Abstract:
This invention relates to fabrication of tube bank style heat exchangers and similar assemblies. It provides a novel device and a method for presenting and feeding multiple relatively flexible tubes in a predetermined spaced apart manner, and subsequently threading them through corresponding holes in tube-sheets, baffles or similar components during fabrication of the core structure, for example a heat exchanger core.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/376,621, filed Apr. 30, 2002 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to devices used to align tubes within manufactured structures. More particularly this invention relates to such devices used to present flexible tubes for insertion within structures such as heat exchanger cores and in which the tubes must be precisely positioned relative to each other.  
         BACKGROUND OF THE INVENTION  
         [0003]    A variety of manufactured components contain tubing arranged in configurations suitable for their particular uses. For example, tubes are arranged and secured within harnesses or otherwise clamped together in desired arrangements for the transport of fluid (including both liquids and gases). Several illustrations of such configurations are found in vehicles, where power steering fluids and coolants and the like are delivered through tubing and hoses that must be precisely located and secured within the engine compartment. In these cases, the installation of the tubing is relatively straightforward and not particularly time-consuming.  
           [0004]    However there are a multitude of more complex applications in which the article of manufacture contains a large number of tubes each of which must be precisely located relative to the other. One such example is in a tube bank-style heat exchanger, in which individual tubes need to be presented to tube sheets, baffles and other components and precisely fed through corresponding holes in them. Conventional approaches to the manufacture of such devices, and particularly those incorporating polymeric tubes that due to their flexibility pose significant challenges in precisely aligning them to holes and channels through which they must pass, include manual assembly. It will be readily appreciated that this is very laborious and time consuming. And while automated techniques have been developed to handle, position and feed rigid tubes (such as metal tubes) into appropriate receptacles, these approaches are generally not suitable for the manipulation of flexible tubes in assemblies because their orientation is less predictable.  
           [0005]    Compounding the problem, and again in tube bank-style heat exchangers using polymeric tubing, there are precise tolerances involved in positioning large numbers of small, flexible tubes within both a specific configuration and a compact design envelope. For example and depending on the application selected, tubes only 2 mm in diameter (or less) but having lengths of 2-3 feet (or more) might be arranged in a series of rows such that they are a mere 1-2 mm apart. In order to automate the process of feeding multiple tubes into a fixed receptacle, it is necessary not only to align the tubes (for example in a column) but also ultimately to position them in a pre-determined and spaced-apart manner.  
           [0006]    It is therefore an object of the present invention to provide a device suitable for the incorporation of a plurality of flexible tubes into a core assembly, and in which the tubes are aligned sufficient for insertion within the assembly in a desired configuration. Another object of the invention is to provide for such a device in conjunction with supporting apparatus to ensure that the tubes are pushed into the core assembly in a controlled manner and properly guided into position within the core assembly. A feature of the present invention is that it can accommodate a number of tube structure designs. Another feature is that the device can be made from a wide variety of materials, so long as the material selected is sufficiently rigid to guide the polymeric tubing along its surface without causing damage thereto. The invention offers several advantages, among them an automated process for the installation of flexible tubing into a core assembly such as a heat exchanger. These and other objects, features and advantages will become apparent upon having reference to the detailed description of the invention herein.  
         SUMMARY OF THE INVENTION  
         [0007]    There is provided and claimed herein a device for positioning flexible tubes at predetermined locations. This device comprises a surface comprising a channel formed therein. This channel is sufficient to accommodate a plurality of tubes arranged substantially proximally to one another along their lengths thereof. The channel also comprises a plurality of tapered surfaces interspersed within the channel to direct the tubes into passages therealong. The passages define a predetermined pitch of the tubes relative to each other. The surface is formed sufficient to contain the tubes within the device. Optionally a second surface is placed in contact with this surface so that together the surfaces are sufficient to contain the tubes.  
           [0008]    Further, the positioning device can be incorporated into an apparatus for the manufacture of core assemblies, like heat exchangers. In one configuration of such apparatus, a moveable ram urges the tubes contained in a receptacle (such as a cartridge) into the channel of the positioning device. Conduits are inserted into the passages of the positioning device, and guide the movement of the tubes therethrough. The conduits in turn are aligned with the core assembly so that the tubes are received and installed within this assembly. A guide mandrel is also used in conjunction with the device. It functions to draw the tubes into the core assembly without having them bend under their own weight, so that the tubes draw through various supporting structures.  
           [0009]    The invention will become better understood through a review of the following drawings that provide illustrations of various embodiments thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is an exploded view of the positioning means of the present invention and adapted to receive and to position the tubing as it moves therealong;  
         [0011]    [0011]FIG. 2 is a perspective view of an assembly of the present invention and including the positioning means in operation with additional apparatus to provide an automated process for the feeding of flexible tubing into a core structure;  
         [0012]    [0012]FIG. 3 is a side view of several embodiments of the positioning means of the present invention including configurations for passages; and  
         [0013]    [0013]FIG. 4 is a side view of two embodiments of the ram of the present invention and including staggered surfaces that contact the tubes. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    Having reference to FIG. 1, the positioning device is shown generally at  10 . It is seen that this device has a surface  12  and the various attributes of the device are machined onto this surface. Tubes are collected and gathered for presentation to the channel  14  formed on surface  12 . The tubes may be fashioned into any of a number of shapes in cross section as may be desired for a particular assembly, and it is even possible to present tubes of more than one shaping to the channel  14  at the same time. The tubes have a line of symmetry in cross section (for example as can be drawn in oval or circular or rectangular shapes), so that once identically shaped tubes are presented to the channel  14  they are identically aligned to said channel  14 . One popular shaping is the round tube.  
         [0015]    The channel  14  is of sufficient width to accommodate a collection of tubes arranged adjacent to one another and contacting the channel  14 . Thereafter and as the tubes are urged along the channel  14  (and substantially perpendicular to edge  15  thereof) they encounter a series of tapered surfaces  16 . These tapered surfaces  16  formed along the surface  12  are designed to gradually position the tubes into separate and defined passages  18 . They may be aligned linearly or staggered or in general located in any other configuration intended to direct the tubes toward the passages  18 .  
         [0016]    The passages  18  (just beyond the tapered surfaces  16 ) are of a suitable depth and width to accommodate the tubes and direct them along their designed pathway. For example, and without intending to limit the generality of the foregoing, the passages  18  illustrated in FIG. 1 are generally curved (except for the center passage  18  which is straight) and with the result that the tubes upon exiting the passages  18  of the positioning device  10  are spaced a predetermined distance apart from each other (known as “pitch”). It is readily appreciated that by varying the location of the tapered surfaces  16  and the passages  18  different technical effects can be achieved. For example, the designer might engineer the same or a different pitch between the tubes.  
         [0017]    The passages  18  also may contain etched portions  20  that are designed to receive conduits (not shown). The specifications and function of the conduits are described together with FIG. 2 further below.  
         [0018]    The passages  18  of the surface  12  may be machined to a size and geometry sufficient to contain the tubes therein. These passages  18  may be any of a number of shapings in cross section, several of which are illustrated in FIG. 3 (circular, diamond, and oval shaped). Moreover these passages  18  do not necessarily need to be shaped identically to the shape of the tube. For example, a passage  18  that is oval in cross section may nevertheless accommodate and direct a circular tube. A second surface  22  may contact the surface  12 , and functions to further secure the tubes within the channels and passages of the surface  12 . This second surface  22  is important for designs in which the surface  12  accommodates but does not securely contain the tubes (for example, if the passages  18  in the surface  12  are exposed at the surface  12  in a way that the tubes are not secured within them). In one embodiment, the second surface  22  is an exact duplicate of the surface  12  (and with each passage  18  alone shaped as a semi-circle), so that when the surfaces are joined the combined passages  18  are circular to allow a controlled movement of the tubes. Other embodiments are also contemplated, for example it is possible for the second surface  22  to be planar so long as the first surface  12  has a channel  14  and passages  18  formed therein of sufficient depth to allow for movement of the tubes.  
         [0019]    The positioning device  10  is held together by any of a variety of conventional means, including clamping or a pressed assembly or (as shown in FIG. 1) bolting of surfaces into place using bolts  21  which attach within another surface (such as the second surface  22 ).  
         [0020]    Having reference to FIG. 2, the positioning device  10  is shown as part of a larger apparatus generally designated at  30 . A ram  32  is applied to a stack of tubes. Generally the stack of tubes may be assembled in any suitable receptacle (as shown, they are stacked into columns  35  of cartridge  34 ). The force of the ram  32  urges the tubes through the positioning device  10  (at channel  14 ). The passages  18  of the positioning device  10  receive the conduits  36 . The ends of the passages  18  are oversized relative to other portions thereof, and the conduits  36  penetrate these passages  18  in the oversized area. In this manner the tubes traversing the passages  18  are not impeded as they pass through the region where the passages  18  join the conduits  36 .  
         [0021]    It is further seen that the tubes pass through the conduits  36  and to be received within the core assembly  38  (which might be a heat exchanger). Core assemblies  38  typically require that the tubes thread through one or more supporting structures  40  (as shown, plates). Because the polymeric tube is flexible and bends under its own weight, misalignment of the tubes through the supporting structures  40  is a consideration. To overcome this, guide mandrel  42  containing guide rods  44  is positioned to support the individual tubes as they move through the supporting structures  40 . The guide rods  44  are positioned to pass through the supporting structures  40  and mate with the end of each tube in the vicinity of the conduit  36 . These guide rods  44  typically have a sharpened or pointed end to facilitate their placement within the tubes. Once inserted, it is not necessary for the guide rods  44  to actually be secured to the tubes. Instead the guide rods  44  are merely intended to counteract the effects of tube bending so that the tubes pass freely along the core assembly  38  and through the supporting structures  40 .  
         [0022]    The coordination of the operation of the various components described above is central to the automated manufacture of core assemblies. Directional movement of these components is illustrated with arrows in FIG. 2. The cartridge  34  is supplied with tubes of a specified length in one or more of the columns  35 . The cartridge  34  is moveable (typically powered by a motor) to present tubes between the ram  32  and the positioning device  10 . A controlled movement of the core assembly  38  is accomplished through any of a number of techniques known to those of skill in the art, such as an actuator assembly. As tubes exiting from the conduit  36  are inserted into position in a core assembly  38 , the actuator then repositions the core assembly to receive another set of tubes therethrough. It will be appreciated that the actuator can position the core assembly  38  in any position in a plane (for example, up-down and left-right) as may be required to locate the tubes at positions in the core assembly  38  as selected by the designer.  
         [0023]    Typically and in operation each of the cartridge  34 , positioning device  10  and conduits  36  contain tubes. As the ram  32  urges tubes from the cartridge  34  into the positioning device  10 , this action in turn displaces the tubes contained in the positioning device  10  into the conduits  36 . This motion then pushes the tubes previously contained in the conduits  36  into the core assembly  38  (and in alignment along the supporting structures  40  with the assistance of the guide rods  44 ). The guide mandrel  42  is withdrawn to allow for this overall advance of the tubes through the system. Once this cycle is completed, the ram  32  is restored to its original position, and the cartridge  34  is moved to align the ram  32  with a column  35  containing additional tubes. The core assembly  38  is also repositioned to provide a location for the next set of tubes to be inserted. Once the core assembly  38  receives the requisite amount of tubes, it is withdrawn from the assembly and a new core assembly  38  is inserted in its place.  
         [0024]    The assembly can be operated in conjunction with a feed hopper such that columns  35  of tubes in cartridge  34  are pushed by subsequent columns of tubes which are in turn are pushed by the ram  32 . Feeding a new column  35  of tubes after every threading step (eg placement of a column of tubes into the core assembly  38 ) thus allows the device to be operated in a continuous manner.  
         [0025]    The positioning device  10  may be constructed from any number of materials. Metals offer obvious benefits in rigidity for guiding the tubes along a precisely defined path. Aluminum is a preferred metal for this purpose. The surfaces of the channels  14  and passages  18  may be smooth or textured. One advantage of a specially designed textured surface can be to minimize the area of contact between the tube surface and the passage surface, thereby minimizing the friction and abrasive effects. Optionally lubricants may be used either to the channels and passages of the positioning device  10  or to the tubes themselves, to counter any abrasive effects in the transport of the tubes through the device. However care should be exercised in selecting and using any lubricants so as to not degrade or otherwise deleteriously affect the tubes and their function.  
         [0026]    Having reference to FIG. 3, a variety of design possibilities for the positioning device  10  are contemplated herein. This figure offers side views of the ends of one or more surfaces  12  and second surfaces  22 , and depicts the passages  18  formed therein. In one arrangement, the surface  12  and the second surface  22  are identical to one another and when brought together form the channels  14 , tapered surfaces  16 , and passages  18  of desired pitch. The illustrations depict in cross section the passages  18  as circles, diamonds and ovals, all formed by the joinder of the surface  12  and the second surface  22 . It is also possible to use an array of multiple positioning devices  10  used in concert, in which case the array so formed might receive tubes from a plurality of columns  35  of cartridge  34  (or other receptacle) and in turn urged by a plurality of rams  32 . In another embodiment, a first surface  12  may be formed on both sides of one positioning device  10 . Other embodiments (as shown) can be crafted to suit a variety of design possibilities, including passages that are offset versus adjacent passages, passages formed using a planar second surface, passages formed on one surface that are sufficiently formed to contain tubes without requiring a second surface, and the like.  
         [0027]    Having reference to FIG. 4 herein, two styles of rams  32  are shown. The tubes may be fed to the positioning device  10  in a planar manner (meaning all tube ends enter the channel  14  of positioning device  10  simultaneously). In such a scenario the ram  32  is shaped as a uniform, flat surface at the contact point with the tubes. The tubes advance along the apparatus and are placed in the core assembly  38 . However because the tubes may not all travel the same distance (due to the configurations of the passages  18  along the positioning device  10 ) the ends of the tubes may become offset relative to one another once they travel through the passages  18 .  
         [0028]    If this is not a desired result, then the rams  32  may be styled to include staggered surfaces, as shown in FIG. 4. By incorporating such stepped or staggered rams  32  into the assembly, tubes of equal length can be inserted through the positioning device  10  and even though they may travel different distances nevertheless are not offset relative to one another after passing therethrough. It is readily appreciated that the selection of any number of designs of the ram  32  and the passages  18  may be conducted to accomplish a particular tube arrangement for an application of interest.  
         [0029]    There are several advantages associated with the assemblies and process of the present invention. It allows for the handling and automated processing of relatively flexible tubes. It is very robust with coordinated moving parts including the ram  32 , the cartridge  34 , the core assembly  38 , and the guide mandrel  42  (all under control of various motors and actuator assemblies). Changing the pitch or relative positioning of the tubes merely requires simple substitution of the machined positioning device  10 . The device is thus easily adaptable in commercial production settings.  
       EXAMPLE  
       [0030]    Polymeric tubes (in one embodiment monolayer tubes of polyamide 66; and in another embodiment multi-layer tubes consisting of polyamide 66/a tie layer/LCP) represent different degrees of flexibility. The tubes of each embodiment were 2.7 mm diameter and 0.2 mm wall thickness. A plastic tube sheet with 2.74 mm holes arranged in a staggered manner was placed in front of the positioning device  10  so that these holes were in alignment with the passages  18 .  
         [0031]    Using the assembly shown in FIG. 2 and the positioning means shown in FIG. 1, nine tubes were threaded at a time in a stepwise manner achieving a rate of 1 feed step per 10 seconds. This rate can, of course, be increased by increasing the tube feed and push rates. The butting ends of one column of tubes (located in the cartridge  34  or the positioning device  20 ) pushing against an adjacent column of tubes (located in the positioning device  20  or the conduits  36  respectively) did not result in any damage to the ends through the threading process.  
         [0032]    It is readily appreciated among those having skill in the art to which the invention pertains, that any number of modifications and variations can be made to the invention described herein. Such modifications and variations are contemplated as within the scope and spirit herein.