Heat exchanger fin forming machine

Abstract

What is disclosed is a fin forming machine for making fins for heat exchanger cores, or the like, in which the fin forming machine has three major drives and separate controls; the top and bottom drives control the vertical opening and closing of fin forming dies under programmable control in accordance with CNC technology; and a center drive under the control of a separate programmable system which controls horizontal movement of the feedstock into intersection with the top and bottom forming dies to incrementally halt the movement of the feedstock as it intersects with the forming dies upon convergence during fin formation and then advances it a controllable distance for the next fin forming action. These three drive systems being seamlessly variable and controllable during operation, maintain a high degree of calibration of the formation of each fin to maintain fin height and spacing within very close tolerances, which calibrations are achieved without shutting down machine operation. Positive control of all drive systems minimizes overtravel of the forming dies.

Claims

1. Apparatus for forming a continuous sheet of material into a horizontal series of uniformly-sized folded fins, comprising: a set of forming dies positioned for moving along a vertical axis of said apparatus, said set of forming dies including an upper die and a lower die and being mounted upon an upper slide assembly and a lower slide assembly; means for moving a sheet of material along a horizontal axis of said apparatus to a location wherein the horizontal axis and the vertical axis intersect, said means for moving a sheet of material being programmably operative for halting horizontal movement of the sheet of material; and, means for moving said set of forming dies together for converging upon the sheet of material at an intersection of said horizontal axis and said vertical axis when the horizontal movement is halted, thereby forming said series of uniformly-sized folded fins; and further including programmable means for independently controlling said top drive motor and said bottom drive motor for moving said top and said bottom dies a distance sufficient for achieving, upon convergence, uniformly-sized folded fins.

2. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 1 wherein said means for moving a sheet of material along a horizontal axis comprises: program means for controlling horizontal displacement of the sheet of material in increments; said program means including means for halting the horizontal displacement of the sheet of material upon each incremental movement, thereby providing a series of vertical fins of a chosen size within said series of fins.

3. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 2 wherein; said means for vertically moving said set of forming dies together for converging upon the sheet of material at an intersection of said horizontal axis and said vertical axis includes means for controlling vertical travel of said upper slide assembly and said lower slide assembly toward convergence so that depth of engagement of said upper die and said lower die upon convergence is controllable for precisely setting the height to which each said uniformly-sized fin, within a series of fins, is formed.

4. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 3, further comprising; means for vertically controlling said upper slide assembly and said lower slide assembly following convergence upon the sheet of material at an intersection of said horizontal axis and said vertical axis, so that said upper die and said lower die diverge only a distance marginally greater than the height of a last formed fin.

5. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 3, wherein; said means for moving said set of forming dies along a vertical axis of said apparatus includes programmable controls for said top and bottom drives, wherein said moving means for said top and said bottom dies includes control means for moving said dies distances adequate to achieve selectable variable sizes of folded fins.

6. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 3, wherein said means for moving a sheet of material along a horizontal axis comprises: programmable means for controlling horizontal displacement of the sheet of material, and programmable controls for setting said incremental displacement, means for temporally halting the horizontal displacement of the sheet of material upon each incremental movement; and, wherein said programmable controls for setting incremental horizontal displacement are continuously operative to achieve uniform horizontal displacement between successively folded fins in a series of fins.

7. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 3, wherein said means for moving a sheet of material along a horizontal axis comprises: programmable means for determining the number of successively formed fins which have been formed; and further comprises programmable means for signaling a point along the horizontal axis for cutting the sheet of material following the formation of a series of formed fins.

8. The apparatus for forming a continuous sheet of material into a series of uniformly-sized folded fins according to claim 1 or 3 or 5, wherein said means for moving said set of forming dies along a vertical axis of said apparatus includes programmable controls for said top and bottom drives, and wherein; said moving means for said top and said bottom dies includes programmable controls for moving said dies distances adequate to achieve close tolerances of fin height of each fin within a series of formed fins.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) In the drawings, similar reference numerals and symbols denote similar features or elements throughout the several views:

(2) FIG. 1 is a diagrammatic representation illustrative of the basic elements and functions of the various parts of the fin forming machine.

(3) FIG. 2 is a flowchart of the controls of the overall machine from the operator input device to the endpoint where a completed, formed fin is produced.

(4) FIG. 3 is a graphical representation of a typical heat exchanger core, partially exploded, to illustrate the basic elements of a plate-frame heat exchanger.

DETAILED DESCRIPTION OF THE DRAWING FIGURES AND PREFERRED EMBODIMENTS

(5) Turning first to FIG. 3 of the drawings, this figure represents the basic pieces or elements of a typical plate and frame heat exchanger 10. The plate and frame heat exchanger consists primarily of three essential elements, flat plates 11, folded fins 12 and end or spacer bars 13. The bars 13 are situated at the extreme ends of each of the runs of formed fins 12. As will be seen in FIG. 3, the runs of fins 12 are alternately set transversely and longitudinally within the structure. The end bars 13 of a transversely oriented set of fins join with the end bars of the longitudinally oriented fins to form the aforementioned spacer bars. The vertical die dimension 13a of an end bars 13 provides the structural limitation of size on each run of formed fins when a run of fins is sandwiched between a first flat plate and the next adjacent flat plate and when these parts are brazed together into an integral unit, a fin-defined set of passageways is provided. The heat exchanger unit or core shown in FIG. 3 has four transverse fin passage elements in three longitudinally oriented fin passageways. The peripheral dimensions of the flat plates are defined by dimensions 11a-11b. As mentioned heretofore, prior to the compression and brazing steps of core construction, the vertical dimension 12a of fins 12 shall be greater than the vertical dimension 13a of end bars 13, as it is the function of the end bars 13 to provide the spacing between the run of fins and provide the outermost dimension of each fin stack. By providing the vertical dimension 12a of fins 12 one thousandths of an inch greater than the vertical dimension 13a of the spacer bars, proper contact of the entire edge of every fin with the adjacent plate, on the top and bottom of a set of fins is assured so that during the brazing process a proper bond is obtained along the entire length of every fin.

(6) Turning now to FIG. 1, the operation of the fin forming machine is described. The fin material is usually formed of aluminum having a thickness on the order of 0.060 to 0.080 and is normally provided in coils or rolls 20. The fin material feeds off of the roll 20 and passes through a lubricant bath 22 to facilitate the passage of the feedstock through the fin forming machine. Other forms of lubrication are contemplated such as lubricant misting, which may not be as environmentally acceptable. It will be seen that there are basically three drive motors which operate the machine; the top and bottom drive motors 24 and 26 control the vertical movement of the top and bottom dies 25 and 27. The center servo motor 28 controls the advance of the feed material 21 into the forming dies. Upon instructions entered by the operator which inputs information from a control panel which may be a touch screen, digital signals containing information on dimensional movements and timing are relayed to the three servomotors 24, 26 and 28 where these digital signals are converted into linear motion. This manner of conversion and the control by servomotors is typical of that employed in other CNC machine control mechanisms employing techniques well known in the art. The vertical motion of the top forming die 25 and bottom forming die 27 may each be incrementally and seamlessly adjusted to obtain the desired depth of convergence of the dies 25 and 27 so as to accomplish a desired fin height. Similarly, instructions to the center servo motor 28 provide information to an internally contained programmable cam assembly 31 located in the center servo motor mechanism which controls a piston rod 30 to provide side to side movement or incremental forward movement of the sheet material as it is projected between the top and bottom forming dies. The center servo motor advances the sheet of material to a position between the forming dies where it momentarily halts the movement while the top and bottom dies are converged to fold a fin and then removed, whereupon central server motor advances the sheet material incrementally forward again. The distance the sheet material 21 is advanced between top and bottom forming dies is controlled by the central servo motor programmable cam which can be variably adjusted according to the digital signals sent to it through the computer program under the control of the operator input. This controls the spacing between successive fins, and likewise controls the rate of advance of the material through the fin forming machine. Positive control exercised over the top and bottom servomotors provides precise control over fin height. The control of the top and bottom drive motors 24 and 26 also determines the amount by which the top die 25 and bottom die 27 diverge to clear a previously formed fin. In the preferred embodiment of the invention the control of the top and bottom drive motors discretely controls the amount of divergence of the top and bottom forming dies so that no more motion is required to clear a formed fin than is necessary. In this way the present invention differs from the prior art in that the prior art devices are not known to have any limitation on the movement of the top and bottom forming dies but rather merely move as far apart as mechanically possible. That resulted in a great deal of lost motion and an unnecessary consumption of power and therefore energy.

(7) As heretofore explained, by providing precise, variable control of the device drivers for the top, bottom and center drive motor, the precise height and spacing of folded fins can be maintained within 0.001 inch of the desired fin height. Moreover, through the operator input control interface, fin height that is continuously monitored may be adjusted during operation so that the desired tolerances are always maintained without any down-time for recalibration. The reduction in the divergence distance between the top and bottom forming dies after fin formation achieves a smoothness of operation as well as an economy of motion wherein the top and bottom dies separate from one another only so much as is necessary to allow the formed fins to pass between them. This mechanism allows the aluminum sheet to move more uniformly and quickly through the dies with the least amount of wasted motion with a substantial reduction in energy consumption in that force is applied only when required and only in the direction needed to form a fin. A secondary benefit of positive control over the drive motors is that the smooth operation yields a substantial reduction in noise and vibration compared to other prior art devices, thus increasing the environmental quality of the workplace. By providing positive control of movement and therefore of the tolerances required for proper fin formation, the present device eliminates the downtime prior art devices previously required to allow for readjustment and recalibration of the mechanical systems. Equally important, positive control over fin height is achieved to a much greater degree such that the number of heat exchanger cores failing the post-fabrication pressure tests is substantially reduced, resulting in an economy of wasted material and increasing the overall economy of production. In addition, the control mechanism of the horizontal drive motor also may measure the number of fins formed so as to provides a marker to signify the achievement of a desired length of fins so that manual measurement is not necessary to determine where to cut the formed fins into a desired length.

(8) Turning now to FIG. 3 of the drawings, a flowchart of the basic features of the control system is set forth. The features of the computer control system and the logic steps performed should be self-explanatory from FIG. 3. The basic operation is as follows: the operator inputs coordinate figures into the operator control interface panel 39, which then passes the information through the proprietary computer program 40 which directs the individual coordinate information through the ACR control 41 which directs the information in digital format to the top, middle and bottom servo (drive) motors 24, 28 and 26 respectively. Information delivered to the servo drives on the three servomotors 24, 28 and 26 converts each digital signal into linear motion which controls the top, middle and bottom positioning devices to control their horizontal and vertical positioning in accordance with conventional CNC control technology. While control of the top and bottom slide assembly and control motors follows fairly conventional CNC technology and techniques, with respect to the middle drive, there are additional control features. The center servo motor 28 includes a programmable cam/camshaft 31, and this is exemplified in FIG. 2 by the custom positioning assembly controls 42 which include a custom cam and the drive link assembly control 43 which controls the action of the slide assembly along the middle or horizontal axis which gives directions to the custom forward horizontal positioning die assembly 45. This control drive and its program provides directions to the horizontal drive assembly to provide incremental forward movement and can be adjusted through the programming means so that the servo motor 28 incrementally advances the fin material through the tooling dies. The variable adjustment of the camshaft 31 in the center control drive may be fully programmed so as to determine the distance between the tooling teeth, which provides that the desired spacing between the fins. In other words, the programmable camshaft provides information which adjusts the center drive motor, in effect by varying the effective length of the camshaft 31, to advance the sheet material the desired distance, whereupon it momentarily halts for the convergence of the top and bottom dies to form a fin and then determines the amount by which the feed material will be advanced until it stops again for the next fin formation, thereby establishing the desired spacing between each fin.

(9) While discrete embodiments of the present invention have been shown and described it will be apparent to those skilled in the art that there a number of ways that the objectives and improvements described for the present invention can be accomplished; and it is therefore contemplated that the invention is not limited to the preferred embodiments shown and described herein, but that the invention be defined by the accompanying claims.