 20 is made of a metal, in particular gold.

FIG. 2 shows a second embodiment, a radiant heater 1 in which the glass tube 10 is configured such that it provides two mutually parallel, mutually separate cavities, each centrally a helix 30 is arranged in the longitudinal direction of the glass tube 10. The incorporated into the glass tube 10 and serving as a reflector layer rupturable layer 20 substantially covers the one (upper in the drawing) half of the glass tube 10, so that the heat generated by the two coil 30 turn for the most part from the (lower in the drawing ) Area of Glasrohres10 emerges. However, it will be apparent to those skilled in the art that more than one tearable layer is used or that a tearable layer can be multi-part.

FIG. 3 shows the twin-tube radiant heater 1 with serving simultaneously as a reflector layer tearable layer 20 in plan view (in the drawing from above). At the ends of the radiant heater 1 are provided connections 40, with which the not visible in the present figure coil 30 can be supplied with electric current. Preferably, the terminals 40 correspond to conventional terminals, so that a simple replacement or installation of the radiant heater 1 according to the invention in existing holding devices is unproblematic. In the left and right end of the radiant heater 1 contacts (not shown in the drawing) are arranged, which are in electrically conductive connection with the rupturable layer 20 serving as a reflector layer. The contacts are each secured to the glass tube 10 or to the surface thereof by means of a holder 52, which at least partially surrounds the glass tube 10, in order thus to ensure a sufficient hold and reliable connection of the contacts. The contacts may either be completely outside with a rupturable layer 20 disposed on the outside of the glass tube 10, or may lead outwardly at a rupturable layer 20 disposed in the glass tube 10 or on the inside of the glass tube 10. An external measuring and switching device (not shown), which can detect a change in the line characteristic of the at least one rupturable layer 20, can be connected to these contacts.

FIG. 3a is an enlarged detail of the in FIG. 3 shown enlarged left and in the holder 52 and with the tearable layer 20 in electrical connection terminal contacts 50. Furthermore, it is easy to see how the reflector layer results from a one-piece, meandering and rupturable layer. In this case, the distance a between two loops in the longitudinal direction is kept low, so that a reflector layer which is as dense as possible is obtained, and accordingly little heating power (infrared radiation) is transmitted. On the other hand, however, the distance a must be at least so great that an unavoidable expansion of the tearable layer 20 during operation, especially in the longitudinal direction of the radiant heater 1, leads to an unwanted additional connection of the loops, which improves the accuracy and reliability of the tearable layer 20 as a breakage sensor would reduce.

FIG. 4 shows the twin-tube radiant heater 1 according to the invention in plan view from below. In addition to the already explained terminals 40, the mutually parallel helix 30 can be seen in this illustration. At the left and right end portion of the glass tube 10 at least partially comprehensive brackets 52 for the contacts 50, not shown, which are in electrical contact with the tearable layer 20, also not shown, can be seen.

FIG. 5 finally shows the radiant heater 1 according to the invention in plan view from the side. In addition to the rupturable layer 20 serving as a reflector layer, which is arranged on the upper side of the glass tube 10, both the helix 30, the terminals 40 and the holders 52, to which the terminal contacts 50 are fastened, can be seen. At the terminal contacts 50, for example, an external measuring and switching device can be connected, which checks the line characteristic of serving as a reflector layer rupturable layer 20 and a breakage of the glass tube 10 and an associated damage to the tearable layer 20 generates a corresponding signal, which can be used to regulate the power supply to the terminals 40, in particular to turn off, or to issue an audible and / or visual alarm signal, so that a threat to the environment can be almost excluded.

FIG. 6 shows a further alternative of the line-shaped radiant heater 1 according to the invention in plan view from below. In addition to the mutually parallel helix 30 extending conductors are visible in this alternative at the bottom, which are sections of the tearable layer 20. These run transversely to the longitudinal direction of the linear heater 1 and "monitor" in the given case, in particular its underside. Therefore, the distance between these sections is relatively large, so that the exiting infrared radiation is reduced only slightly. The portions of the tearable layer 20 may be connected to a rupturable layer extending in the longitudinal direction of the radiant heater 1 such that the entire rupturable Layer 20 extends on one path from the one side of the radiant heater 1 to the other side.

Such a single-path arrangement is in FIG. 7 more clearly, which shows the alternative in connection with a serving as a reflector meandering rupturable layer. As can be seen, the meandering tearable layer does not form a loop at four points, but rather circles around the circumference slightly helically (with a slight longitudinal displacement by the distance a) of the radiant heater 1, and again on the other side with another Part of the meandering layer to connect, so that the adjacent meandering sections are connected by the sections. As a consequence, if the tearable layer 20 is to be interrupted or weakened at any location (within a meandering area or portion), the tearable layer 20 will no longer provide a conductive connection between the terminal contacts 50, or itself their line characteristics, eg their electrical resistance, changes.

It goes without saying that the number of such sections surrounding the radiant heater 1 is not limited to four. Rather, it is conceivable that the at least one tearable layer is arranged as extending in the longitudinal direction, wherein the number of sections and their arrangement can be arbitrarily designed, so that a single-path "net-like" structure is conceivable.

LIST OF REFERENCE NUMBERS

1

heater

10

glass tube

20

tearable layer

30

spiral

40

electrical connections

50

Connection contacts

52

brackets

a

Distance between two loops

Claims (14)

1. Linear heat radiator for direct surface heating of liquids or solids, as used in the food industry, comprising a tubular, internally heated glass body and a radiation reflector which surrounds part of a surface of the tubular radiant body, characterised in that at least one electrical conductor track extends as a tearable layer (20) along the longitudinal extent of the tubular glass body and the tearable layer (20) is connected at its end regions to outwardly lying or outwardly leading connector contacts (50).
2. Linear heat radiator according to claim 1, characterised in that the tearable layer (20) is a layer vapour-deposited onto the glass body surface.
3. Linear heat radiator according to claim 1 or 2, characterised in that the tearable layer (20) is configured with a meandering form.
4. Linear heat radiator according to one of the claims 1 to 3, characterised in that the tearable layer (20) comprises a heat-resistant and highly reflective material, in particular made from metal, preferably gold.
5. Linear heat radiator according to one of the claims 1 to 4, characterised in that the tearable layer (20) simultaneously serves as a radiation reflector.
6. Linear heat radiator according to one of the claims 1 to 5, characterised in that at least one tearable layer is arranged on the front side of the glass body opposing the radiation reflector.
7. Linear heat radiator according to claim 6, characterised in that the at least one tearable layer provided on the front side extends transversely to the longitudinal extent of the tubular radiant body.
8. Linear heat radiator according to claim 6 or 7, characterised in that the at least one tearable layer is conductively connected on the front side to the radiation reflector.
9. Linear heat radiator according to one of the claims 1 to 8, characterised in that a measuring and switching device which detects a change in the conduction characteristics associated with damage to the tearable layer (20) is provided.
10. Linear heat radiator according to claim 9, characterised in that the measuring and switching device is configured such that, in the event of a substantial change in the conduction characteristics of the tearable layer (20), a signal for regulating, in particular switching off, the heating and/or for an optical and/or acoustic alarm can be emitted.
11. Linear heat radiator according to claim 9 or 10, characterised in that at least the measuring device is integrated on or in the heat radiator (1).
12. Linear heat radiator according to one of the claims 1 to 11, characterised in that the heating is carried out by means of a resistive heating element extending substantially in the longitudinal extent of the tubular glass body, in the interior of the tube thereof.
13. Linear heat radiator according to one of the claims 1 to 12, characterised in that the heat radiator (1) is configured as a multi-tube heat radiator, preferably as a twin-tube heat radiator.
14. Heating arrangement for direct heating of surfaces of liquids or solids, particularly in the food industry, characterised by a linear heat radiator according to one of the claims 1 to 13.

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