Heraeus Quarzglas Gmbh & Co Kg

Fraunhofer-gesellschaft Zur Foerderung Der Angewandten Forschung E.v.

Heraeus Quarzglas Gmbh

Heraeus Tenevo Gmbh

Thomas Bogdahn

Oliver Ganz

Harald Hain

Ralph Sattmann

Oliver Humbach

Thomas Bernard

Eric Emmert

Frank G&auml;nsicke

Markoto Sajidman

A method for using a temperature control loop in order to further develop process control during elongation of a cylindrical preform such that a component strand with high dimensional accuracy can be drawn even in the presence of temperature-effective defects during the elongation process: (a) the continuous measurement of a first temperature value, T, at an upper measuring point on the surface of the cylindrical preform; (b) the continuous measurement of a second temperature value, T, at a lower measuring point; (c) calculation of a temperature distribution in the region between the measuring points Tand T, and determination of a modelled deformation temperature, T, using an algorithmic model taking with first and the second temperature values as model input parameters, and the modelled deformation temperature, T, as a regulating variable and the heating-zone temperature Tas a manipulated variable for the temperature-control loop.

Process for producing a cylindrical component made of glass by elongation

The present invention refers to a drawing method for producing cylindrical components of quartz glass in that a quartz glass strand is drawn off in the direction of a drawing axis from a shaping zone of soft quartz glass mass and sections having a cutting length are separated from the quartz glass strand, and the cylindrical components are produced from the sections.

Drawing method for producing cylindrical-shaped components from quartz glass

In a known method for producing a tube of quartz glass by elongating a hollow cylinder of quartz glass having an outer diameter AD, said cylinder is continuously supplied to a heating zone with a vertically oriented heating tube having an inner diameter d, with the proviso that the diameter ratio d/AD is set to a value ranging from 1.02 to 1.7. The hollow cylinder is softened therein zonewise, and a tubular strand is drawn off from the softened region and shortened to obtain the tube. Starting therefrom, in order to optimize the dimensional stability of the quartz glass tube obtained, it is suggested according to the invention that the heating zone should have a length L which is set such that the ratio L/d is smaller than 0.9.

Method for producing a tube of quartz glass by elongating a hollow cylinder of quartz glass

According to a known vertical drawing method for producing a cylindrical glass body, the cylinder longitudinal axis of the glass cylinder is adjusted by hand in relation to the longitudinal axis of a heating tube. The aim of the invention is to optimize the stability of said glass body. Said aim is achieved, whereby adjustment comprises the steps of detecting a value for a first radial x-y position of the cylinder longitudinal axis () of the glass cylinder () in a first horizontal detection plane (E), drawing the glass cylinder (), placed in the first x-y position, to form a test glass strand (), measuring an actual state of a radial circular, or annular dimension of the test glass strand, determining a deviation between the actual state and a set state of said circular, or annular dimension with regard to the size and position thereof, while considering the position of the glass cylinder () in relation to the inner wall of the heating tube () during drawing, calculating a corrected x-y position of the cylinder longitudinal axis () by means of a correction factor (K), the value and position of the deviation, arranging the glass cylinder () into the heating tube (), so that the cylinder longitudinal axis () extends at least in the first horizontal detection plane (E) in the x-y position and drawing the glass cylinder (), arranged in the corrected x-y position, to form another test glass strand ().

Vertical drawing method for producing a cylindrical glass body and device for carrying out said method

In a known method for producing a cylindrical glass body in a vertical drawing process, a glass blank is softened in a heating zone and drawn off as a glass strand by means of a draw-off device at a controlled drawing speed, the draw-off device comprising a first draw-off unit with rolling bodies rolling on the glass strand and being distributed around the circumference thereof, the rolling bodies being formed by a reference rolling body and at least one auxiliary rolling body, the drawing speed being controlled via the speed of the reference rolling body. Starting therefrom, in order to reduce damage to the surface of the glass strand caused by the draw-off device and to avoid deformations caused by existing bends of the glass strand, it is suggested according to the invention that a value for the torque of the reference rolling body () should be determined in dependence upon the weight of the drawn-off glass strand (), and that the determined value should be used as a setpoint torque for setting the torque in the at least one auxiliary rolling body ().

Method and device for producing a cylindrical glass body

A resistance furnace has a tubular heating element with a vertically-oriented longitudinal axis. The heating element has a shell surface defined by an upper side and a lower side and surrounding a furnace chamber. The heating element is connected to at least two supply terminals by which heating current is introduced at power supply points into the heating element. The supply terminals include a surrounding upper annular collar adjacent the upper side of the shell surface, and also a surrounding lower annular collar adjacent the lower side of the shell surface.

Resistance furnace with tubular heating element

In a known method for the manufacture of a tube made of a vitreous material, especially of quartz glass, a hollow cylindrical semifinished product made of a vitreous material is carried essentially vertically to a heating zone, wherein it is heated and drawn off downwards&mdash;without the use of tools&mdash;to the tube by forming a transitional area from semifinished product to tube, while diameter and wall thickness of the tube are continuously measured, and the tube's measured geometrical data being used to generate a control signal with the aid of which a pressure difference is regulated between pressure P in the interior space of the semifinished product, the transitional area and the tube, as well as pressure P in the heating chamber which is regulated in the heating zone at least in the transitional area from semifinished product to tube and its adjacent tube area. This method is to be developed further so as to enable the processing of a broader spectrum of hollow cylindrical semifinished products to tubes with the desired inside and outside dimensions. This task is solved according to the invention such that for the manufacture of tubes with the ratio of their outside diameter (D ) to their inside diameter (D ) being greater than the ratio of the outside diameter (D ) to the inside diameter (D ) of the semifinished product&mdash;pressure P in the inside space of the semifinished product, the transitional area and the tube being kept at a value which is smaller than the value of pressure P in the heating chamber, with pressure P being maintained by means of a suction (vacuum) pump.

Method for producing a tube made of quartz glass using low internal pressure and control of diameters

A glass blank is sent to a heating zone where it is softened region by region and drawn continuously in a controlled manner as a drawing bulb is formed. Estimates of at least one controlled variable are predicted free of dead time; in addition, at least one geometric variable of the component which can be correlated with the controlled variable is measured continuously, and the measurement values thus obtained are used to adjust the predicted estimates. On the basis of the predicted estimates thus adjusted, the nominal-actual deviation of the controlled variable is determined and converted to a change in a controlling variable. To ensure the production of a component with especially high dimensional accuracy, a geometric variable is measured at a first measurement site in the area of the drawing bulb for the prediction of the estimate, and the temperature of the drawing bulb be measured and used as a controlled variable. A measuring device to which a measurement site in the softened area of the blank is assigned is preferably provided to detect the geometric variable of the component.

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Karlstein, Germany

Thomas Bogdahn