Abstract:
An apparatus and method of forming serpentine heat exchanger coils from spine fin tubing involves applying spine fins to a tube while simultaneously forming the tube into a serpentine shape. The bending and fin wrapping occurs while a feed roll continues paying out the tube without interruption. Multiple bends can be made simultaneously.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to heat exchanger coils having spine fin tubing. More particularly, the present invention relates to manufacturing such a heat exchanger.  
           [0003]    2. Description of Related Art  
           [0004]    Some heat exchangers or coils used for transferring heat from one fluid to another comprise a tube formed into a serpentine shape. Usually a refrigerant, or some other fluid, travels through the interior of the tube, while a second fluid, such as air, passes across the tube&#39;s exterior. To enhance heat transfer between the fluids, the tube may include fins or some other heat transfer member on the exterior of the tube. Often the fins are relatively thin and delicate, thus making it difficult to form the tube into a serpentine shape without damaging the fins. The fins of spine fin tubing, as disclosed in U. S. Pat. Nos. 3,005,253; 3,134,166; 3,160,129; and 3,688,375 (all of which are specifically incorporated by reference herein), are especially fragile and easily damaged.  
           [0005]    Currently, serpentine coils with spine fins are manufactured in multiple operations. First, the spine fins are applied to the tube by a machine known as a spine fin wrapper, as disclosed in U. S. Pat. Nos. 4,383,592 and 4,542,568. Later, the tube with the spine fins is transferred to a tube bender, which sequentially makes numerous individual bends until creating the desired serpentine shape.  
           [0006]    Typically, each bend is made individually at one general location on the tube bender, while the tube indexes across that general location. To do this, the feeding of the tube into the tube bender must pause momentarily with every bend, which results in a slow, interrupted process.  
           [0007]    Moreover, each bend of the tube shifts the completed portion of the coil (i.e., that which has already been formed into a serpentine shape) from one side to the other. This shifting movement can be tolerated if the coil is relatively small. With larger coils, however, attempting to shift the bulk and mass of the completed portion of the coil can damage the spine fins and inhibit the bending process.  
           [0008]    Consequently, a need exists for a production piece of equipment that can readily produce large serpentine coils from spine fin tubing.  
         SUMMARY OF THE INVENTION  
         [0009]    It is an object of the present invention to create serpentine coils without having to shift the entire coil back and forth with each bend of the coil.  
           [0010]    Another object of the invention to provide a multi-operational machine that can apply spine fins to a tube as well as form the tube into a serpentine shape.  
           [0011]    Another object is to apply spine fins to a tube while bending the tube at the same time.  
           [0012]    Yet another object of the invention is to provide a tube bender that can form serpentine coils of various widths.  
           [0013]    A further object of the invention is to form a serpentine coil without having to stop a tube feed roll with every bend of the tube.  
           [0014]    A still further object is to provide a tube bender that can simultaneously bend a tube at multiple points.  
           [0015]    Another object is to provide a method of creating tight, small radius bends by maintaining the tube in tension.  
           [0016]    These and other objects of the present invention, which will better be appreciated when the following description of the preferred embodiment and attached drawing figures are considered, are accomplished in a tube bender that applies spine fins to a tube while simultaneously forming the tube into a serpentine shape. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows a top view of a tube bender simultaneously wrapping spine fins around a tube and bending the tube according to one embodiment of the invention.  
         [0018]    [0018]FIG. 2 shows a top view of the tube bender of FIG. 1, but shown in another position.  
         [0019]    [0019]FIG. 3 is a view taken along line  3 - 3  of FIG. 2, but with the tube omitted to show other features of the invention more clearly.  
         [0020]    [0020]FIG. 4 is a cross-sectional view taken along line  4 - 4  of FIG. 7.  
         [0021]    [0021]FIG. 5 is a cross-sectional view taken along line  5 - 5  of FIG. 2.  
         [0022]    [0022]FIG. 6 is a cross-sectional view taken along line  6 - 6  of FIG. 2.  
         [0023]    [0023]FIG. 7 shows a top view of the tube bender of FIG. 1, but shown in another position.  
         [0024]    [0024]FIG. 8 shows a top view of the tube bender of FIG. 1, but shown in another position.  
         [0025]    [0025]FIG. 9 shows a top view of the tube bender of FIG. 1, but shown in yet another position.  
         [0026]    [0026]FIG. 10 shows a top view of the tube bender of FIG. 1, but with the tube bender adjusted to form a narrower serpentine coil.  
         [0027]    [0027]FIG. 11 is a view taken along line  11 - 11  of FIG. 10, but with the tube omitted to show other features of the invention more clearly. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    To create a serpentine coil  10  made of spine fin tubing  12 , a tube bender  14  includes a feed roll  16  that delivers a tube  18  through a spine fin wrapper  20  and a bending station  22 , as shown in FIG. 1.  
         [0029]    Spine fin wrapper  20  applies a heat conductive member, such as spine fins  24 , to the outer diameter of tube  18  to create spine fin tubing  12 . In some cases, tubing  12  starts out as  {fraction (3/8)}″ diameter aluminum tubing with aluminum spine fins increasing its overall final diameter to  1.5″; however, various other diameters and materials are well within the scope of the invention. Spine fins  24  are preferably applied to tube  18  by having a rotating head  26  helically wrap one or more ribbons  28  of spine fins  28  around tube  18 , as feed roller  16  pays out tube  18  through a central aperture of head  26 . A roller  30  can feed the ribbon of spine fins  24  to head  26 . Further details of spine fin wrapper  20  can be found in U. S. Pat. Nos. 4,381,592 and 4,542,568, which are specifically incorporated by reference herein.  
         [0030]    While spine fins  24  are applied to tubing  18 , station  22  bends tube  12  into the serpentine shape. To do this, station  22  includes a frame  32  with two rotating members  34  and  36 . As viewed in FIG. 1, member  34  rotates counterclockwise, while member  36  rotates clockwise. Upon the completion of each bend, the position of members  34  and  36  are about 90-degrees out of phase with each other. This allows dies  38   a,    38   b,    38   c  and  38   d,  which are mounted to members  34  and  36 , to sequentially engage tube  12  over bending region  22  of frame  32 , and thus bend tube  12  as members  34  and  36  rotate. For example, die  38   a  simultaneously bends tube  12  at points  40  and  42  as member  34  rotates from its position of FIG. 1 to that of FIG. 2.  
         [0031]    The actual structure of bending station  22  can vary widely. However, in one form of the invention, members  34  and  36  each comprise a structural channel  44  welded or otherwise fixed to a shaft  46  or  48 . Referring further to FIG. 3, bearings  50  allow members  34  and  36 , and their respective shafts  46  and  48 , to rotate relative to frame  32 . A drive motor  52  rotates shafts  46  and  48  by way of a drive train comprising sheaves or sprockets  54 ,  56 ,  58  and  60 ; belts or chains  62  and  64 ; and gears  66  and  68 . Sprockets  56  and  58  are fixed to shaft  48 , gear  68  is fixed to shaft  46 , and gear  66  and sprocket  60  are fixed to a shaft  70 . Bearings  72  allow shaft  70 , gear  66  and sprocket  60  to rotate relative to frame  32 . Gears  66  and  68  mesh to rotate members  34  and  36  in opposite directions.  
         [0032]    Dies  38   a - d  each has a retractable protrusion  74  that slides vertically within a C-shaped bracket  76 , which in turn is bolted to channel  44 , as shown in FIGS. 3 and 4. A shoulder  78  fixed relative to protrusion  74  allows a compression spring  80  acting between shoulder  78  and a lower flange of bracket  76  to urge protrusion  74  to a retracted position, as shown in FIG. 4. However, when die  38   a  is underneath an upper plate  82 , a cam surface  84  of plate  82  applies a downward force against a roller  86 , which moves protrusion  74  to an operative position of FIG. 5. In the operative position, protrusion  74  is able to engage and thus bend tube  12  as member  34  moves protrusion  74  across bending region  22 . Once a particular bend has been completed, member  34  moves die  38   a  out from underneath surface  84 . This allows spring  80  to push protrusion  74  back up to its retracted position where protrusion  74  disengages tube  12 , as shown in FIG. 4. Referring to FIG. 3, an inclined portion  88  of cam surface  84  provides roller  86  with a gradual lead-in for moving protrusion  74  from its retracted position to its operative position.  
         [0033]    To temporarily hold point  42  generally fixed while member  34  bends tube  12  at points  40  and  42 , a retractable anchor  90  is mounted to frame  32  in the general vicinity of point  42 . For member  36 , a similar anchor  92  is disposed at another point  100  complementary to point  42 . In some forms of the invention, anchors  90  and  92  each comprise an air cylinder  94  that extends and retracts between a release position of FIG. 5 and an extended position of FIGS. 4 and 6.  
         [0034]    In operation, feed roll  16  unwraps tube  18  to create an unwrapped section of tube  15  extending from a point  96  to point  42 , with point  40  being at an intermediate position between points  42  and  96 . Fin wrapper  20  wraps spine fins  24  around tube  15  at a location between points  96  and  40 . Upon leaving fin wrapper  20 , tube  15  passes across a tube-receiving end  98  of frame  32  and extends over bending region  22 . With tube  15  and bender  14  in the position of FIG. 1, anchor  90  extends (see FIG. 6) to help hold tube  12  at point  42 , while member  34  pushes protrusion  74  of die  38   a  against tube  12  at point  40 . Tube bender  14  moving from the position of FIG. 1 to that of FIGS.  2  completes the bend at point  42  and, at the same time, partially bends tube  12  at point  40 .  
         [0035]    The relative rotational speed of member  34  and feed roll  16  helps maintain tube  15  in tension, which helps keep tube  12  generally straight between points  40  and  42 . In some embodiments of the invention, feed roll  16  has a certain amount of rotational drag that creates tension in tube  15  as members  34  and  36  pull tube  15  from feed roll  16 . In other embodiments, feed roll  16  is driven at a generally constant speed, while drive  52  (FIG. 3) is a hydraulic motor supplied with hydraulic fluid at a constant pressure. This results in a constant rotational torque being applied to members  34  and  36 , thereby limiting the tension in tube  15 .  
         [0036]    As members  34  and  36  continue rotating from the position of FIG. 2 to that of FIG. 7, member  34  moves die  38   a  out from underneath cam surface  84 . This allows spring  80  to push protrusion  74  back up to its retracted position where protrusion  74  disengages tube  12 , as shown in FIG. 4. Also, in preparation for completing the bend at point  100  as well as initiating the next bend, member  36  moves die  38   b  along inclined portion  88  of cam surface  84  (see FIG. 3) to extend protrusion  74  to its operative position. In addition, anchor  92  retracts to its release position of FIG. 5, and anchor  90  extends to its extended position of FIG. 6. Conventional fluid control valves can actuate anchors  90  and  92  at the precise time in response to conventional limit switches that sense the position of member  34  or  36 .  
         [0037]    Next, members  34  and  36  move from their positions of FIG. 7 to that of FIG. 8. FIG. 8 is similar to FIG. 1; however, member  34  and die  38   a  do the bending in FIG. 1, while in FIG. 8, member  36  and die  38   b  do the bending. Thus, in FIG. 8, die  38   b  is in its operative position, anchor  92  is in its extended position, and anchor  90  is in its release position. Also, die  38   a  being out from underneath upper plate  82  is in its retracted position. This allows die  38   a  to pass over the completed serpentine portion  10  of tube  12  that is resting upon a support structure  102  of frame  32 .  
         [0038]    From the positions of FIG. 8, members  34  and  36  rotate to the positions shown in FIG. 9. FIG. 9 is similar to FIG. 2; however, die  38   b  of member  36 , rather than die  38   a  of member  34 , has just completed a bend. As members  34  and  36  continue rotating, die  38   c  is next to bend tube  12 , followed by die  38   d,  and then die  38   a  comes around again to make yet another bend, which begins another cycle. As the repeating cycles continue, the serpentine portion  10  of the coil grows to the right, as viewed in FIG. 9, until the coil is cut to a desired length and removed from support structure  102 . From there, the serpentine coil can be made into a complete heat exchanger, which may include framework, manifolds, inlet and outlet ports, etc. The coil may also be formed further into a shape other than just flat.  
         [0039]    Although, coil  10  has a specific width  104 , tube bender  14  can be adjusted to make a serpentine coil  10 ′ having a narrower width  106 , as shown in FIG. 10. To do this, dies  38   a - d  can be moved closer to their corresponding shaft  46  or  48 . In FIG. 11, for example, bracket  76  of die  38   a  is unbolted from mounting holes  108  of member  34  and reinstalled closer to shaft  46 . Anchors  90  and  92  are also moved closer to each other in a similar unbolting/bolting manner. Of course, there are a wide variety of other common methods of repositioning tooling such as having a lead screw move the dies and anchors along guide tracks.  
         [0040]    Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that other variations are well within the scope of the invention. For example, to minimize the bending of tube  15  just as it leaves head  26 , spine fin wrapper  20  can be installed much farther away from tube-receiving end  98  than -what is shown in the drawing figures. Also, guides can be added to help guide tube  15  as tube  15  travels from head  26  to tube-receiving end  98 . Therefore, the scope of the invention is to be determined by reference to the claims, which follow.