# US 2017/0254733 A1 · Apparatus and method for preform or tube drawing based on its viscosity > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0254733 A1 - Document ID: US20170254733A1 - Status: Published application - Kind: A1 - Application number: 15/517,045 - Filed: 2014-10-14 - Published: 2017-09-07 - Earliest claimed: 2014-10-14 - Assignees: Heraeus Tenevo GmbH - Applicants: Heraeus Tenevo LLC - Inventors: Georges Levon FATTAL; James E. BEAVERS, Jr.; Kai Huei CHANG; Evan P. GREEN; Qiulin MA - Web page: https://patentgrep.com/patent/US20170254733A1 ## CPC - G01N 11/06: by timing the outflow of a known quantity - C03B 23/047: by drawing ({C03B23/091} , C03B37/025 takes precedence) - C03B 37/01242: {Controlling or regulating the down-draw process} - G01N 11/00: Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties - G01N 11/02: by measuring flow of the material - G01N 11/08: by measuring pressure required to produce a known flow - C03B 23/0473: {for forming constrictions} - C03B 37/0124: {Means for reducing the diameter of rods or tubes by drawing, e.g. for preform draw-down} - C03B 2205/40: Monitoring or regulating the draw tension or draw rate - G01N 11/04: through a restricted passage, e.g. tube, aperture - G01N 2011/006: {Determining flow properties indirectly by measuring other parameters of the system} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES ## Abstract Methods for preform and tube draw based on controlling forming zone viscosity determined by calculating a holding force exerted by the glass component in the forming zone on the strand being drawn below. The holding force may be calculated by determining a gravitational force applied to the strand and a pulling force applied to the strand by a pulling device, where the holding force is equal to the opposite of the algebraic sum of the gravitational and pulling forces. The holding force may also be calculated by measuring a stress-induced birefringence in the strand at a point between the forming zone and the pulling device, determining an amount of force applied to the strand at the point corresponding to the birefringence, and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the forming zone and the point. ## Claims ### Claim 1 A method of measuring the viscosity of a forming region of a glass preform or tubing fabrication process, wherein the fabrication process comprises heating a bulk glass component in a heating region, drawing a strand from the forming region of the bulk glass component, and using a pulling device to control the rate at which the strand is drawn, the method comprising: calculating a holding force applied to the strand by the forming region, and correlating the holding force with the viscosity of the forming region. ### Claim 2 (depends on 1) The method of claim 1, wherein the holding force is used to control the glass preform or tubing fabrication process by adjusting the heating of the bulk glass component based on the holding force. ### Claim 3 (depends on 1) The method of claim 1, wherein calculating the holding force comprises: determining a gravitational force applied to the strand; and determining a pulling force applied to the strand by the pulling device, wherein the sum of the holding force, the gravitational force, and the pulling force equals zero. ### Claim 4 (depends on 3) The method of claim 3, wherein determining the gravitational force comprises determining a length of the strand and calculating the mass of the strand. ### Claim 5 (depends on 3) The method of claim 3, wherein determining the pulling force applied to the strand by the pulling device comprises: measuring a voltage applied to the pulling device; measuring a torque applied by the pulling device to the strand; and calculating the pulling force from the voltage and the torque. ### Claim 6 (depends on 3) The method of claim 3, wherein determining the pulling force applied to the strand by the pulling device comprises measuring the output of load cells applied to the pulling device. ### Claim 7 (depends on 1) The method of claim 1, wherein the pulling device includes a gripping device that clamps onto the strand and moves vertically. ### Claim 8 (depends on 1) The method of claim 1, wherein calculating the holding force comprises: measuring a stress-induced birefringence in the strand at a point at or below the heating region; determining an amount of force applied to the strand at the point which corresponds to the measured stress-induced birefringence; and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the heating region and the point, wherein the correction is zero if the point is at the forming zone. ### Claim 9 (depends on 8) The method of claim 8, wherein measuring the stress-induced birefringence in the strand comprises: positioning the strand between a sensor and a polarized light source; emitting a polarized light from the polarized light source onto the strand; and measuring the degree of transmission of the polarized light through the strand by the sensor. ### Claim 10 (depends on 8) The method of claim 8, wherein the strand is at approximately an annealing temperature of the glass strand at the point. ### Claim 11 A method of producing an elongated component of glass, said method comprising heating a bulk glass component in a heating region at a temperature; drawing a strand from the bulk glass component at a forming region of the bulk glass component; using a pulling device to control the rate at which the strand is drawn from the bulk glass component; calculating a holding force applied to the strand by the forming region; determining whether the holding force is equal to a desired holding force based on a desired viscosity of the forming region; and adjusting the temperature of the heating region if the holding force is not equal to the desired holding force. ### Claim 12 (depends on 11) The method of claim 11, wherein calculating the holding force comprises: determining a gravitational force applied to the strand by determining a length of the strand and calculating the mass of the strand; and determining a pulling force applied to the strand by the pulling device, wherein the sum of the holding force, the gravitational force, and the pulling force equals zero. ### Claim 13 (depends on 12) The method of claim 12, wherein determining the pulling force applied to the strand by the pulling device comprises: measuring a voltage applied to the pulling device; measuring a torque applied by the pulling device to the strand; calculating the pulling force from the voltage and the torque. ### Claim 14 (depends on 12) The method of claim 12, wherein determining the pulling force applied to the strand by the pulling device comprises measuring the output of load cells applied to the pulling device. ### Claim 15 (depends on 11) The method of claim 11, wherein the pulling device includes a gripping device that clamps onto the strand and moves vertically. ### Claim 16 (depends on 11) The method of claim 11, wherein calculating the holding force comprises: measuring a stress-induced birefringence in the strand at a point at or below the heating region; determining an amount of force applied to the strand at the point which corresponds to the measured stress-induced birefringence; and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the heating region and the point, wherein the correction is zero if the point is at the forming zone. ### Claim 17 (depends on 16) The method of claim 16, wherein measuring the stress-induced birefringence in the strand comprises: positioning the strand between a sensor and a polarized light source; emitting a polarized light from the polarized light source onto the strand; and measuring the degree of transmission of the polarized light through the strand by the sensor. ### Claim 18 An apparatus for measuring the viscosity of a forming region of a glass preform or tubing fabrication process, wherein the fabrication process comprises heating a bulk glass component, drawing a strand from the bulk glass component, and using a pulling device to control the rate at which the strand is drawn, the system comprising: a heating zone for heating the bulk glass component, wherein the forming region is at or immediately below the heating zone; a system for determining the force applied to the strand by the pulling device; and a system for determining the weight of the strand based on the weight and the length of the strand. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein the system for determining the force applied to the strand by the pulling device comprises a voltage meter for measuring the voltage applied to a motor of the pulling device, wherein the voltage can be correlated with the force applied to the strand by the pulling device. ### Claim 20 (depends on 18) The apparatus of claim 18, wherein the system for determining the force applied to the strand by the pulling device comprises one or more load cells mounted to the pulling device. ### Claim 21 (depends on 18) The apparatus of claim 18, wherein the pulling device includes a gripping device that clamps onto the strand and moves vertically. ### Claim 22 (depends on 18) The apparatus of claim 18, wherein the system for determining the weight of the strand comprises a camera vision system, a laser system, or a mechanical device to determine the vertical position of the end of the strand. ### Claim 23 (depends on 18) The apparatus of claim 18, wherein the system for determining the weight of the strand comprises a system for measuring the velocity of the strand and determining the length of the strand based on the velocity of the strand.