Patent Publication Number: US-6212764-B1

Title: Link bending machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to machines for fabricating heat exchangers. More particularly, the present invention relates to a machine for bending links projecting from heat exchangers. 
     2. Disclosure Information 
     Plate-fin heat exchangers are well known in the art. In these types of heat exchangers, a plurality of elongated plates are joined together, such as through a lamination process to define a plurality of passageways for the movement of a fluid therethrough. Each of the passageways is formed by the inwardly facing surfaces of a pair of joined plates. The interior surfaces of the joined plates generally define a central fluid conducting section. The passageways are interconnected so that a fluid may flow through the plurality of joined plates forming the heat exchanger. As is also known in the art, conductive fin strips are located between outwardly facing surfaces of the pairs of joined plates. Heat exchangers of this type have particular utility as evaporators for air conditioning systems of motor vehicles. 
     It is known to manufacture these types of heat exchangers from a plurality of interconnected plate members, stamped from a sheet of deformable material. U.S. Pat. No. 5,507,338, assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference, teaches one such method of folding a plurality of plate members in a zig-zag or bellows-like fashion to fabricate a heat exchanger core. A plurality of links interconnect the plate members. Upon folding, these links project from the heat exchanger core, making it difficult to stack cores one upon another without damaging an adjacent core. It would therefore be desirable to minimize the links and the amount the links project from the folded core. 
     It is an object of the present invention to provide a machine which can bend the tab members extending from the core against the core to minimize the damage to the heat exchanger and to surround components. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems associated with the prior art by providing a machine for bending a first set and a second set of folded deformable links projecting outwardly from a heat exchanger core made from a continuous strip of preformed, generally planar plates interconnected together in a bellows-like manner by the first and second set of folded deformable links. The machine comprises a base, a transport mechanism for transporting the core to a workstation, a locking mechanism for locking the core in a predetermined orientation in the workstation, and a bending mechanism attached to the base for bending the first set of folded deformable links against the core in a direction generally perpendicular to the plane of the plates and for bending the second set of folded deformable links in a direction generally parallel to the plane of the plates. In one embodiment, the bending mechanism for bending the first set of deformable links against the core further includes a reciprocating die which applies a force against the first set of deformable links in a direction perpendicular to the plane of the plates. 
     It is an advantage of the present invention to provide a machine which minimizes the amount tab members project from the heat exchanger by bending the links against the core. These and other objects, features and advantages of the present invention will become apparent from the drawings, detailed description and claims which follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a heat exchanger structured in accord with the principles of the present invention. 
     FIG. 2 is a to plan view showing a portion of a strip of preformed plates. 
     FIG. 3 is a side view showing a portion of a strip of preformed plates being folded into a core. 
     FIG. 4 is a side view of a machine for folding the strip of plates into a core. 
     FIG. 5 is a top plan view of the machine of FIG.  4 . 
     FIG. 6 is a top plan view of a heat exchanger structured in accord with the principles of the present invention prior to the links being folded. 
     FIG. 7 is a top plan view of a heat exchanger structured in accord with the principles of the present invention after the links have been folded. 
     FIG. 8 is a top plan view of a machine for bending the folded links in accord with the present invention. 
     FIG. 9 is a side view of the machine of FIG.  8 . 
     FIGS. 10A and B are enlarged views of a portion of the machine of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIG. 1 shows a plate-tube heat exchanger, generally designated by the numeral  10 , in the form of an evaporator particularly adapted for use in an automobile air conditioning system. The heat exchanger  10  comprises a stack of formed, elongated plates  12 , pairs of which are joined together in face-to-face relationship so that adjacent pairs provide alternate passageways for the flow of refrigerant therebetween as will be described further below. The plates may be joined in any of a variety of known processes, such as through brazing or a lamination process. Heat transfer fins  14  are positioned between joined pairs of plates  12  to provide increased heat transfer area as is well known in the art. The joined plate pairs and fin assemblies are contained within endsheets  16 . 
     The heat exchanger  10  includes an inlet port  20  and an outlet port  22  formed within a header  18  at either one or both ends of the heat exchanger  10 . The header is in direct communication with the passageways between the joined pairs of plates  12  as will become apparent from the following description. The plates  12  have aligned apertures at the ends thereof providing communication between inlet and outlet ports  20 ,  22 , respectively, of header  18 . However, as is well known in the art, each of the plates can include apertures at either one or both ends thereof and the inlet and outlet ports  20 ,  22  can be located at opposite ends of the heat exchanger as is well known in the art. In the heat exchanger FIG. 1, refrigerant is directed into the inlet port  20 , passed through the pair plurality of joined plates  12  in a known manner. The refrigerant then exits through outlet ports  22  to complete the cooling cycle. 
     As shown in FIG. 2, the plate members  26  are formed from a single sheet of material  24  and are interconnected by a first set of deformable links  27  and a second set of deformable links  29  which will be described in greater detail below. Each of the plates  24  is generally planar and include a longitudinal axis denoted by line L—L and a transverse axis denoted by line T—T. The longitudinal axis of the plates (L—L) is parallel to the longitudinal axis of the heat exchanger core. Stated another way, the longitudinal axis of the heat exchanger core is perpendicular to the general direction of air flow passing through the core. The material  24  can be an aluminum material coated with an aluminum brazing alloy as is known in the art. A sheet of material  24  can either be of a predetermined length with a predetermined number of plate members  26  therein or may be formed as a continuous strip of material which is cut at a predetermined number of plates to form a heat exchanger of predetermined size. The plate members  26  are stamped using pneumatic and/or hydraulic activated details in a die controlled by a PLC\PLS or other computerized means known in the die pressing art. 
     Each of the plate members  26  includes a pair of end portions  28  and an intermediate portion  30  therebetween. A plurality of apertures  32  can be formed in each of the end portions  28  or alternatively, a single aperture can be formed therein. The apertures are aligned when the heat exchanger is assembled to provide for a fluid conduit for the heat exchanger fluid to pass therethrough. As shown in FIG. 2, the central aperture includes a radius portion. The radius portion provides for alignment of the inlet tube during its insertion into the core during the assembly process. Each of the intermediate portions  30  of the plate members  26  includes a plurality of beads  34  which, as is well known in the art, provide a circuitous path for the fluid to pass through the plate tube  12  to increase the turbulence of the fluid and provide for better heat transfer characteristics. 
     As further shown in FIG. 2, selected end portions  28  of plate members  26  include end portions in which the apertures  32  are not included. These blanked ends  36  provide a baffle means in the heat exchanger by not allowing the fluid to pass thereby, forcing the fluid to assume a new flow direction within the heat exchanger. This provides an advantage over known heat exchangers without the baffle means which may not work as effectively as the present invention. At the time the plate members  26  are formed, it is determined which of the selected end portions of the plate members are blanked (at  36 ) to form the baffle means of the heat exchanger. The manifold plates are then also formed. 
     As shown in FIG. 2, the deformable links  27  and  29  are indented at predetermined locations to form a series of preferential bend zones indicated by dashed lines  58 ,  60 . The bend zone indicated by dashed line  60  is the preferred bending zone when adjacent pairs of mating plates are to be folded face-to-face. The bend zones indicated by dashed lines  58  are the preferred locations at which the links  27 ,  29  are to be bent between pairs of mating plates. The distance between the bend zones  58  is preferably the same distance as the thickness of the fin members  14  to be inserted between the pairs of mating plates. 
     The formation of the core element of the heat exchanger  10  can be accomplished by a corrugation machine. An example of one such machine which can be used to form a heat exchanger core is shown in FIGS. 4 and 5. Referring back to FIG. 3, the deformable links  27 ,  29  of the continuous strip of alternating plates are initially folded in a folding area by a fold forming machine to impart to the continuous strip an initial corrugation. The initial corrugated strip is then gathered in a gathering area by a gathering mechanism in which the folding of the deformable links is substantially completed and which results in a first set of folded deformable links and a second set of deformable links. The difference between the first and second set of deformable links results from the different bending zones,  58  and  60 , located in each link. These differences will be described in greater detail below. Fin members  14  are then inserted between adjacent plate tubes by a fin stuffing machine. 
     To form a heat exchanger core with a predetermined number of plate tubes, one set of each of the first and second set of deformable links is cut off after a desired number of plate tubes has been completed. FIGS. 4 and 5 illustrate one example of a corrugation machine for fabricating such a heat exchanger core. The corrugation machine  100  has a base  102  including a feed mechanism  104  provided at one end for feeding the strip containing preformed plates to a material guide  106  which longitudinally aligns the strip in the machine, a fold forming mechanism  112 , a gathering mechanism  116 , a fin stuffing mechanism  120  and a link cut-off device  124 . 
     The corrugation machine  100  includes a process control monitor  108  and a fold forming mechanism  112 . The process control monitor may be an optical or mechanical device adapted to detect predetermined plates such as the end plates of a core element and to count the number of plates between the predetermined plates to assure that each core severed from the continues strip of preformed plates will have the proper number of plates. The fold forming mechanism  112  consists of two pairs of opposing tractor or caterpillar drives  114  disposed on opposite sides of plates  12 . The drives include lugs which engage the plates  12  such that as the drives rotate, the plates are caused to begin folding at the deformable links  27 ,  29 . 
     The gathering of the folded plates after they exit the fold forming mechanism  112  is accomplished by a pair of gathering belts  116 ,  118  (FIG.  5 ). Each of these belts has an upper and lower belt including lugs for engaging the plates and controlling the folding between mated pairs of plates as well as between individual plates. After leaving the gathering mechanism, corrugated fins are inserted between mated pairs of plates. This is accomplished by a fin stuffing machine  120  which collects a predetermined number of fins corresponding to the number of spaces between mated pairs of plates. The fins are then dropped or pushed by the stuffing machine  120  into appropriate spaces between mated pairs of plates. An electronic controller  130  controls the number of fins aligned in the stuffing machine and the placing of the fins into the heat exchanger core. After the fins are stuffed into the core, the gathering belts are restarted to transport a new batch of folded plates under the fin stuffing machine. 
     After a predetermined number of mated plate pairs have been stuffed with fins and folded, a link is cut to separate this formed core from the next adjacent core. The folded links are cut at both ends of the heat exchanger core, but only those links between adjacent cores are cut. 
     FIG. 6 shows a top plan view of one end of the heat exchanger core  10  after the core has been through the link cut-off machine. As shown, the core includes a plurality of folded links projecting outwardly from the core. These links include a first set of links  70  and a second set of links  72 . The first set of folded links  70  is formed at bend zones  58  and separate adjacent, mated pairs of plates to define the open space into which the fin members  14  are placed. The first set of folded links  70  are more open than the second set of folded links  72 . The second set of folded links  72  are formed at bend zones  60  which act to mate two adjacent plate members to one another to form a plate tube. Because the mated plates must be physically connected to an adjacent plate, the second set of folded links  72  are somewhat more narrow than the first set of links  70 . 
     If these projecting folded links  70 ,  72  were left as is, they would interfere with packaging, such as a heat exchanger case, when inserted into such. Also, during transport of the cores  10  to a brazing furnace or for use in assembly, the cores  10  are often stacked one upon another. These projecting folded links interfere and get tangled with adjacent, stacked cores, often resulting in punctured or damaged heat exchanger cores. To overcome this problem, the projecting links are folded against the heat exchanger core such as is shown in FIG.  7 . 
     FIG. 7 shows that both of the first  70  and second  72  sets of folded links are folded against the heat exchanger core and do not extend or project outwardly as far from the core as before. Each plate member  12  is a generally planar, elongate member having a longitudinal and traverse axes. Fluid flow through mated plate pairs (plate tubes) typically is parallel to the longitudinal axis of the plates. Keeping this orientation, the first set of folded links  70  are folded against the core in a direction generally parallel to the longitudinal axis of the plate members. The second set of folded links  72  are folded in a direction different than the first set of links  70 , although they could be folded the same. In the preferred embodiment, the second set of links  72  are folded in a direction generally perpendicular to the longitudinal axis of the plates  12 , in a direction generally parallel to the transverse direction of the plates  12 . 
     FIGS. 8-10 show a machine for bending the folded links according to the present invention. The machine  76  can be an integrated part of the corrugation machine described in FIGS. 4 and 5, or may be a stand alone machine. After the heat exchanger cores  10  leave the link cut-off machine  124  and before they are sent to a brazing furnace, the cores are transported to the link bending machine  76 . The machine  76  has a base  78  and a transport mechanism  79  for transporting the cores  10  to the work station  80  in the machine. After the cores  10  are transported to the machine  76 , the cores are locked into a predetermined orientation by reciprocatory hydraulic or pneumatic rams  85 , one which exposes the first set of folded links  70  outwardly from the machine  76 . A reciprocating die or punch  82 , activated hydraulically or pneumatically, engages the entire first set of folded links  70  and applies a force against the first set of links  70  in a direction generally perpendicularly to the plane of the plate members. This causes all the links in the first set  70  to bend instantaneously in a direction generally parallel to the longitudinal axis of the plate member  12 . 
     Next, a pair of rollers  81  are urged against the second set of folded links  72 . In contrast to the punch which bends all the links  70  in the first set simultaneously, the pair of rollers  81  fold each of the links in the second set serially, or one after another. The rollers  81  apply a force against the links  72  in a direction generally perpendicular to the plane of the plates  12  and bend the links  72  in a direction generally parallel to the transverse axis (T—T) of the plate  12 . As shown in FIG. 10A, the rollers  81  rotates at the end of a rigid arm  83  which can be hydraulically or pneumatically controlled. The arms  83  move fore and aft to contact the links  72  and reciprocate in a vertical, up-and-down direction to bend each of the links  72  serially. In another embodiment of the invention, the rollers  81 ′ can selectively engage and disengage the second set of links  72 . In some embodiments, the heat exchanger core  10  includes fluid manifolds (inlet and outlet) which project from the middle of the fluid tanks as opposed from the ends. With this design, the fluid manifolds are spaced between and project through the second set of folded links  72 . The rollers  81 ′ must be able to navigate around these manifolds to bend the links  72  without causing damage to the manifolds. FIG. 10B shows a design of a roller  81 ′ which can accomplish this. The rollers  81 ′ includes a flexible member  84  which contains a sensor. The sensor, either optical or mechanical, determines the presence of the manifold or other obstruction and sends a signal to a controller which raises the rigid arms away from the core. After the obstruction has passed, the controller causes the arms and rollers to engage the links once again. Alternatively, the rollers  81 ′ can be preprogrammed so that the controller automatically raises and lowers the rigid arms to avoid the manifold or other obstructions. 
     After the links have been folded, the core is then placed into a brazing furnace and passed through a brazing operation in which the metal brazes together in order to form the completed article. 
     Various modifications and alterations of the present invention will, no doubt, occur to those skilled in the art to which this invention pertains. These and all other variations which rely upon the teachings by which this disclosure has advanced the art are properly considered within the scope of this invention as defined by the appended claims.