DE102011008304B4 - Arrangement for detecting a Heizmittelbruches - Google Patents

Abstract

Arrangement for detecting a heating medium break, comprising -. a vacuum chamber (1) having an electrically conductive inner chamber wall (2); Figs; a heating means (4), which is held by passive heating means (5) in the vacuum chamber (1) electrically isolated at a distance from the chamber wall (2); Figs; a transformer (6) having a secondary coil (7) for the electrical supply of the heating means (4); Figs; a current-sensitive electrically connected switch (10) arranged between the chamber wall (2) and a tap (9) of the secondary coil (7) with at least one make contact (11) for interrupting the electrical supply of the heating means (4) in the event of a short circuit between the heating medium caused by fracture (4) and the chamber wall (2) and the resulting current flow through the switch (10).

Description

In the field of vacuum technology, the invention relates to an arrangement for detecting a defective heating means. Preferably, in a vacuum chamber arranged on the bottom side heating means such as heating rods from continuously electrically conductive material such as CFC in particular (carbon fiber reinforced carbon) into consideration.

CFC materials can be used at temperatures up to 3000 ° C in a vacuum. In addition to their suitability for thermal protection, they are also beneficial for heating purposes. The material in the form of a rod or strip heats up to several 100 ° C by a current flowing through it. The brittle material demands a compromise regarding the desired stability and heating capacity in the choice of the cross section. As a result of the operational aging of the material also decreases its stability. On the negative side, the heating medium is purposely exposed to process conditions in which scattered fumes are inadvertently deposited on the heating elements.

There is the problem as well as the risk that such heating elements may break and inadvertently come into contact with the chamber wall or with the chamber bottom. The fault current transmitted to the chamber wall poses a hazard to humans. In addition, the effect of the disturbed heating means ceases to have effect, which can result in an economic loss.

Such a loss arises, for example, when the heating means are used in vacuum chambers which, at best, are divided into functional areas, strung together to form a plant such as a continuous coater. The latter means an input and output side locks and vacuum chambers existing system for coating substrates. Such coating systems are highly productive and so far particularly sensitive to interference, since deviations in the process parameters such as temperature are not tolerable and malfunction can only be repaired consuming. Any productive disruption can cause further damage to sensitive technology. The productive operation is then interrupted for several hours.

As is known, the heating means are usually arranged in the vicinity of chamber walls. This may be the case either near the chamber bottom, the chamber walls or the chamber lid; Combinations of it included.

As used herein, a heater is at least a portion, area or the like that is provided to generate the heat, referred to herein as heating means. By a passive heating means, however, is to be understood such a section, etc., which represents one or more times either an extension of the heating means or directly adjacent to the heating means. In such a section, however, no heat is explicitly intended to be generated, but rather this passive heating means is used for holding and for supplying power to the heating heating means.

Together, heating means and passive heating means form the heater.

For example, according to the foregoing, a heating rod or strip of CFC is the heating medium. The remaining part for holding, etc., until then, that this has on the outside of the vacuum chamber an electrical Kantaktverbindung for connecting a line, is meant by the passive heating means.

CFC heating rods or strips are usually electrically supplied via two feedthroughs at the strip ends and for this purpose have two passive heating means. Between two bushings and contact strips and more Widerstandsheizstreifen can be connected in parallel. Advantageous arrangements of resistance heating strips are DE 10 2007 047 330 A1 removable.

Out DE 41 07 096 A1 is a protection for electrically heated vacuum furnaces, which detects an internal gas discharge known. A critical for the entire system arc can therefore arise from a spark out of current feedthroughs for heating elements and this is due to inserted high-frequency supply from their monitoring because of short-term occurrence not visible. Low-resistance interior linings made of graphite felt do not allow detection of a changed insulation resistance in the critical situation. But even in the heater passage attached auxiliary electrode, which is wound as a spiral around the current carrying the insulating conductor, this radio frequency only allow points at the bushings and only when it comes to the gas discharge to a short circuit between the auxiliary electrode and chamber. The protective effect is therefore achieved only under conditions such as ignition voltage and vacuum, which can lead to a gas discharge. A physical or mechanically induced electrical short circuit between heating medium and chamber would not be recognizable hereby; lowering the heating power is not the purpose of the solution sought.

From DE 199 24 106 A1 known circuit arrangement relates to the monitoring of Earth faults at a stove. This arrangement is designed for a three-phase powered heating system. In order to detect the ground fault with respect to the three phases used, chained inductances are provided in parallel with the voltage source per phase and heating means, whereas a solution for a one-phase heating medium is sought.

One out DE 201 22 527 U1 The resulting solution requires air convection for its function, which prohibits its use in vacuum technology.

Technical means are known to identify electrical fault currents and, as it were, to interrupt the line flow. So-called ground fault monitors, miniature circuit breakers and FI switches are familiar to the expert. What prevents them from using them arbitrarily, is for the high-current range, both the cost and the lack of opportunity with a signal of the fault state nachvollinnen a switched contact. The latter would be possible again with additional electrical components and costly.

It is the object of the invention to find a solution which improves the trouble-free operation of a heating medium in a vacuum chamber and in particular detects a defect of the heating medium.

This object is achieved by the invention according to claim 1.

Advantageous embodiments of the invention are the subject of dependent claims.

• – Versorgungsstromkreis für die Heizmittel,
• – Signalisierungsstromkreis für die Störung des Heizmittels,
• – Versorgungsstromkreis für angrenzende Heizmittel,
• – Versorgungsstromkreis für alternative Heizmittel (invers).

According to further advantageous forms of the embodiment of the invention, the normally open contacts of the electrical switch are used for switching circuits as follows:

• - supply circuit for the heating means,
• - signaling circuit for the disturbance of the heating medium,
• - supply circuit for adjacent heating means,
• - Supply circuit for alternative heating means (inverse).

The current-sensitive electrical switch should be similar in function to a circuit breaker or overcurrent switch. About its function, the switch is normally operated; its own (control) circuit and working contacts are closed. If too much current flows through the electrical switch, it opens.

These states are followed by the working contacts by opening or closing. So-called auxiliary contacts can be arranged directly next to the circuit breaker. The starting point is primarily the normally open contact, which opens when the electrical switch is actuated. This makes sense, in particular, if the defective heating means and also adjacent heating means are to be switched off. When signaling circuit opening or closing may be appropriate for the accident. This depends on how the accident detection system builds up. Ultimately, the change of state of the electrical switch is crucial and nachverarbeitbar. Alternative heating means come as a substitute into consideration. If a heating medium fails, a further heating means provided for the failure can in some cases fulfill the function further or alternatively. The latter is accordingly the supply voltage to part.

The electrical switch, as here to replace a circuit breaker, by an adequate component should be left to the expert. The advantage achieved so far with a circuit breaker, with about 2% of the rated heater current to cause the switch function, is decisive.

The general advantage of this solution should be emphatically helped to attention. Compared to conventional ground fault monitoring components, the cost advantage outweighs the simplicity, with which all requirements can be met. For the individual heating medium, this may at first seem insignificant, but the effect is more potent in systems in which more than ten times such heating means are installed.

The invention will be described in more detail with reference to an embodiment. This shows the 1 the arrangement with the vacuum chamber 1 and its chamber wall 2 ; the latter electrically conductive. To the heater 3 include the heating medium 4 and passive heating means 5 , The passive heating means 5 connect the heating medium 4 with the secondary coil 7 of the transformer 6 via lines 8th , The tap 9 at the secondary coil 7 is over the electrical switch 10 directed with the chamber wall 2 via an electrical line 8th connected. Is primarily the heating medium 4 disturbed as a result of a fracture, it contacts the chamber wall 2 , an excessive current flows through the electrical switch 10 which consequently changes its switching state and with it the working contacts 11 , A predetermined open contact 11 will cause the supply to the primary coil of the transformer 6 is interrupted. Another working contact 11 causes the signaling of the incident.

LIST OF REFERENCE NUMBERS

1

vacuum chamber

2

chamber wall

3

heater

4

heating

5

passive heating medium

6

transformer

7

secondary coil

8th

cables

9

tap

10

electrical switch (circuit breaker)

11

Normally Open

12

earth

Claims (8)

Arrangement for detecting a heating medium break, comprising - a vacuum chamber ( 1 ) with an electrically conductive inner chamber wall ( 2 ); A heating medium ( 4 ) using passive heating means ( 5 ) in the vacuum chamber ( 1 ) electrically isolated with a distance to the chamber wall ( 2 ) is held; - a transformer ( 6 ) with a secondary coil ( 7 ) for the electrical supply of the heating medium ( 4 ); - one between the chamber wall ( 2 ) and a tap ( 9 ) of the secondary coil ( 7 ) arranged current-sensitive electrically connected switch ( 10 ) with at least one contact ( 11 ) for interrupting the electrical supply of the heating means ( 4 ) in the event of a fracture-related short circuit between the heating means ( 4 ) and the chamber wall ( 2 ) and the resulting current flow through the switch ( 10 ). Arrangement according to claim 1, characterized in that the heating means ( 4 ) is strip-shaped and that the strips both to each other and to the chamber wall ( 2 ) are arranged in parallel spaced. Arrangement according to claim 1 or 2, characterized in that the current-sensitive electrical switch ( 10 ) is designed in the manner of a circuit breaker, which switches when exceeding a rated current within a tripping time. Arrangement according to one of claims 1 to 3, characterized in that the tap ( 9 ) the secondary coil ( 7 ) divides into two sub-coils so that over a sub-coil a proportion of the secondary voltage drops by 50%. Arrangement according to one of claims 1 to 4, characterized in that the heating means ( 4 ) is made of CFC (Carbon Fiber Reinforced Carbon). Arrangement according to one of claims 1 to 5, characterized in that the passive heating means ( 5 ) is made of molybdenum. Arrangement according to one of claims 1 to 6, characterized in that via the working contact ( 11 ) of the electrical switch ( 10 ) a power supply circuit, the primary coil of the transformer ( 6 ) feeds, is switched. Arrangement according to one of claims 1 to 7, characterized in that via a further working contact ( 11 ) of the electrical switch ( 10 ) a signaling circuit which detects the failure of the heating means ( 4 ) indicating function is switched.

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