FR2825359A1 - DEVICE FOR REDUCING THE FLOW OF GAS IN THE STRETCH DUCT AROUND THE STRETCH CORNET, WHEN MANUFACTURING GLASS TUBES - Google Patents

Abstract

The invention relates to a device for reducing the flow of gas in the stretching channel in the region of the stretching horn. The device comprises at least one nozzle (2) and at least one constriction (5) arranged in the drawing channel. The invention also relates to a method for reducing the flow of gas in the drawing channel, around the horn. stretching. According to said method, the tube section (3) is enveloped in hot gas delivered by a nozzle (2) at the end or inside the drawing channel (1).

Description

adjustable. Device for reducing the flow of gas in the duct

  The present invention relates to a device for reducing the flow of gas around the drawing horn during the manufacture of glass tubes. The invention also relates to a method making

use of the device.

  For the manufacture of glass tubes according to the Danner process, a slightly inclined tube is used as a drawing tool, which is rotated slowly, known as the "Danner rod", on which a continuous bead of molten glass. At the lower end of the cane, that is to say at the level of the cane head, the glass is removed by forming the drawing horn, a cavity being formed by introducing air through the hollow shaft of the rod. After being brought into a horizontal plane, the tube in the course of solidification is conveyed by a conveyor belt with rollers to the drawing machine, at the outlet of which it is cut into

sections by shearing.

  During the production of glass tubes according to the Danner process, air is sucked in by chimney effect at the end of the essential drawing channel, which air circulates around the drawing horn before the exit of the muffle system. The dimensioning process is negatively influenced by variations

of air flow.

  The manufacturing requirements for tube precision are high. The accuracy of a glass tube is characterized by a fluctuation in the outside diameter of s + 0.7%, related to the nominal diameter. Usually in glass tubes produced by the Danner process, you cannot get fluctuations

<+ 1%.

  From there, the object of the present invention is to provide a device and an economical method for manufacturing precision glass tubes, the air flow in the drawing channel, around

  of the drawing horn being greatly reduced.

  This object is achieved in accordance with the invention using a device for limiting the flow of air in the drawing channel, S around the drawing horn, which comprises at least one nozzle and at

  minus a throttle arranged in the drawing channel.

  The device according to the invention makes it possible to economically manufacture precision tubes. The process of setting the tube in the drawing channel, surprisingly, is positively influenced by the device according to the invention, thanks to a constancy

  in the high time of isotherms in the region of the stretching horn.

  The device according to the invention makes it possible to obtain precision tubes with a fluctuation in the outside diameter s + 0.7%, relative to the

nominal outside diameter.

  1S According to a preferred embodiment of the invention, the nozzle and the throttle are arranged at the end of the drawing channel. With this arrangement, good results are obtained in the

manufacture of precision tubes.

  According to another preferred embodiment of the invention, the nozzle is shaped as a flat nozzle. With the flat nozzle, very good results are obtained in the manufacture of tubes. préclslon. According to another preferred embodiment of the invention, the constriction is in the form of a diaphragm

slotted.

  According to the invention, there is provided a method for reducing the flow of gas in the drawing channel, around the drawing horn, according to which the tube section is bathed in hot gas coming out of a nozzle. end or inside the drawing channel. The method according to the invention makes it possible to economically manufacture precision glass tubes. The process of dimensioning the tube in the drawing horn, surprisingly, is positively influenced by the method according to the invention, by a constancy in

  the high time of the isotherms in the region of the stretching horn.

  With the method according to the invention, it is possible to produce precision glass tubes with a fluctuation in the outside diameter

  + 0.7%, based on nominal diameter.

  According to a preferred embodiment of the invention, the temperature of the gas leaving the nozzle is equal to the temperature of the glass, corresponding to a viscosity in a range from to 108 Pa. S. With such temperatures you get good

  results in the manufacture of precision glasses.

  According to another preferred embodiment of the invention, the speed of flow of the gas is greater than the speed of entry of air into the drawing horn. This speed is advantageous

  for the manufacturing process of precision tubes.

  The invention will be described in more detail in the following in

referring to the drawing.

  FIG. 1 single represents the drawing process according to Danner. The drawing channel (1) has at its end a flat nozzle (2) for the air flow. An air curtain (4) is thus formed. The tab section (3) is enveloped by the air curtain (4). At the end, the cross section of the drawing channel (1) is reduced by a

  constriction in the form of a slit diaphragm (5).

  Thanks to an air curtain (4) with a given air flow speed, the drawing channel (1) is sealed. The air flow speed is greater than the speed of air entering the drawing channel (1). At the end of the drawing channel (1) or inside a segment thereof, hot air exits through a flat nozzle (2) and surrounds the section of tube (3). The cross section of the drawing channel (1) is limited in the horizontal direction by

adapted devices (5).

Claims (7)

  1. Device for reducing the flow of gas in the drawing channel, in the region of the drawing horn, characterized in that it comprises at least one nozzle (2) and at least one constriction (5) arranged at the end of the drawing channel. 2. Device according to claim 1, characterized in that the   nozzle is arranged at the end of the drawing channel (1).   3. Device according to claim 1 or 2, characterized in that the nozzle (2) is shaped as a flat nozzle (2) and, with the gas flow, forms a gas curtain .;   4. Device according to any one of claims 1 to 3,   characterized in that the constriction (S) is shaped as a diaphragm slot (5).   5. Method for reducing the flow of gas in the drawing channel, around the drawing horn, characterized in that the tube section (3) is enveloped in hot gas supplied by a nozzle (2) to   the end or inside the drawing channel (1).   6. A method according to claim 5, characterized in that the temperature of the gas leaving the nozzle (2) corresponds to the temperature of the   glass with a viscosity in a range from 105 to 108 Pa.   7. Method according to claim 5 or 6, characterized in that the gas flow speed is greater than the air inlet speed