DE102013211725A1 - Apparatus and method for forming a pipe - Google Patents

Abstract

The present invention relates to a device for shaping a tube (11), in particular a glass tube and a capillary tube, in a shaping section (66), the tube (11) having one or two open ends (24, 26), comprising a holding device (12) ) for holding and fixing the pipe (11) with a first fixing section (14) and a second fixing section (16), a heating pipe (38) which is arranged between the first and the second fixing section (14, 16) and which supports the pipe (11) ring-shaped and with which the pipe (11) can be heated, a gas source (34) for providing a gas flow, and a connecting piece (28) communicating with the gas source (34) for introducing the gas flow into the pipe (11) via one of the open ones Ends (24, 26). The invention also relates to a method and a computer program for reshaping the tube (11) and the tube (11) as such.

Description

The present invention relates to apparatus for forming a tube, in particular a glass tube and a capillary tube, in a forming section, the tube having one or two open ends. Furthermore, the invention relates to a method for forming a tube, in particular a tube and a capillary tube and a computer program for operating a control unit, with which the device can be controlled. Moreover, the invention also relates to the inventively formed tubes, especially glass tubes and the capillary tubes. When reference is made to pipes in the following description, glass pipes and in particular capillary tubes are equally meant. In capillary tubes, the problems that are solved with the invention occur to a particularly great extent, as will be described in more detail below.

The tubes, which are formed by means of the device and the method according to the invention, form the semifinished product, in particular for pipe sections used in the laboratory or in industrial production. The tubes may for example consist of plastic or glass or include these substances. The generic tubes are used when a liquid, which may also contain particles, must be conducted in a well-defined manner, for example in analytical chemistry. The general trend in detection tests of almost any kind is to keep the sample and reagent volumes as low as possible, which makes the detection tests cheaper and more efficient. Capillary tubes are particularly suitable for this purpose. Some detection tests rely on mixing the sample and reagent volumes in a reaction space where precipitation occurs depending on the presence of a property of interest in the sample. The precipitate is the qualitative proof that the sample has this property. However, it is also possible to make a statement as to the strength of the property via the amount of precipitate that forms. If the precipitate from the reaction space is introduced into a pipe, the fill level can be used for quantitative detection. In particular, when using a capillary tube for level determination, it is necessary to provide the capillary tube with a funnel-shaped portion or an extension in order to be able to introduce the precipitate from the reaction space into the capillary tube. The smaller the sample and reagent volume, the more accurate the extension must be made. Unevenness in the surface and deviations from the rotational symmetry and in the area of the enlargement can ensure that a certain amount of precipitation gets stuck in the extension and / or that the measured level does not correspond to reality. Consequently, the precision of the production of the extension, in particular of a capillary tube, is of decisive importance for the validity of a detection test carried out with the capillary tube. But in other applications, where a defined volume is to be introduced into the tube, the precision of the extension in terms of rotational symmetry and the surface condition of high importance.

In the glass industry, the extension of a tube can be manufactured in the following way: The tube is fixed to two fixing sections and then heated approximately midway between the two fixing sections with a gas burner in the forming section. The tube softens at the point where the capillary tube is heated and can be radially expanded or expanded by blowing in air to form a bubble. This process is well known in glassblowing. After the bubble has reached the desired size, it is allowed to cool the capillary tube and separates it in the area of the maximum diameter of the bubble, for example by scribing, so that two capillary tubes each with an extension arise. From the semifinished product thus arise two isolated components.

The gas burner used for heating can not uniformly heat the capillary tube over the circumference. In order nevertheless to achieve a rotationally symmetrical heating, the tube is rotated during the heating about the longitudinal axis. For this purpose, the tube must be rotated on both sides of the Umformabschnitts at exactly the same rotational speed. Even small differences in the number of revolutions lead to the fact that the bubble does not form rotationally symmetrical and has a so-called twist. In the area of the twist, spiral depressions form so that the inner surface of the bubble is not flat and some of the precipitate may get caught on the surface of the extension. The twist and surface properties in the area of the extension of known capillary tubes mean that the above-mentioned detection tests can not be carried out with the necessary accuracy, as already explained above.

The object of the present invention is therefore to provide an apparatus and a method with which a pipe, and in particular a pipe and a capillary tube can be produced with an enlargement, which have a significantly reduced twist and a more level surface than known pipes ,

The problem is solved by a device according to claims 1 and 2; Further preferred embodiments are the subject of the dependent claims.

The device according to the invention comprises a holding device for holding and fixing the tube with a first fixing section and a second fixing section, a heating tube arranged between the first and the second fixing section, which surrounds the tube in an annular manner and with which the tube can be heated, a gas source for providing a Gas stream, and a communicating with the gas source connector for introducing the gas flow into the pipe via one of the open ends. In the following, when referring to a tube, the relevant embodiments also refer to a glass tube and a capillary tube. Due to the fact that the tube is surrounded annularly by the heating tube, the tube can be heated rotationally symmetrically in the deformation section without the tube having to be rotated about the longitudinal axis. A forming section is to be understood as the section of the tube which expands measurably radially as a result of the heating. This alone can significantly reduce the twist of the bladder, so that the enlargement thus obtained is significantly more rotationally symmetrical and has a more level internal surface, which increases the quality of the test results, especially in analytical chemistry applications.

Furthermore, it is possible by the use of the annular heating tube to set a reproducible, known temperature profile along the longitudinal axis of the tube. If the tube is expanded radially in the forming section, the wall thickness of the tube in the forming section also changes. In general, it can be said that the wall or material thickness decreases as the bubble expands radially. Empirical measurements have shown that the same geometrical conditions in the forming section and in particular the same wall thicknesses set when the tube is heated with the same temperature profile. This is an important finding insofar as it makes it possible to close from the outer diameter to the inner diameter, which is for the control of the process, as will be explained later, important.

Furthermore, the gas source can be subjected to a pressure which leads to a bubble of the desired size in a forming process. By varying the pressure and the size of the bubble is changed, making this device particularly suitable for custom-made. It is not necessary to heat the pipe several times. On the one hand, this accelerates the forming or manufacturing process and also reduces the formation of a twist within the bladder, since the tube is thermally less heavily loaded in the forming section. Depending on the size of the pipe, the second open end, over which no gas stream is introduced, must not be closed, which further simplifies the forming or manufacturing process. The connector is designed so that it allows quick connection to existing pressure systems such as compressed air lines, etc.

The object is further achieved by a device for forming a closed tube, in particular a glass tube and a capillary tube, in a forming section, wherein the closed tube has a first and a second closed end and is subjected to an atmospheric pressure, comprising a holding device for holding and fixing of the closed tube with a first fixing section and a second fixing section, and a heating tube arranged between the first and the second fixing section, which annularly surrounds the closed tube and with which the closed tube can be heated. This device is operated with a closed tube, which is acted upon by an atmospheric pressure. Again, with the heating tube a rotationally symmetrical heating and a reproducible temperature profile can be provided. The overpressure causes the tube in the forming section to expand radially until equilibrium is established and radial expansion is stopped. A big advantage of this device is that the pipe does not have to be pressurized. A pressure source and a fitting are not required. For example, closed tubes with one, two, or three bars of atmospheric pressure can be used, each resulting in bubbles of precisely defined dimensions without the need to adjust pressure, thereby avoiding sources of error and simplifying the device. This device is suitable for the production of mass products with the same dimensions, which nevertheless have a twist-free extension.

Regardless of whether the tube is used with the two open ends or the tube which is exposed to an atmospheric pressure, it should again be pointed out that the tube does not have to be turned during forming. The tube must be clamped on both sides of the forming section and rotated there in known manufacturing processes. Even the smallest differences in the rotational speed lead to a twist when heating the tube. A transmission which almost completely synchronizes the rotational speeds at the two fixing sections is extremely expensive. Wear during operation could cancel the synchronization. These disadvantages are avoided according to the invention.

The device according to the invention is further developed in that a valve for selectively releasing or interrupting the gas flow is arranged in the pipe between the gas source and the connecting piece. The gas flow is used to set the pressure in the pipe. The valve makes it possible to increase the pressure when the tube has been heated for a certain time, whereby the formation of a twist can be further reduced. If a smaller or larger bubble is to be generated, a lower pressure can be set in the tube, so that bubbles of different sizes can be easily produced with the same device, which increases the flexibility of the device according to the invention. In order to reduce the dead volume largely, while the valve is arranged as close as possible to the connector.

Preferably, the valve is designed as a multi-way valve, with which the tube can be optionally vented. In addition to the advantages already set forth for the valve, the possibility of venting can additionally influence the production process of the bladder, as a result of which the production process can be carried out more quickly and reliably. In addition, it is advantageous if the multi-way valve is electrically switchable in order to be able to be integrated into a control or regulating circuit. In the closed pipe, no pressure change is possible, so that in the apparatus for forming the closed tube no valves are necessary.

In an advantageous embodiment, the heating tube is surrounded by an induction coil, wherein the heating tube consists of a material or comprises a material which can be heated with the induction coil. The use of an induction coil opens the possibility to bring the heating tube very precisely to the desired temperature, which is not possible, for example, with a gas burner. Consequently, the tube can be heated to a temperature which is optimal for forming the twist-free bubble. When using gas burners, the tube is heated more than necessary in many cases, which brings some adverse effects, especially when using borosilicate glasses. The excessive heating causes the evaporation of alkali borates, especially sodium borate, from the range which has been heated above the vaporization temperature of the alkali borates. On the one hand, the vaporized alkali borates diffuse into a somewhat cooler area in the near-surface region of the glass tube, which leads to an accumulation of alkali borates, which entails delamination processes and peel off small scale-like glass particles. On the other hand, the alkali borates deposit in significantly cooler areas on the surface and can mix with liquids that are passed through the glass tube, which can be very disadvantageous especially in analytical chemistry in detection tests. The use of induction coils makes it possible to heat the forming section only to the extent necessary for the forming. The evaporation of alkali borates is thus reduced to a harmless level. In addition, when the glass tube is heated to a high degree, as in the case of gas burners, there will be increased thermal stresses within the bubble. The thermal stresses mean that cracks can occur during the separation of the semi-finished products, for example due to breaking or cracking, so that the individual components thus obtained are scrap.

Furthermore, compared to induction coils, gas burners can be controlled significantly worse, which has the advantage that, with the use of induction coils, the process can be made slower and consequently more controlled, which leads to better results with respect to the geometries of the extension. Air currents do not interfere with inductive heating.

As an alternative to induction coils, it is possible to use resistance elements which also permit rotationally symmetrical heating and can be integrated into a control loop, but electrical lines are necessary which are exposed to high thermal loads and make replacement in the event of malfunction or cleaning difficult.

The material used is preferably a nickel-based alloy. A nickel-based alloy has a low tendency to scale and a relatively good dimensional stability at high temperature, so that the shape of the heating tube hardly changes during operation of the device. Any change in the shape of the heating tube also leads to uneven temperature distributions in the forming section, which in turn has a negative effect on the rotational symmetry of the bubble. Furthermore, it is preferred to keep the wall thickness of the heating tube and consequently the heat capacity as low as possible. This has the advantage that the temperature can be changed quickly and the manufacturing process can be made more accurate and faster. Furthermore, the heating tube should be well coupled to the high frequency field of the induction coil. An example of a preferred nickel-based alloy is 2.4952, which, in sum, best meets the stated requirements at the prevailing operating temperatures.

In a further preferred embodiment, the heating tube has an inner surface and one or two substantially perpendicular to the inner surface extending end faces, wherein the inner surface via a chamfer in the one end face or a first chamfer and a second chamfer merges into the two end faces. The design of the heating tube has a significant influence on the temperature distribution along the longitudinal axis of the tube during heating. Since glass is a poor conductor of heat, large temperature gradients arise between the heated and unheated portions of the pipe. The degree of heating is heavily dependent on the distance of the heating tube to the pipe. The chamfers ensure that the heating tube does not abruptly stop along the longitudinal axis of the tube, but that the distance to the tube gradually increases. As a result, the temperature gradient between the heated and unheated portions of the tube is less large, thereby reducing the thermal stresses, which increases the stability of the tube, which, as already stated, has a positive effect on the singulation process.

In a further development, the device according to the invention has an insulation for thermal shielding of the device. The insulation stabilizes the thermal conditions within the Umformabschnitts and is able to vorzuhalten a temperature of up to 900 ° C in the forming section. As a result, the energy required to operate the device or to heat the heating tube and the tube is reduced, so that the device can be operated more cheaply. It is advantageous if the insulation between the induction coil and the heating tube is arranged, whereby in addition to the thermal and an electrical separation between the heating tube and insulation is effected. As a result, the reliability of the device is increased. The insulation is preferably made of a ceramic material, whereby the insulation can also be used for positioning purposes of the heating tube. As will be explained later, it is important that the position of the heating tube does not change relative to the pipe in particular by the heating during the forming process, which is easy to achieve by a ceramic insulation. Furthermore, a ceramic insulation does not interfere with the interaction between the induction coil and the heating tube.

In a particularly preferred embodiment, the device has a temperature measuring device for measuring the temperature of the heating tube or in the forming section of the tube or the closed tube and for generating corresponding first signals. For this purpose, known and suitable measuring sensors can be arranged in the heating tube or in the forming section. Because there is up-to-date information regarding the temperature prevailing in the heating tube or in the forming section, the production process can be better controlled or regulated. The first signals are such that they can be read by a control unit. Since the temperature to which the tube or the closed during the manufacturing process of the bubble is heated, has an important influence on the quality of the resulting bubble and their surface properties, it is particularly well possible in this embodiment, the bubbles with the desired quality and in particular with to produce a high rotational symmetry and twist-free. It has been found that the temperature of the heating tube is better to measure than that of the pipe or the closed tube in the forming section, since in the latter case many disturbing influences can falsify the measurement results.

In this case, the temperature measuring device is preferably designed as a pyrometer. A pyrometer allows the non-contact determination of the temperature in the pipe or the heating tube from a distance, so that no measuring sensors must be used, which are exposed to a strong thermal load. The same applies to other components that cause the measuring sensors, such as electrical cables, etc. Furthermore, the temperature distribution in the forming section is not affected by the additional components. It is particularly preferred to design the pyrometer as a quotient pyrometer, whereby the influence of emissivity changes can be minimized.

Furthermore, the device has a measuring device for determining the radial extension of the tube and for generating corresponding second signals. The forming process of the bladder can thus be tracked, so that it is possible to stop it precisely when the radial extent of the bladder has exceeded a certain level. Further, it is possible to change other essential parameters for the forming process as a function of the instantaneous radial extent of the bubble, for example the volume flow or the pressure of the gas flow into the tube or the temperature of the heating tube. The number of bubbles produced with the desired dimensions is increased so that the rejects are reduced.

Preferably, the measuring device is designed as an optical measuring device. Optical measuring devices have proven themselves in such applications and are inexpensive and easy to use. For example, laser-based measuring devices can be used which provide the highest level of accuracy. It can be realized a kind of light barrier, which registers whether the radial extent of the bubble has reached or exceeded a certain level.

In this case, the measuring device is preferably designed as a camera. The camera can be chosen so that a large working distance at a low viewing angle allows becomes. The lower the viewing angle, the lower the necessary depth of focus, so that less expensive cameras can be used. In this case, the cameras preferably have a telecentric lens. The signals from the camera can be evaluated via an image processing program and converted, for example, into diameter data. Referring again to the applications of the tubes according to the invention in the laboratory and in particular in analytical chemistry, the course of the inner diameter in the extension is of crucial importance, whereas with the camera the outer diameter of the bubble can be determined. However, it has been found that the inner diameter and the outer diameter are in a fixed function to each other when a reproducible and defined temperature profile in the forming section and in particular along the longitudinal axis of the tube is adjusted. In this case, the outer diameter measured by the camera can be converted into the inner diameter with a simple mathematical correction. In this context, it is important that the distance between the forming section and the camera during the forming process always remains the same, which can be achieved particularly well with the ceramic insulation.

Preferably, the device comprises a lighting unit for providing light for illuminating the pipe. In particular, when the measuring device is designed to determine the radial extent of the tube as a camera or as another optical measuring device, it is of particular importance that the tube is uniformly illuminated at least at the point at which its radial extent is to be determined without disturbing reflections. The lighting unit can be designed so that the lighting conditions are optimally adapted to the particular optical measuring device used in order to obtain consistently reproducible measurement results.

In a further embodiment, the device has a reflection region for the purposeful reflection of the light provided by the illumination unit within the device. As already stated above, the heating tube surrounds the tube in an annular manner. Consequently, it is not readily possible to illuminate the tube directly in the forming section, without causing reflections that emanate from the tube and can falsify the measurement results. By means of a reflection region, on the one hand, the tube can be indirectly and yet adequately illuminated without there being any disturbing reflections; on the other hand, the illumination unit can be arranged flexibly spaced from the tube and from the heating tube, which simplifies the construction of the device.

Preferably, the fixing sections have grooves into which the pipe or the closed can be inserted and which are aligned along a longitudinal axis of the pipe. In this way, the fixing can be easily and effectively designed. The fact that the grooves are aligned along the longitudinal axis of the tube, the tube is in the fixed state virtually no stress on bending, which has a positive effect on the quality of the resulting bubble and its inner surface. In this case, the fixing each have a clamping unit, which act on the pipe so that the tube is fixable in the grooves. For example, the clamping units may apply a force to the tube such that the tube is forced into the grooves and fixed between the grooves and the tube due to the friction then created. The clamping units may, for example, be spring-loaded and therefore have a low overall height, so that they do not unnecessarily limit the area that can be detected by the camera. Prism grooves are preferably used, which are to be understood as grooves with a V-shaped cross section. The opening angle is typically 90 °. The prism grooves have the advantage that they themselves center the object to be clamped, in this case the pipe.

In a particularly preferred embodiment, the device according to the invention has a control unit, which is connectable to the multi-way valve, the heating tube, the temperature measuring device and the measuring device for determining the radial extent of the tube and the first signals and the second signals processed and the multi-way valve for introducing or Interrupting the flow of gas into the tube or for venting and the heating tube for heating the glass tube accordingly controls. In this embodiment, an automated control of the manufacturing process of the bubble can be realized. In this case, the outer diameter of the bubble can be detected almost continuously and the temporal change of the outer diameter compared with reference values. Depending on the result of the comparison, the temperature of the heating tube and / or the pressure in the tube can be changed by a corresponding control of the multiway valve. This control can produce a variety of bubbles of consistent quality with minimal waste. Furthermore, the control makes it possible to optimize the manufacturing process, for example by finding a specific temperature profile, which is passed through by the heating tube, so that the duration of the manufacturing process is minimized and thus its effectiveness is increased. Also, the control unit can take into account the inertia of the manufacturing process and determine a "braking point". Even if at the same time the pressure in the pipe degraded and the heating tube is turned off, this does not mean that the bubble diameter is not can still enlarge. In order to obtain a bubble with a certain diameter, it is therefore necessary to stop the heating and to reduce the pressure already when the desired diameter of the bubble has not yet been reached, which is to be described by the term "braking point". The provision of such a control unit is only necessary for the pipe with the two open ends, since the pipe can be formed with the closed ends without control.

• – Halten und Fixieren des Rohres mit einer Halteeinrichtung, die einen ersten Fixierabschnitt und einen zweiten Fixierabschnitt umfasst,
• – Erwärmen des Rohres mit einem zwischen dem ersten und dem zweiten Fixierabschnitt angeordneten Heizrohr, welches das Rohr ringförmig umschließt,
• – Bereitstellen eines Gasstroms mittels einer Gasquelle, und
• – Einleiten des Gasstroms in das Rohr über mindestens eines der offenen Enden mit einem mit der Gasquelle kommunizierenden Anschlussstück zum Einstellen des Drucks im Rohr, der eine radiale Erweiterung des Rohres im Umformabschnitt bewirkt.

The object is further achieved by a method for forming a tube, in particular a capillary tube, in a forming section, the tube having one or two open ends, comprising the following steps:

• Holding and fixing the tube with a holding device comprising a first fixing section and a second fixing section,
• Heating the tube with a heating tube arranged between the first and the second fixing section, which encloses the tube in an annular manner,
• - Providing a gas stream by means of a gas source, and
• - Introducing the gas flow into the tube over at least one of the open ends with a communicating with the gas source fitting for adjusting the pressure in the tube, which causes a radial expansion of the tube in the forming section.

The advantages and technical effects which are achieved with the method according to the invention correspond to those which have been described for the device according to the invention. In particular, it is possible to rotationally symmetrically heat the tube without rotation about the longitudinal axis, whereby the tube can be provided with a bubble, which is largely free of twist or torsion and has a substantially flat inner surface.

• – Messen der Temperatur des Heizrohres oder im Umformabschnitt des Rohres und Erzeugen von entsprechenden ersten Signalen mittels einer Temperaturmesseinrichtung,
• – Bestimmen der radialen Erstreckung des Rohres und Erzeugen von entsprechenden zweiten Signalen mittels einer entsprechend eingerichteten Messeinrichtung,
• – Verarbeiten der ersten Signale und der zweiten Signale mittels einer Regelungseinheit,
• – Ansteuern eines zwischen der Gasquelle und dem Anschlussstück angeordneten Mehrwegeventils mit der Regelungseinheit und wahlweises Freigeben oder Unterbrechen des Gasstroms in das Rohr oder wahlweises Entlüften des Rohres mittels des Mehrwegeventils, und
• – Ansteuern des Heizrohres mit der Regelungseinheit und wahlweises Erwärmen des Rohres mit dem Heizrohr.

The process according to the invention is developed with the following steps:

• Measuring the temperature of the heating tube or in the forming section of the tube and generating corresponding first signals by means of a temperature measuring device,
• Determining the radial extent of the tube and generating corresponding second signals by means of a suitably equipped measuring device,
• Processing the first signals and the second signals by means of a control unit,
• - Controlling a arranged between the gas source and the connector multi-way valve with the control unit and optionally releasing or interrupting the gas flow into the tube or selectively venting the tube by means of the multi-way valve, and
• - Actuation of the heating tube with the control unit and optional heating of the tube with the heating tube.

In this embodiment, an automated control of the forming process of the bubble can be realized. In this case, the outer diameter of the bubble can be detected almost continuously and the temporal change of the outer diameter compared with reference values. Depending on the comparison result, the temperature of the heating tube and / or the pressure in the tube can be changed by a corresponding control of the multiway valve. This control can produce a variety of bubbles of consistent quality with minimal waste. Furthermore, the inventive method in this embodiment makes it possible to optimize the manufacturing process, for example by finding a specific temperature profile, which is passed through by the heating tube, so that the duration of the forming process is minimized and thus its effectiveness is increased.

• – Halten und Fixieren des geschlossenen Rohres mit einer Halteeinrichtung, die einen ersten Fixierabschnitt und einen zweiten Fixierabschnitt umfasst, und
• – Erwärmen des geschlossenen Rohres mit einem zwischen dem ersten und dem zweiten Fixierabschnitt angeordneten Heizrohr, welches das geschlossene Rohr ringförmig umschließt Messen der Temperatur des Heizrohres oder im Umformabschnitt des Glasrohres,
• – Erzeugen von entsprechenden ersten Signalen mittels einer Temperaturmesseinrichtung,
• – Verarbeiten der ersten Signale mittels einer Regelungseinheit, und
• – Ansteuern des Heizrohres mit der Regelungseinheit und wahlweises Erwärmen des Glasrohres mit dem Heizrohr.

The object is further achieved with a method for forming a closed tube, in particular a capillary tube, in a forming section, wherein the closed tube has a first and a second closed end and is exposed to an atmospheric pressure, comprising the following steps:

• Holding and fixing the closed tube with a holding device comprising a first fixing section and a second fixing section, and
• Heating the closed tube with a heating tube arranged between the first and the second fixing section, which encloses the closed tube in an annular manner measuring the temperature of the heating tube or in the forming section of the glass tube,
• Generating corresponding first signals by means of a temperature measuring device,
• - Processing the first signals by means of a control unit, and
• - Actuation of the heating tube with the control unit and optional heating of the glass tube with the heating tube.

A significant advantage of this method is that the control is limited only to ensure that the temperature of the heating tube actually corresponds to the predetermined target temperature. Since the atmospheric pressure is already present in the closed tube, the closed tube only has to be heated with the defined, reproducible temperature profile so that bubbles of the same size are established.

• – eine Halteeinrichtung zum Halten und Fixieren des Rohres mit einem ersten Fixierabschnitt und einem zweiten Fixierabschnitt,
• – ein zwischen dem ersten und dem zweiten Fixierabschnitt angeordnetes Heizrohr, welches das Rohr ringförmig umschließt und mit dem das Rohr erwärmbar ist,
• – eine Gasquelle zum Bereitstellen eines Gasstroms, und
• – ein mit der Gasquelle kommunizierendes Anschlussstück zum Einleiten des Gasstroms in das Rohr über eines der offenen Enden,
• – ein Mehrwegeventil zum Einleiten oder Unterbrechen des Gasstroms in das Rohr oder zum Entlüften des Rohres,
• – eine Temperaturmesseinheit zum Messen der Temperatur des Heizrohres oder im Umformabschnitt des Rohres und Erzeugen von entsprechenden ersten Signalen,
• – eine Messeinrichtung zum Bestimmen der radialen Erstreckung des Rohres und Erzeugen von entsprechenden zweiten Signalen,

wobei das Computerprogramm Programmmittel zum Veranlassen eines Computers umfasst, die folgenden Schritte auszuführen, wenn das Computerprogramm auf dem Computer ausgeführt wird:

• – Messen der Temperatur des Heizrohres oder im Umformabschnitt des Rohres und Erzeugen von entsprechenden ersten Signalen mittels der Temperaturmesseinrichtung,
• – Bestimmen der radialen Erstreckung des Rohres und Erzeugen von entsprechenden zweiten Signalen mittels der Messeinrichtung,
• – Verarbeiten der ersten Signale und der zweiten Signale mittels der Regelungseinheit,
• – Ansteuern des Mehrwegeventils mit der Regelungseinheit und wahlweises Freigeben oder Unterbrechen des Gasstroms in das Rohr oder wahlweises Entlüften des Rohres mittels des Mehrwegeventils, und
• – Ansteuern des Heizrohres mit der Regelungseinheit und wahlweises Erwärmen des Rohres mit dem Heizrohr.

Furthermore, the object is achieved by a computer program for operating a control unit with which a device for forming a tube, in particular a capillary tube, can be regulated in a forming section, the device comprising:

• A holding device for holding and fixing the tube with a first fixing section and a second fixing section,
• A heating tube arranged between the first and the second fixing section, which surrounds the tube in an annular manner and with which the tube can be heated,
• A gas source for providing a gas flow, and
• A connector communicating with the gas source for introducing the gas flow into the tube via one of the open ends,
• A multi-way valve for introducing or interrupting the gas flow into the pipe or for venting the pipe,
• A temperature measuring unit for measuring the temperature of the heating tube or in the forming section of the tube and generating corresponding first signals,
• A measuring device for determining the radial extent of the tube and generating corresponding second signals,

wherein the computer program comprises program means for causing a computer to perform the following steps when the computer program is run on the computer:

• Measuring the temperature of the heating tube or in the forming section of the tube and generating corresponding first signals by means of the temperature measuring device,
• Determining the radial extent of the tube and generating corresponding second signals by means of the measuring device,
• Processing the first signals and the second signals by means of the control unit,
• - Controlling the multi-way valve with the control unit and optional release or interruption of the gas flow into the tube or optional venting of the tube by means of the multi-way valve, and
• - Actuation of the heating tube with the control unit and optional heating of the tube with the heating tube.

By means of the computer program according to the invention, an automated regulation of the forming process of the bladder can be realized. In this case, the outer diameter of the bubble can be detected almost continuously and the temporal change of the outer diameter compared with reference values. Setpoints for the outer diameter can be entered via the computer. Depending on the result of the comparison, the temperature of the heating tube can be changed and / or the pressure introduced in the tube, the mass flow of the gas stream changed or interrupted or the tube is changed by a corresponding control of the multi-way valve. This control can produce a variety of bubbles of consistent quality with minimal waste. Furthermore, the computer program according to the invention makes it possible to optimize the production process, for example by finding a specific temperature profile, which is passed through by the heating tube, so that the duration of the manufacturing process is minimized and thus its effectiveness is increased. Very much data can be collected and processed so that the manufacturing process can be run through with a high degree of reproducibility. Furthermore, all processed manufacturing processes can be documented and evaluated by the computer. Such a computer program is not necessary for the closed pipe.

berechnet und der maximale Wert ΔR_max = MAX(ΔR_i;rel) gesucht wird, wobei der Wert ΔR_max 5% oder weniger, insbesondere 3% oder weniger beträgt. Wenn eine Erweiterung diese Bedingung erfüllt, kann sie als im Wesentlichen twist- oder torsionsfrei gewertet werden. Ein Rohr mit einer idealen Erweiterung weist einen Wert von ΔR_max = 0% auf. Glasrohre und insbesondere Kapillarröhrchen mit einer derartigen Erweiterung eignen sich ganz besonders für den Einsatz bei in der analytischen Chemie, da sie aufgrund ihrer hohen Präzision bezüglich des Verlaufs und der Oberflächeneigenschaften der Erweiterung eine hohe Verlässlichkeit und Genauigkeit von Nachweistests unterstützen.Furthermore, the invention relates to a tube and in particular a capillary tube having a longitudinal axis and an extension, wherein the extension in a selectable plane passing through the longitudinal axis has an integer number of i> 1 upper radii and lower radii and for each number i the value

calculated and the maximum value ΔR _max = MAX (ΔR _{i; rel} ) is sought, wherein the value ΔR _{max is} 5% or less, in particular 3% or less. If an extension meets this condition, it can be considered essentially torsion-free or torsion-free. A pipe with an ideal extension has a value of ΔR _max = 0%. Glass tubes and in particular capillary tubes with such an extension are particularly suitable for use in analytical chemistry, since they support a high reliability and accuracy of detection tests due to their high precision in terms of the course and the surface properties of the extension.

Preferably, the tube or closed tube is borosilicate glass, with the forming section and unformed sections having substantially the same alkali borate concentration. In other words, the borosilicate glass tubes of the invention have no zones of depletion or accumulation of alkali borate. This is in particular a consequence of the forming process according to the invention, in which due to the use of the annular heating tube instead of gas burners, the tube is heated only to the extent necessary for the forming process. The temperatures required for this purpose are approximately between 800 to 900 ° C, well below the evaporation temperature of the alkali metal borates, so that there is no or no significant depletion or accumulation of alkali borates within the glass tube. No delamination zone or condensation zone is formed, which prevents peeling of flaky glass particles or migration of alkali borates into the liquids conducted in the pipe.

The invention will be explained below with reference to a preferred embodiment. Show it

1 A first embodiment of a device according to the invention for forming a tube based on a principal side view,

2 A second embodiment of the device according to the invention for forming a closed tube, also with reference to a side view,

3 a comparison of a tube having an ideal course both with respect to the longitudinal axis and with respect to a plane passing through the maximum diameter, with a tube having a twist,

4 an isolated component, which comes from the in 3 shown tube according to the invention has been produced.

In 1 is an embodiment of a device according to the invention 10 ₁ for forming a tube 11 illustrated by a schematic diagram. The device 10 ₁ comprises an approximately U-shaped holding device 12 for holding and fixing the pipe 11 with a first fixing section 14 and a second fixing section 16 , each one a groove 18 have, in which the pipe 11 can be introduced. The grooves 18 are aligned so that they are along a longitudinal axis L of the tube 11 as closely aligned as possible so that the pipe 11 can be fixed with the lowest possible bending load. The first fixing section 14 further comprises a first clamping unit 20 and the second fixing section 16 includes a second clamping unit 22 with which the pipe 11 in the groove 18 pressed and fixed without the tube 11 is damaged. The pipe 11 has a first and a second open end 24 . 26 on, being at the first open end 24 a connector 28 is attached, that over a channel 30 with a valve 32 and a gas source 34 is connected, so that gas from the gas source 34 in the pipe 11 can be initiated. As the gas, an inert gas or air may be used, and the gas should be dried to largely suppress condensation and reaction processes. The valve 32 is preferably as a multi-way valve 36 executed, so that the pressure in the pipe 11 can be changed quickly. The second open end 26 may be closed in a manner not shown, but this is not mandatory.

Approximately in the middle between the two fixing sections 14 . 16 is a heating pipe 38 arranged, which the pipe 11 encloses annularly. The heating tube 38 has an inner surface 40 leading to the pipe 11 pointing, and two faces 42 on, which is substantially perpendicular to the inner surface 40 run. The inner surface 40 goes over one chamfer each 44 in the two faces 42 above. In the example shown, the chamfer has 44 a chamfer angle of about 45 °. Alternatively, a rounding can be provided, with which the inner surface 40 in the frontal areas 42 passes. The heating tube 38 comprises or consists of a material derived from an induction coil 43 can be heated, which is the heating tube 38 encloses radially. Between the induction coil 43 and the heating tube 38 is an insulation 46 attached to the heating pipe 38 completely surrounds and the heating pipe 38 partially overlapped in the direction of the longitudinal axis L of the tube (see. 2 ).

Furthermore, the device comprises 10 ₁ a temperature measuring device 48 for measuring the temperature of the heating tube or the tube 11 , In the example shown, the temperature measuring device 48 as a pyrometer 50 designed so that the temperature of the heating tube or pipe 11 can be determined without contact and over a certain distance. On the pyrometer 50 opposite side of the device 10 ₁ is a measuring device 52 for determining the radial extent of the tube 11 arranged as an optical measuring device 54 and concretely as a camera 56 is trained. The camera 56 is arranged so that it has the smallest possible angle to the longitudinal axis L of the tube 11 encloses to the outside diameter of the pipe 11 to be able to determine as accurately as possible. The camera points to this 56 a telecentric lens. Furthermore, the second clamping unit 22 on the same side of the device 10 _{1 is} arranged like the camera 56 , especially flat, around the pipe 11 concerning the camera 56 to obscure as little as possible.

In addition, the device has 10 ₁ a lighting unit 58 for providing light for illuminating the tube 11 on, so the camera 56 the radial extent and in particular the diameter of the tube 11 can capture well. Further, at the first fixing portion 14 which of the camera 56 opposite, a reflection area 60 attached to the lighting unit 58 is directed and which is provided with a light color. Thus, the pipe becomes 11 Illuminated indirectly, so no disturbing reflections on the tube 11 arise. Furthermore, the light color increases the contrast, leaving the camera 56 the diameter of the pipe 11 can capture well.

Furthermore, it is a control unit 62 provided by electrical lines 64 with the camera 56 , the induction coil 43 , the pyrometer 50 and the multiway valve 36 is connected and with which the forming process of the pipe 11 can be regulated. If advantageous, can also be a wireless connection between the camera 56 , the induction coil 43 , the pyrometer 50 , the multiway valve 36 and the control unit 62 be provided. The transformation process is as follows:
The pipe 11 gets into the grooves 18 introduced and with the clamping units 20 . 22 in the two fixing sections 14 . 16 fixed. Subsequently, the induction coil 43 activated, so that the heating tube 38 and therefore also the pipe 11 heated. The multiway valve 36 is placed in a position so that the gas flow from the gas source 34 in the pipe 11 released and the pressure in the pipe 11 will be changed. The temperatures of the heating tube 38 and / or the pipe 11 be with the pyrometer 50 monitored, the pyrometer 50 generates first signals which correspond to the measured temperature. The radial extent and in particular the diameter of the tube 11 be with the camera 56 determines what the camera does 56 recorded images are evaluated by an image editing software and converted into second signals corresponding to the outer diameter of the tube 11 correspond.

With increasing warming the pipe becomes 11 always softer and expanded radially outward by the pressure, so that a bubble is created. The area which is expanded by the pressure and in which the radial extent of the tube 11 changes, is intended as a forming section 66 To be defined. The camera 56 is aligned to capture the maximum outer diameter of the bladder.

The first signals corresponding to the outer diameter of the bubble and the temperature of the heating tube or the tube 11 in the forming section 66 corresponding second signals are sent to the control unit 62 transmitted and evaluated there. The heating tube 38 as long as from the induction coil 43 activated until a first temperature is reached. Then the control unit checks 62 whether the bladder has reached a first maximum outer diameter. If this is not the case, the first temperature is kept. When the first maximum diameter is reached, the induction coil becomes 43 switched off and the pressure in the pipe 11 reduced by a corresponding control of the multi-way valve to ambient pressure. Due to the inertia of the system, the maximum diameter will continue to increase until after a certain waiting time a second maximum diameter is reached. Then the pressure is increased again and interrupted and the induction coil 43 turned on and off until that of the camera 56 determined maximum outer diameter deviates less than a predetermined amount of the desired maximum outer diameter. Then the transformation process is terminated and the determined data is archived.

In 2 is a second embodiment of the device according to the invention 10 ₂ , but with which only closed tubes 67 with a first and a second closed end 68 . 70 can be edited. The essential structure of the device 10 ₂ according to the second embodiment corresponds to the first embodiment 10 ₁ . But because the closed pipes 67 already subjected to an atmospheric pressure and due to the closed ends 68 . 70 by means of a gas flow no influence on the pressure in the closed tube 67 should and can be taken, will not be a gas source 34 and therefore no connector 28 needed. As already mentioned, automatically creates a bubble with a certain radial extent, if a defined, reproducible temperature profile of the heating tube 38 provided. In this respect, it is also not necessary to have a measuring device 52 for determining the radial extent of the closed tube 67 provided. In the example shown, the device comprises 10 ₂ the temperature measuring device 48 , which serves as a control, the set temperature with the actual temperature of the heating tube 38 using the control unit 62 to compare and intervene if necessary. As I said, the device includes 10 ₁ according to the first embodiment, the same components as the device according to the second embodiment 10 ₂ , but still has the additional components discussed above. In this respect, it is also possible to have a closed tube 67 with the device 10 ₁ to transform the first embodiment, including the connector 28 not with the closed pipe 67 is connected and the control unit 62 either completely switched off or adjusted so that they only have the temperature in the heating tube 38 monitored and corrected if necessary.

3 shows a comparison of a tube 11 _i , which has an ideal course both with respect to the longitudinal axis L and with respect to a plane passing through the maximum diameter plane E, with a tube 11 _T , which has a twist. The pipe 11 _i , which has an ideal course, is shown by a solid line, while the tube 11 _T is provided with a twist with a dashed line. For clarity, a first upper radius R _{1, o} , relative to the illustrated plane E, a second upper radius R _{2, o} , a first lower radius R _{1, u} and a second lower radius R _{2, u are} once for the tube 11 _i with an ideal course and once for the tube 11 _T marked with twist. For illustrative purposes, the respective radii are for the pipe with ideal gradient and twist 11 _i and 11 _T spaced apart from each other, but this does not change the following statement: It can be seen that regardless of the distance to the plane E, which is due to the maximum diameter of the tube 11 _i with ideal course of the first upper and the first lower radius R _{1, o} , R _{1, u} and the second upper and the second lower radius R _{2, o} , R _{2, u of} the tube 11 _i with ideal course are the same, while the first upper and the first lower radius R _{1, o} , R _{1, u} and the second upper and the second lower radius R _{2, o} , R _{2, u of} the tube 11 _T with Twist are sometimes very different. In 3 an isolated component is shown, which by separating the pipe 11 obtained in the plane E which passes through the maximum diameter is obtained. It can be seen that it is the tube 11 _T with twist is difficult to decide is where the pipe 11 is to be separated, since the plane E, which extends through the maximum diameter, in this case is not perpendicular to the longitudinal axis L.

The tube according to the invention 11 Can be made so precise that it is drawing the pipe 11 _i corresponds to ideal course, so that in 3 not closer between the pipe according to the invention 11 and the tube 11 _i is discriminated with an ideal curve. The tube according to the invention in this case has an extension, wherein the radii R _{i, o} and R _{i, u} satisfy the following condition:

in which ΔR _max = MAX (ΔR _{i; rel} ) and ΔR _{max is} 5% or less, more preferably 3% or less. In the 3 shown radii R _{1, o} and R _{1, u} and R _{2, o} and R _{2, u} extend in the same plane, which runs through the longitudinal axis, but this is not necessarily the case, but is advantageous for metrological reasons. The in 3 Course shown also applies to the closed tube 67 to.

In 4 an isolated component is shown, as it finds in practice mainly used by separating the in 3 illustrated tube 11 . 67 has been obtained along the plane E.

LIST OF REFERENCE NUMBERS

10, 101, 102

 contraption

11

 pipe

12

 holder

14

 first fixing section

16

 second fixing section

18

 groove

20

 first clamping unit

22

 second clamping unit

24

 first open end

26

 second open end

28

 connector

30

 channel

32

 Valve

34

 gas source

36

 Multi-way valve

38

 heating pipe

40

 inner surface

42

 face

44

 chamfer

45

 induction coil

46

 insulation

48

 Temperature measuring device

50

 pyrometer

52

 measuring device

54

 optical measuring device

56

 camera

58

 lighting unit

60

 reflection unit

62

 control unit

64

 electrical line

66

 forming section

67

 closed pipe

68

 first closed end

70

 second closed end

e

 level

L

 longitudinal axis

R _{1, o}

 first upper radius

R _{1, u}

 first lower radius

R _{2, o}

 second upper radius

R _{2, u}

 second lower radius

Claims (25)

Device for forming a tube ( 11 ), in particular a glass tube and Kapillarröhrchens, in a forming section ( 66 ), whereby the pipe ( 11 ) one or two open ends ( 24 . 26 ), comprising - a holding device ( 12 ) for holding and fixing the tube ( 11 ) with a first fixing section ( 14 ) and a second fixing section ( 16 ), - one between the first and the second fixing section ( 14 . 16 ) arranged heating tube ( 38 ), which the pipe ( 11 ) annularly surrounds and with which the pipe ( 11 ) is heatable, A gas source ( 34 ) for providing a pressure in the pipe ( 11 ), and - one with the gas source ( 34 ) communicating connector ( 28 ) for introducing the gas flow into the tube ( 11 ) over one of the open ends ( 24 . 26 ). Device for forming a closed tube ( 67 ), in particular a glass tube and a capillary tube, in a forming section ( 66 ), wherein the closed tube ( 67 ) a first and a second closed end ( 68 . 70 ) and is exposed to an atmospheric pressure, comprising - a holding device ( 12 ) for holding and fixing the closed tube ( 67 ) with a first fixing section ( 14 ) and a second fixing section ( 16 ), and - between the first and the second fixing section ( 14 . 16 ) arranged heating tube ( 38 ), which the closed tube ( 67 ) surrounds annular and with which the closed tube ( 67 ) is heated. Apparatus according to claim 1, characterized in that between the gas source ( 34 ) and the connector ( 28 ) a valve ( 32 ) for selectively releasing or interrupting the gas flow into the pipe ( 11 ) is arranged. Device according to claim 3, characterized in that the valve ( 32 ) as a multiway valve ( 36 ) is designed, with which the pipe ( 11 ) can be optionally vented. Device according to one of the preceding claims, characterized in that the heating tube ( 38 ) of an induction coil ( 43 ) is surrounded and the heating tube ( 38 ) consists of a material or comprises a material which is connected to the induction coil ( 43 ) is heated. Apparatus according to claim 5, characterized in that the material is a nickel-based alloy. Device according to one of the preceding claims, characterized in that the heating tube ( 38 ) an inner surface ( 40 ) and one or two substantially perpendicular to the inner surface ( 40 ) running faces ( 42 ), wherein the inner surface ( 40 ) over a chamfer ( 44 ) in the one end face ( 42 ) or over a first chamfer ( 44 ₁ ) and a second chamfer ( 44 ₂ ) in the two end faces ( 42 ) passes over. Device according to one of the preceding claims, characterized in that the device is an insulation ( 46 ) for thermal shielding of the device ( 10 ) having. Device according to claim 8, characterized in that the insulation ( 46 ) between the induction coil ( 43 ) and the heating tube ( 38 ) is arranged. Device according to one of the preceding claims, characterized in that the device is a temperature measuring device ( 48 ) for measuring the temperature of the heating tube ( 38 ) or in the forming section ( 66 ) of the pipe ( 11 ) or the closed tube ( 67 ) and for generating corresponding first signals. Apparatus according to claim 10, characterized in that the temperature measuring device ( 48 ) as a pyrometer ( 50 ) is trained. Device according to Claim 1 or one of Claims 5 to 11, characterized in that the device has a measuring device ( 52 ) for determining the radial extent of the tube ( 11 ) and for generating corresponding second signals. Apparatus according to claim 12, characterized in that the measuring device ( 52 ) as an optical measuring device ( 54 ) is trained. Apparatus according to claim 13, characterized in that the measuring device ( 52 ) as a camera ( 56 ) is trained. Device according to claim 13 or 14, characterized in that the device ( 10 ) a lighting unit ( 58 ) for providing light for illuminating the tube ( 11 ). Device according to claim 15, characterized in that the device ( 10 ) a reflection area ( 60 ) for the targeted reflection of the illumination unit ( 58 ) provided light within the device ( 10 ) having. Device according to one of the preceding claims, characterized in that the fixing sections ( 14 . 16 ) Grooves ( 18 ) into which the pipe ( 11 ) or the closed tube ( 67 ) and along a longitudinal axis (L) of the tube ( 11 ) or the closed tube ( 67 ) are aligned. Apparatus according to claim 17, characterized in that the fixing sections ( 14 . 16 ) one clamping unit each ( 20 . 22 ), which on the pipe ( 11 ) or on the closed tube ( 67 ) act that the pipe ( 11 ) or the closed tube ( 67 ) is fixable in the grooves. Apparatus according to claim 4 and 10 or 11 and any one of claims 12 to 15, characterized characterized in that the device ( 10 ) a control unit ( 62 ), which with the multi-way valve ( 36 ), the heating tube ( 38 ), the temperature measuring device ( 48 ) and the measuring device ( 52 ) for determining the radial extent of the tube ( 11 ) and the first signals and the second signals are processed and the multi-way valve ( 36 ) for introducing or interrupting the gas flow into the tube ( 11 ) or for venting and the heating tube ( 38 ) for heating the tube ( 11 ) accordingly controls. Method for forming a glass tube ( 11 ), in particular a capillary tube, in a forming section ( 66 ), whereby the pipe ( 11 ) has one or two open ends, comprising the following steps: holding and fixing the glass tube ( 11 ) with a holding device ( 12 ), which has a first fixing section ( 14 ) and a second fixing section ( 16 ), - heating the glass tube ( 11 ) with a between the first and the second fixing section ( 14 . 16 ) arranged heating tube ( 38 ), which the pipe ( 11 ) encloses annularly, - providing a gas stream by means of a gas source ( 34 ), and - introducing the gas flow into the tube ( 11 ) over at least one of the open ends with one with the gas source ( 34 ) communicating connector ( 28 ) for adjusting the pressure in the pipe ( 11 ), which is a radial extension of the tube ( 11 ) in the forming section ( 66 ) causes. The method of claim 19, further comprising the steps of: - measuring the temperature of the heating tube ( 38 ) or in the forming section ( 66 ) of the glass tube ( 11 ) and generating corresponding first signals by means of a temperature measuring device ( 48 ), - determining the radial extent of the glass tube ( 11 ) and generating corresponding second signals by means of a suitably equipped measuring device ( 52 ), - processing the first signals and the second signals by means of a control unit ( 62 ), - driving one between the gas source ( 34 ) and the connector ( 28 ) arranged multi-way valve with the control unit ( 62 ) and selectively releasing or interrupting the flow of gas into the tube ( 11 ) or optional venting of the glass tube ( 11 ) by means of the multi-way valve, and - driving the heating tube ( 38 ) with the control unit ( 62 ) and optional heating of the glass tube ( 11 ) with the heating tube ( 38 ). Method for forming a closed tube ( 67 ), in particular a capillary tube, in a forming section ( 66 ), wherein the closed tube ( 67 ) a first and a second closed end ( 68 . 70 ) and is exposed to an atmospheric pressure, comprising the following steps: - holding and fixing the closed tube ( 67 ) with a holding device ( 12 ), which has a first fixing section ( 14 ) and a second fixing section ( 16 ), and - heating the closed tube ( 67 ) with a between the first and the second fixing section ( 14 . 16 ) arranged heating tube ( 38 ), which the closed tube ( 67 ) encloses annularly, - measuring the temperature of the heating tube ( 38 ) or in the forming section ( 66 ) of the glass tube ( 11 ) and generating corresponding first signals by means of a temperature measuring device ( 48 ), - processing the first signals by means of a control unit ( 62 ), and - controlling the heating tube ( 38 ) with the control unit ( 62 ) and optional heating of the glass tube ( 11 ) with the heating tube ( 38 ). Computer program for operating a control unit ( 62 ), with which a device ( 10 ) for forming a tube ( 11 ), in particular a glass tube and a capillary tube, in a forming section ( 66 ), the device comprising: - a holding device ( 12 ) for holding and fixing the tube ( 11 ) with a first fixing section ( 14 . 16 ) and a second fixing section ( 14 . 16 ), - one between the first and the second fixing section ( 14 . 16 ) arranged heating tube ( 38 ), which the pipe ( 11 ) annularly surrounds and with which the pipe ( 11 ) is heatable, - a gas source ( 34 ) for providing a gas stream, and - one with the gas source ( 34 ) communicating connector ( 28 ) for introducing the gas flow into the tube ( 11 ) over one of the open ends, - a multi-way valve ( 36 ) for introducing or interrupting the gas flow into the tube ( 11 ) or for venting the pipe ( 11 ), - a temperature measuring unit for measuring the temperature of the heating tube ( 38 ) or in the forming section ( 66 ) of the pipe ( 11 ) and generating corresponding first signals, - a measuring device ( 52 ) for determining the radial extent of the tube ( 11 ) and generating corresponding second signals, the computer program comprising program means for causing a computer to perform the following steps when the computer program is executed on the computer: - measuring the temperature of the heating tube ( 38 ) or in the forming section ( 66 ) of the pipe ( 11 ) and generating corresponding first signals by means of the temperature measuring device ( 48 ), - determining the radial extent of the tube ( 11 ) and generating corresponding second signals by means of the measuring device ( 52 ) Processing of the first signals and the second signals by means of the control unit ( 62 ), - controlling the multi-way valve with the control unit ( 62 ) and selectively releasing or interrupting the flow of gas into the tube ( 11 ) or optional venting of the glass tube ( 11 ) by means of the multi-way valve, and - driving the heating tube ( 38 ) with the control unit ( 62 ) and optional heating of the tube ( 11 ) with the heating tube ( 38 ). Pipe ( 11 ) or closed pipe ( 67 ), in particular glass tube and capillary tube, having a longitudinal axis (L) and an extension, wherein the extension in a selectable through the longitudinal axis (L) extending plane has an integer number of i> 1 upper radii and lower radii and for each number i of value

calculated and the maximum value ΔR _max = MAX (ΔR _{i; rel} ) is sought, wherein the value ΔR _{max is} 5% or less, in particular 3% or less. Pipe ( 11 ) or closed pipe ( 67 ) according to claim 24, characterized in that the tube ( 11 ) or the closed tube ( 67 ) consists of borosilicate glass and the forming section ( 66 ) and the non-reshaped portions have substantially the same alkali borate concentration.

Images