Tube reduction apparatus with integral means for sensing wall thickness during a high speed tube drawing operation

• US 4,196,607 A
• Filed: 04/03/1978
• Issued: 04/08/1980
• Est. Priority Date: 04/03/1978
• Status: Expired due to Term

• Current Assignee: Wolverine Tube Incorporated
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Youtsey, Karl J., Tatum, John M.
• Primary Examiner(s): Mehr, Milton S.
• Application Number:
  US05/892,588
• Time in Patent Office: 736 Days
• Field of Search: 72/283, 72/274, 72/253, 72/264, 72/9, 72/10, 72/34, 73/622, 73/625, 73/628, 73/641, 29/407
• US Class Current: 72/31.06
• CPC Class Codes: B21C 1/24 by means of mandrels
• CPC Class Codes: B21C 3/12 Die holders; Rotating dies
• CPC Class Codes: B21C 51/00 Measuring, gauging, indicating, counting, or marking devices specially adapted for use in the production or manipulation of material in accordance with subclasses B21B - B21F
• CPC Class Codes: G01B 17/02 for measuring thickness

Abstract

An improved drawing die apparatus is disclosed for reducing the wall thickness of a thin wall metal tube in cooperation with a floating pin or a fixed mandrel. At least three, and preferably four, wall thickness sensors are positioned in the die body in angular relationship around the outer periphery of a carbide draw die nib for indicating the wall thickness, and thus the eccentricity, of the tubing as it is being produced. Preferably, the sensors are contact type ultrasonic transducers which are acoustically coupled with a viscous couplant to flats formed on the draw nib in regions overlying a land region of the die. The acoustic coupling between the draw nib and tube is achieved through the O.D. drawing lubricant.

Claims

1. A tube reduction apparatus for continuously sensing the wall thickness of a tube at various locations around its periphery as it is being reduced in diameter and wall thickness at normal drawing speeds comprising a drawing die assembly including a die body having a die nib member rigidly locked therein, said die nib member having a cylindrical, internal, axially positioned land portion which defines its minimum internal diameter and a generally conical lead-in portion, the internal walls of which smoothly blend into the internal wall defined by the land portion, said lead-in portion and said land portion being adapted to cooperate with both a lubricant coated tube to be drawn which has an outer diameter greater than that of the land portion and with a mandrel located inside the tube to reduce the outer diameter of the tube to a dimension approximately equal to the internal diameter of the land portion, tube wall thickness sensing means including at least three sensing elements located in said die body at angularly spaced positions around the outer circumference of said die nib member in radial alignment with said land portion but spaced therefrom, said sensing elements each being adapted to produce signals representative of the instantaneous wall thickness of the portion of the tube passing inwardly of them, said sensing elements being at all times physically isolated from the tube and lubricant and thus protected from damage by the tube or from contaminating particles in said lubricant.

2. The apparatus of claim 1 wherein said sensing elements comprise ultrasonic transducers.

3. The apparatus of claim 1 wherein said tube wall thickness sensing means comprises four sensing elements.

4. The apparatus of claim 3 wherein said four sensing elements are positioned in two opposed pairs.

5. The apparatus of claim 2 wherein said ultrasonic transducers are of the direct contact type and are mounted in said die body in contact with the outer peripheral surface of said die nib member.

6. The apparatus of claim 5 wherein said die nib member has flat areas formed on its outer surface which are in parallel contacting relation with crystals in said transducers.

7. The apparatus of claim 6 wherein said transducers are threadedly mounted in said die body with sufficient looseness in the threads to permit the transducer body to be moved slightly in a gimbal fashion as the flat crystal end portion thereof is moved into parallel engaging contact with a flat area on said die nib member.

8. The apparatus of claim 5 wherein said die nib member is made of an acoustically attenuative material such as tungsten carbide and said transducers have a flat crystal end portion which is coated with a first outer coating of electrode material and with a second outer coating of a viscous acoustic couplant to provide a grounded contact with said die nib member.

9. The apparatus of claim 8 wherein said electrode material comprises a layer of conductive silver paint and said acoustic couplant is a jelly-like substance.

10. The apparatus of claim 9 wherein said first coating is approximately 1 mil thick and said second coating is approximately 10 mils thick.

11. The apparatus of claim 1 wherein the signals from said sensing elements are transmitted to a plurality of wall thickness gages, the output of which is transmitted to one or more recording devices which may record the sensed wall thickness.

12. The apparatus of claim 11 wherein the signals from said wall thickness gages are first transmitted to an analog-digital convertor then to a digital computer, and simultaneously to a strip chart recorder which displays a continuous trace of the thickness of the wall underneath one or more sensors.

13. The apparatus of claim 12 wherein the signals from said digital computer are also transmitted to a data recording system which provides a permanent record of the wall thickness of the tube being drawn at spaced points along its length and at spaced locations around its periphery.