Abstract:
An apparatus and method for drawing round stock to produce tubing includes a drawing machine including a drawing die, as well as an evaporative cooling mechanism adjacent to the drawing machine. The evaporative cooling mechanism defines a passageway in axial alignment with tubing drawn in a straight drawing direction and includes a nozzle for producing a fine fluid for cooling the tubing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. patent application Ser. No. 09,747,611 filed on Dec. 22, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a method and apparatus for drawing round stock to produce tubing and, more particularly, to a method and apparatus for cooling the drawn tubing between successive stages of drawing.  
         BACKGROUND OF THE INVENTION  
         [0003]    When drawing tubes to reduce the tube diameter and tube wall thickness, the tubes rapidly increase in temperature as they are forced through the die and about the mandrel. The increase in temperature causes the tubes to become brittle, often resulting in broken tubes. The problem becomes more serious as a larger diameter reduction is necessary because the stock tubing must be forced through a series of dies, each of which increases the temperature of the tubing. The loss of stock tubing and the production of low quality tubing is a significant disadvantage of the conventional manufacturing process.  
         SUMMARY OF THE INVENTION  
         [0004]    The method and apparatus according to the invention draws round stock to reduce the tube diameter and the tube wall thickness through a series of dies with evaporative cooling between each successive die. More particularly, a series of drawing machines are adjacently arranged in line such that round stock is successively drawn to form increasingly smaller tubing through each machine. Cooling between each machine is provided in an evaporative cooling mechanism connected to a source of fluid and having spray nozzles for applying a mist of fluid to the tubing as it moves from one drawing machine to the next. Through this process and apparatus, the drawn tubing is appropriately cooled to prevent breaking of the tubing as it is successively drawn.  
           [0005]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0007]    [0007]FIG. 1 illustrates schematically an arrangement of drawing machines with interposed cooling mechanisms;  
         [0008]    [0008]FIG. 2 is a flow diagram of the process according to the invention;  
         [0009]    [0009]FIG. 3 is a perspective view of an evaporative cooling mechanism according to the invention;  
         [0010]    [0010]FIG. 4 is an end view of the evaporative cooling mechanism of FIG. 3; and  
         [0011]    [0011]FIG. 5 is a cross-sectional view of a nozzle assembly used in the evaporative cooling mechanism of FIG. 3 and schematically illustrates communication with a source of cooling fluid. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0013]    [0013]FIG. 1 illustrates an apparatus  10  for drawing stock tubing with interposed cooling stages according to the invention. As shown, evaporative cooling is provided between adjacent drawing machines, whereby drawn tubing  12  is cooled between successive drawing stages. While three drawing machines  20 ,  22 ,  24  are shown, more or fewer drawing stages may be employed as required to narrow the diameter of the drawn round stock and thin the tubular walls thereof. Between each drawing machine is an evaporative cooling mechanism  26 , as shown. More or fewer evaporative cooling mechanisms  26  can be provided as needed for the drawing machines.  
         [0014]    The drawing machines can be any conventional drawing apparatus for drawing stock tubing to reduce the tubular diameter and wall thickness thereof through a plurality of drawing stages. Preferably, the drawing machines are those sold by Firma Schumag AG of Aachen, Federal Republic of Germany, such as that described in U.S. Pat. No. 4,962,658, which is herein incorporated by reference.  
         [0015]    The method according to the invention is illustrated in FIG. 2. At  50 , the process of drawing round stock with evaporative cooling begins. At  52 , stock tubing is provided for drawing into tubing have a narrower diameter and thinner walls. At  54 , the stock tubing is drawn through a first drawing machine. Before proceeding to the next drawing machine at  58 , the drawn tubing is cooled at  56  by an evaporative cooling mechanism. At  60 , if there are additional drawing machines for further reducing the drawn tubing&#39;s diameter, the process moves to  62 , where the drawn tubing is cooled by another evaporative cooling mechanism before returning to step  58 , where the once-drawn tubing is drawn through the next drawing machine to further reduce the diameter thereof. After the last drawing stage is completed, the process ends at  64 .  
         [0016]    The evaporative cooling mechanism  26  is illustrated in FIGS. 3 and 4. As shown, the evaporative cooling mechanism  26  generally includes a box-like housing  30  with a rectangularly cross-sectioned tubing passageway therethrough, and four nozzle assemblies  34 . More or fewer nozzle assemblies can be provided as needed. The housing  30  preferably includes six sides, including two generally rectangular sides  32  disposed adjacent each other, a pair of shorter generally square sides  36  separated from each other by the passageway, and two generally opposed sides  38  having a generally rectangular opening therein to provide an ingress and egress for tubing  12  traversing the passageway. Each side  32 ,  36 ,  38  of housing  30  includes a slot  70  for adjustably receiving a nozzle assembly  34 . Further, each nozzle assembly  34  is connected to a supply source of fluid. The fluid is preferably water.  
         [0017]    As the tubing  12  passes from one drawing machine to the next, it is cooled by the evaporative cooling mechanism  26 . More specifically, the tubing  12  passes through the passageway of evaporative cooling mechanism  26  where it receives a mist of water or other fluid from the nozzle assemblies  34 . The nozzle assemblies  34  are particularly adapted to apply a fine mist of water or other fluid, whereby the heat from the drawn tubing  12  rapidly evaporates the fluid. This rapid evaporation provides the necessary cooling between drawing stages, and provides clean, dry tubing  12  for the subsequent drawing machine.  
         [0018]    Each nozzle assembly  34  includes a base plate  72  and a nozzle  74 . Each base plate  72  and nozzle  74  are slidably received in the slot  70  of the sides  32 , 36  to adjustably mount the nozzle assembly  34  to the housing  30  for appropriate evaporative cooling of the tubing  12 . Fasteners  76  are provided to secure the nozzle assembly  34  in place once properly adjusted in each slot  60 .  
         [0019]    As shown in FIG. 5, each nozzle assembly  34  includes a cylindrical body  40 , a passageway  42  through the body  40 , and an inlet  44  and outlet  46  for the passageway  42 . At the inlet  44 , the nozzle  64  is connected to a source  41  of water or other fluid by an adaptor  45 . The passageway  42  contains a velocity tube  43  that receives the water or other fluid at the inlet  44  and transports it through the nozzle passageway  42 . The velocity tube  43  connects at the outlet  46  of the nozzle  64  to a chamber  47 . The diameter of the chamber  47  narrows toward the outlet  46  to such an extent that the fluid pressure is increased.  
         [0020]    A spray tip  48  is preferably connected to the chamber  47  by a push lock  49 , as shown in FIG. 5, or by some other known method of retention. The spray tip  48  releases the water in the form of a fine mist at the outlet  46 . The narrowly directed mist is aimed at the drawn tubing  12  passing through the evaporative cooling mechanism  26 .  
         [0021]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.