Abstract:
The apparatus is an assembly of cooling fins attached to pipes or heat pipes. The fins are formed into a corrugated configuration of troughs and peaks with large sections of the peaks removed to permit air flow along the depths of the troughs as well as along the lengths of the troughs. Holes are also formed into the fins to accept and grip a pipe or heat pipe. The preferred embodiment has holes surrounded by split collars formed into each fin, with the collars aligned to accept and grip the pipe.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to cooling fin structures, and more particularly to an assembly of cooling fins attached to a pipe or heat pipes and the method of attaching such fins.  
         BACKGROUND OF THE INVENTION  
         [0002]    Multiple fin assemblies are commonly used for transferring heat. This heat transfer is frequently between a liquid or vapor flowing in pipes that are in contact with the fins, and air flowing past the fins. Sometimes the fins are in contact with a second liquid rather than air. Perhaps the most common use of such a configuration is a simple household radiator in which hot water flows through a copper pipe that passes through a central hole located in individual aluminum fins. Here, the fins surround the pipe, with the pipe being bonded to the fins at edges that define the holes. The copper pipe heats the fins, which in turn transfer the heat into the air around the pipe by natural convection.  
           [0003]    In more sophisticated installations, it has also been common to use a similar structure to transfer heat from a heat pipe to surrounding air. Here too, the fins are attached to the heat pipe by passing the heat pipe through a hole in the fins. The attachment method is usually brazing, gluing, soldering, mechanical or hydraulic expansion, or welding of the fins to the heat pipe. Unfortunately, this prior art means of attaching fins to pipes is time consuming and expensive. It involves the bonding of each individual fin to the pipe, and regardless of the specific bonding material, the technique requires applying the solder, brazing material, or epoxy to each individual fin, or an additional manufacturing process step to expand the tube mechanically or hydraulicly.  
           [0004]    It would be very beneficial and economical to be able attach fins to a pipe or heat pipe without handling each fin separately and without the use of bonding materials which have to be discretely applied to the fin structure.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention provides a unified assembly of fins attached to a pipe or heat pipe without the use of any intermediate bonding material. Because all the fins are formed as a single free standing assembly, the attachment to the pipe or heat pipe is greatly simplified.  
           [0006]    In a preferred embodiment, fins are folded or corrugated to form a serpentine surface with alternating peaks and troughs. The troughs, as viewed from one side, form the peaks as viewed from the opposite side. However, unlike prior art folded assemblies of fins, the fins of the present invention have large sections along the lengths of their peaks removed. These cut out portions along the peaks of the corrugated fins can easily be punched out before the corrugations are formed, when the sheet is still flat, or can be removed after folding. Typically, these sections are removed from all but a small portion of the ends of the peaks, so that in the finished assembly it appears as if alternating sets of fins have been strapped together in a few separate locations. These remaining sections of the peaks hold the fins together to make a single assembly, and also assure that the fins will remain properly separated. This configuration yields fins which do not act like normal corrugated fins.  
           [0007]    In another embodiment of the invention, a fin assembly is provided comprising a sheet of metal folded so as to form a plurality of alternating peaks and troughs having a wall extending between each of the peaks and troughs. A central portion of each of the peaks is removed to form a through-opening that is bounded by spaced-apart straps of the sheet metal so as to permit air flow parallel to the troughs. Each of the walls defines a hole and at least two slits extending radially from the hole and through a portion of the wall so that when a pipe is inserted through the hole, a portion of the wall projects outwardly in the direction of movement of the pipe.  
           [0008]    Typical corrugated fins can only be used with continuous air flow along the troughs of the fins, meaning they can only be oriented in one direction to take advantage of natural or forced convection. For natural convection, the troughs and peaks must be oriented nearly vertically. However, the fins of the present invention are multi-directional. Since the portions of the peaks which remain to hold the fins together are relatively small compared to the sections removed from the peaks, convection can generate air flow in the direction along the depths of the troughs, and that convection has essentially the same cooling effect as it would have on independent fins of the same surface area. This makes fins of the present invention particularly suitable for the many installations in which natural convection or undirected forced air is the cooling mode.  
           [0009]    The fin assembly of the invention is also attached to pipes or heat pipes in a different way than conventional fins. The attachment structure of the present invention comprises a series of holes, one or more in each folded fin, with the holes in all the folded fins aligned so that pipes or heat pipes can be inserted through all the aligned holes. However, the attachment of the fins to the pipes or heat pipes uses no bonding material. Instead, each hole in a fin is formed with radiating slits which form clamping fingers which act as springs by storing elastic energy and thereby exerting a retaining force against the pipes. A concentric radial pattern may be preformed into the material separating the slits so as to provide preferred bend-lines in the material. In a preferred embodiment, the diameter of the pipes are sized so that the pipes are forced into the holes and cause the fingers to bend outward to form a collar. Such split collars can also be formed at the same time the hole is punched into the fin by drawing out the material on the edge of the hole. However, a simpler manufacturing process is provided when the collars are formed by the pipe itself as it is forced through holes with radial cuts extending out from the holes.  
           [0010]    From a manufacturing standpoint it is much easier to form the holes and radial cuts before the fins are folded, so that the holes are punched and the material removed from the future peaks on a simple flat sheet of material. It will be understood that if collars are to be formed in a flat sheet that is ultimately going to be folded into a fin assembly, adjacent collars in the flat sheet must point in opposite directions. That is, in a flat horizontal sheet one collar must protrude down from the sheet while the collars adjacent to it must protrude up. Thus, after the sheet is folded to form the parallel fins of the assembly, the collars will all be pointing in one direction, and therefore be arranged so as to accept a pipe that is pushed through the collars.  
           [0011]    The present invention thereby furnishes a more easily manufactured and assembled cooling fin assembly on a pipe or a heat pipe than has previously been available. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein:  
         [0013]    [0013]FIG. 1 is a perspective view of the preferred embodiment of a corrugated fin assembly formed in accordance with the invention, penetrated by and attached to a pipe;  
         [0014]    [0014]FIG. 2 is a layout view of a portion of a flat sheet used to form the fin assembly of the preferred embodiment of the invention; and  
         [0015]    [0015]FIG. 3 is a perspective view of a corrugated fin assembly formed in accordance with an alternative embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship.  
         [0017]    [0017]FIG. 1 is a perspective view of the preferred embodiment of corrugated fin structure  10  of the invention in which pipe  12  penetrates each fin  14  and is held in thermal contact with each fin by a split collar  16 . Fins  14  are formed by folding a flat sheet into the serpentine configuration shown for corrugated fin assembly  10 .  
         [0018]    Fin assembly  10  differs from conventional corrugated fin assemblies because central portions of peaks  18  of the corrugations are removed to form slots  20 . Although in FIG. 1 they are substantially hidden by fins  14 , slots similar to slots  20  are also removed from lower peaks  22  of fin assembly  10 .  
         [0019]    Slots  20  give fin assembly  10  the capability of developing natural convection air flow in any orientation because, unlike conventional corrugated fins, there is nothing to block the air flow in the direction of the depth of the troughs, indicated by arrows A and B. Thus, as long as fins  14  are in vertical or near vertical planes, heat transmitted to fins  14  from pipe  12  will generate natural convection, regardless of which parts of fins  14  are uppermost.  
         [0020]    Straps or end portions  24 , which are the portions of upper peaks  18  and lower peaks  22  which remain after slots  20  are formed, also serve a vital purpose. Straps  24  hold individual fins  14  together to form fin assembly  10  so that fin assembly  10  can be handled as a single unit. Furthermore, straps  24  maintain the fin to fin spacing originally designed into the assembly.  
         [0021]    [0021]FIG. 1 also depicts one of a plurality of split collars  16 , which are a preferred structure for holding fin assembly  10  onto pipe  12 . Split collars  16  are formed in each fin  14 , and are substantially coaxial to one another. Split collars  16  are pre-formed through the surface of each fin  14  as a central hole  32  and a cruciform slit  34 . In this way, when pipe  12  is forced through holes  32 , radiating cruciform slits  34  deform outwardly so as to create a plurality of gripping fingers  37 . A concentric radial pattern or plurality of preformed score lines or thinning of the material separating the slits in cruciform slit  34 , provide preferred bend-lines  38  in the material. Bend-lines  38  are positioned radially outwardly from central hole  32  so as to create a preferred and uniform bending point for the gripping fingers so that they are substantially the same length and therefore exert approximately the same gripping force on pipe  12 . As shown in FIG. 2, slots  20  are cut from sheet  30  before sheet  30  is folded to form corrugated fin assembly  10 . Also before the folding operation, co-linear holes  32  are formed in sheet  30 , and cruciform slits  34  are cut into sheet  30  so as to radiate from holes  32 . Slots  20 , holes  32 , and cruciform slits  34  are all located on sheet  30  so that after sheet  30  is folded, slots  20  will be at the peaks of the corrugations and collars  16  will all be aligned with one another (FIG. 1).  
         [0022]    Collars  16  are formed from holes  32  and slits  34 . Collars  16  can either be preformed into sheet  30  by drawing the collars before sheet  30  is folded or, with properly selected materials and dimensions, after folding. If formed after folding, a mandrel or pipe can be pushed through holes  32  to form collars  16  by deforming gripping fingers  37  outwardly, in the same direction as the movement of the mandrel or pipe. In either case, holes  32  are sized so that when pipe  12  is installed it will merely require being pushed through collars  16 . Preferably, when pushing pipe  12  through holes  32 , tooling is positioned in the troughs between adjacent fins (e.g., a comb-like fixture) to provide support for the fin during the insertion and movement of pipe  12  through the fin. Significantly, with pipe  12  installed, split collars  16 , via gripping fingers  37 , will retain enough elasticity to hold pipe  12  with sufficient contact force to provide adequate, thermally conductive contact.  
         [0023]    Referring to FIG. 3, an alternative fin structure  40  comprises a plurality of fins  14  comprising an open-ended slot  44  and an opening  46  defined through each fin. Open-ended slots  44  and openings  46  are preferably centrally located within each fin  14 , and are arranged in substantially aligned relationship to one another from fin to fin. In this way, plurality of open-ended slots  44  and openings  46  form a receptacle-passageway through fin structure  40 . Open-ended slots  44  are sized so as to be the same or somewhat larger than the outer diameter of a pipe  42 , and openings  46  are sized so as to be the same or somewhat narrower than the outer diameter of a pipe  42 . Thus, when pipe  42  is inserted into the receptacle-passageway formed by open-ended slots  44 , it is retained in fin structure  40  via a press fit in openings  46 . Alternatively, pipe  42  may be maintained within open-ended slots  44  be soldering, brazing, or thermal adhesives. Also, more than one pipe  42  may be positioned within open-ended slots  44 .  
         [0024]    Of course, open-ended slots  44  and openings  46  may have a variety of shapes, sizes and locations in fin structure  40 . For example, open-ended slots  44  may be defined by tapering edges of each fin  14 . Openings  46  may be defined by substantially circular, elliptical, polygonal or rectilinear edges of each fin  14 . The location within fins  14  of openings  46 , and the length, width, and orientation of open-ended slots  44  may also vary as required for a particular application without departing from the scope of the invention. Furthermore, fin structure  40  may comprise only open-ended slots  44 .  
         [0025]    The present invention provides a versatile cooling fin structure which is not restricted in its orientation for convection cooling, and which can easily be