Abstract:
A method for producing a duct from a planar board having two opposed substantially parallel edges with metal foil facings on opposed major surfaces of the board is disclosed. The method comprises making planar cuts through one of the metal foil facings and at least most of the planar board there below to produce a blank with 3 parallel “V shaped grooves which are parallel to angled edges of the blank. A duct is formed by folding the blank so that the “V” shaped grooves form three of the edges of the duct, and the angled edges form the fourth of the edges.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to methods and apparatus for converting flat boards for use in constructing ducts and duct fittings. The methods and the apparatus are particularly well suited for use with boards that are rigid or semi-rigid and are produced specifically for use in fabricating insulated ducts for heating, ventilating and air conditioning applications. 
     2. Description of the Prior Art 
     Boards that are commercially available today are being produced for use in forming thermally insulating ducts such as are employed for heating, ventilation and air conditioning. In one case, these boards consist of a rigid foamed plastics material, namely, a closed cell expanded phenolic foam in the form of a planar board having a metallic foil such as aluminum bonded to each major surface. One example of such a board is sold under the trademark KOOLDUCT®. The apparatus and methods of the present invention are especially well suited for use with such planar boards although the methods and apparatus are also suitable for use with other foil faced planar boards, for example, boards consisting of open cell or closed cell expanded foam materials, such as polyurethanes. Such boards are referred to herein generally as “foam boards”. They are to be distinguished from other duct materials such as sheet metal and fiber board typically made from glass fibers with resins and/or binders to provide stiffness. 
     The fabrication of ducts and duct fittings from foam boards is quite different from the fabrication of ducts and duct fittings from conventional metal sheets. For one thing, sheet metal can be treated fairly roughly and foam board, in general, tends to be more fragile and frangible than sheet metal and some extra care needs to be taken in handling foam board and in fabricating ducts and duct fittings from it. However, foam board is remarkably light, with excellent thermal insulating properties, and often sufficiently rigid itself for duct applications although long unsupported spans, large cross-sectional areas, or significant differential pressures between interior and exterior may require reinforcement or additional support. There are numerous other advantages to foam board in heating, ventilating and air conditioning applications, vis-à-vis sheet metal and fiber board, as well. Foam board is very robust. Ducts made from it can handle pressures of up to four inches of water column. Accordingly, better fabrication apparatus and methods are needed to expand the use of this important material. 
     SUMMARY OF THE INVENTION 
     The present invention is a machine based system for precutting foam board for producing parts from which ducts and duct fittings can be readily produced. The invention, in one aspect, is an improved method for producing a duct from a planar board having two opposed substantially parallel edges with metal foil facings on opposed major surfaces of the board. The method comprises the steps of making a plurality of planar cuts through one of the metal foil facings and at least most of the planar board therebelow to produce a blank with n parallel “V” shaped grooves which are parallel to angled edges of the blank, the walls which are adjacent the “V” shaped grooves intersecting one another at an angle of substantially 360 divided by n plus 1 degrees, and a plane which intersects the bottom of one of the angled edges of the blank and is parallel to the opposed angled edge of the blank forms the same angle with the wall it intersects, and forming a duct by folding the blank so that the “V” shaped grooves form all but one of the edges of the duct, and the angled edges form the last one of the edges of the duct. Usually, the duct has four sides, and the angle between adjacent sides is 90 degrees. 
     In another aspect, the invention is apparatus for processing foam boards having a central core composed of a cellular body and parallel top and bottom layers of an impervious material adhered to the central core. The apparatus comprises a work table, means for supporting a work piece above the table so that there is a plenum between the bottom of the foam board work piece and the top of the table, means for withdrawing air from the plenum to establish and maintain a vacuum therein, a cutter, means for causing the cutter to undergo straight-line translational movement relative to the foam board being processed where the straight line is parallel to the top and bottom impervious material layers, and means for supporting the cutter so that it is operable to cut the foam board being processed to each of a plurality of distances above or below one of the impervious material layers. 
     In still another embodiment, the invention is a foamboard sheet having cuts which extend therethrough and constitute edges of the bottom, of the top, and of two sides of a duct which can be produced from the board, The sheet also has cuts which extend only part way therethrough and constitute parts of the ends, of the bottom, of the top, and of two sides of the duct which can be produced from the board. The foamboard sheet can be shipped to a construction site, the duct parts can be cut therefrom, and the duct can be assembled from the parts. 
     The invention is also concerned with a workpiece hold down system for a three axis cutting machine. The hold down system comprises a work table having an upper surface, a plurality of pegs for supporting a work piece in spaced relationship with the work table upper surface so that a plenum is defined between the work table upper surface and a major surface of the work piece. Vacuum ports connect the plenum and a vacuum system connected to withdraw a sufficient quantity of air from the plenum to increase the frictional engagement between the pegs and the work piece so that the work piece is held fast on the pegs, even while the cutting machine removes portions of the work piece. Preferably, the vacuum system is of the centrifugal blower type. 
     The invention is a method for converting foam board for the production of duct work comprising the steps of supporting a foam board on a work table provided at a first location and removing material from the foam board to define elements of the duct work. Some material is removed from the foam board by the formation of straight cut channels that do not extend entirely through the foam board so that the board remains intact in the vicinity of the straight cut channels, and remains in one piece. Thereafter, the foam board with straight cut channels is transported to a second location, and a hand tool is used to cut entirely through the foam board in the locations of the straight cut channels, to separate the foam board into duct work component pieces. 
     Accordingly, it is an object of this invention to provide a system for accurately and easily producing such parts. 
     It is another object of the invention to provide such a system in which pieces are defined by cuts made in a workpiece wherein the pieces remain in the workpiece while they are transported to a job site. 
     It is yet another object of the invention to provide a system where a hand tool can be used on site to easily and accurately separate the duct pieces, previously cut off site, from one another and from scrap in the workpiece for assembly and installation on site. 
     These and other objects and advantages of the invention will be apparent from the following detailed description of the invention including the preferred embodiments, reference being made therein to the attached drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         FIG. 1  is a top view of apparatus according to the present invention for pre-cutting foam board; 
         FIG. 2  is a side view, partially in cross-section, of a cutter and motor and a portion of a foam chip removal system which are part of the apparatus shown in  FIG. 1 ; 
         FIG. 3  is a top view of a work table and a workpiece hold down system which are part of the apparatus shown in  FIG. 1 ; 
         FIG. 4  is a view, partially in cross-section, of a cutter cutting a workpiece according to one aspect of the method of the present invention; 
         FIG. 5  is a view, partially in cross-section, of a cutter cutting a workpiece according to a second aspect of the method of the present invention; 
         FIG. 6  is a view, partially in cross-section, of a cutter cutting a workpiece according to a third aspect of the method of the present invention; 
         FIG. 7  is a top view of foam board after it has been precut according to the present invention for later assembly into a straight section of duct; 
         FIG. 8  is an end view of the precut foam board shown in  FIG. 7  before it is assembled into a straight section of duct; 
         FIG. 9  is a perspective view of a hand held cutter used in the method of the present invention; 
         FIG. 10  is a bottom view of the cutter shown in  FIG. 9 ; 
         FIG. 11  is a side view of the cutter shown in  FIG. 9  as it is cutting foam board according to the method of the invention; 
         FIG. 12  is an end view of the cutter shown in  FIG. 9  as it is cutting foam board according to the method of the invention; and 
         FIG. 13  is a top view of foam board after it has been precut into four intricate pieces according to the present invention to be removed from the foam board and assembled into a duct fitting. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now in more detail to the drawing figures,  FIG. 1  shows a three axis (X, Y and Z) cutting machine indicated generally at  10  and including a work table  12  supported on a frame, side members of which are indicated at  14 . A gantry  16  is supported relative to the table  12  for movement in the “Y” direction (up and down in  FIG. 1 ) under the action of tandem stepper motors  18  mounted on the gantry  16  for movement therewith relative to the frame members  14  and, specifically, relative to tracks  20  supported thereon. It will certainly be appreciated that other Y axis actuators or actuator systems, now known or hereinafter developed, may be incorporated in the apparatus  10  to effect movement of the gantry  16  in the Y direction. 
     Mounted on the gantry  16 , for movement therewith, is a tool carriage indicated generally at  22  and comprising an X axis actuator  24  for effecting movement of the carriage  22  in the “X” direction (left and right in  FIG. 1 ) relative to the gantry  16  and relative to a track  26  mounted on the gantry  16 . Again, it will certainly be appreciated that other X axis actuators or actuator systems, now known or hereinafter developed, may be incorporated in the apparatus  10  to effect movement of the tool carriage  22  in the X direction. 
     The tool carriage  22  ( FIGS. 1 and 2 ) includes a Z axis actuator for effecting movement of a tool holder  30  and a tool  32  carried therein in the “Z” direction (up and down in  FIG. 2 ). Yet again, it will certainly be appreciated that other Z axis actuators or actuator systems, now known or hereinafter developed, may be incorporated in the apparatus  10  to effect movement of the tool holder  30  in the Z direction. 
     The X axis actuator, the Y axis actuator and the Z axis actuator are controlled by a programmable machine  34  that is operable to convert layout information into control signals that are delivered through a connector  36  to the apparatus and to the X, Y and Z actuators to control the position of a cutter  38  carried by the tool  32  relative to the work table  12  and a workpiece WP ( FIGS. 4 through 6 ) supported on the work table  12 . Under the control of the control signals, the actuators are operable to move the cutter  38  in a predetermined path to effect desired, predetermined removal of portions of the workpiece. The cutter  38  comprises two straight cutting edges which are ninety degrees offset from one another. 
     As shown in  FIGS. 4 through 6 , the workpiece WP may comprise a foam board  40  sandwiched between an upper fiber reinforced foil layer  42  and a lower fiber reinforced foil layer  44  secured to and covering upper and lower surfaces of the foam board  40 . Such workpieces are available commercially under the trademark KOOLDUCT® and this product is presently sold in thicknesses of 22 mm and 28 mm although other thicknesses may be introduced. This product is extremely light weight and, in order to process it on the cutting machine  10 , the workpiece must be held firmly and securely yet gently so that no damage befalls the workpiece. Also, as indicated above, other materials may be converted using the method and apparatus of the present invention. 
     In order to secure a workpiece on the work table  12 , the cutting machine  10  is equipped with a workpiece hold-down system and it comprises a series of support pegs  50  ( FIGS. 1 and 3  through  6 ) with upper surfaces  52 . The pegs  50  are inserted into bores in the work table  12  and it is preferred that the bores be spaced somewhat evenly and good results have been obtained with the pegs  50  and the bores spaced about 4 inches apart in a pattern corresponding with the pattern shown in  FIGS. 1 and 3 . As can be seen in  FIGS. 4 through 6 , the lower foil layer  44  rests on the upper surfaces  52  of the pegs  50  creating a plenum  54  between the foil layer  44  and the upper surface of the work table  12 . Air is withdrawn from the plenum through vacuum ports  56  which are openings that extend through the work table  12  and are in communication with conduits  58  that, in turn, are connected to the inlet of a suction based dust collector or some other vacuum source. It is preferred that a centrifugal fan based dust collector be used, for reasons discussed below. In  FIGS. 2 and 3 , Dust Collector refers to any suitable vacuum source, however. The negative pressure condition in the plenum draws the foil layer  44  and the workpiece WP into close contact with the peg surfaces  52  and holds the workpiece WP fast against the pegs  50 , even while the cutter  38  acts on the work piece. This workpiece hold-down system prevents movement of the workpiece WP in the X direction, the Y direction and the Z direction, relative to the work table  12 . The programmable machine may be used to control the establishment and dis-establishment of the negative pressure condition in the plenum  54 . 
     When the vacuum ports  56  are not withdrawing air from the plenum  54 , the workpiece WP will be supported on the pegs  50  but it will just be resting on them so that it can be lifted and removed from the machine  10 . It will be appreciated that the work table  12  and the work piece WP may be quite long and the removal of a large workpiece WP from the work table  12  can be facilitated by directing air under pressure against the lower foil later  44  of the workpiece WP. Referring to  FIG. 3 , a system is shown schematically for directing pressurized air against the bottom of a workpiece WP. In  FIG. 3 , some of the pegs  50  have been replaced by tubes  60  which extend through the work table  12  so that an upper end of each tube terminates in an end that is substantially the same height above the table  12  as are the upper surfaces  52  of the pegs  50 . Below the work table  12 , the tubes  60  are connected to one or more conduits  62  which are connected to a source for pressurized air (not shown) so that air under pressure can be selectively delivered to and up through tubes  60 , when desired, to lift the workpiece WP and facilitate its removal from the work table  12 . This can also be brought under the control of the programmable machine, if desired. A workpiece roller  64  ( FIG. 1 ) is positioned to help support a workpiece WP as it is delivered to or removed from the work table  12 . 
     Referring now again to  FIG. 2 , apparatus for collecting material that has been removed from a workpiece WP comprises a conduit  70  that provides communication between a cutter shroud  72  and a vacuum source, which is referred to in the drawing  FIG. 2  as a Dust Collector. The cutter shroud  72  is comprised of many long flexible bristles  74  supported on a shroud ring in a generally cylindrical configuration so that the bristles  74  generally surround the cutter and extend from the shroud ring  76  to an upper surface of a workpiece WP. As indicated above, it is preferred that the Dust Collector be a centrifugal fan based dust collector and that it serve double duty in the sense that it (I) provides a vacuum source to move chips of material removed from a workpiece from the cutter shroud to the Dust Collector and (II) withdraws air from the plenum  54  in the workpiece hold-down system described above. In this case, the volume of air being withdrawn from the vacuum ports  56  will be greater than the volume of air being drawn through the cutter shroud conduit  70 . Excellent results have been achieved with a Delta centrifugal fan based dust collector system serving double duty as described above. 
     Referring now to  FIG. 4 , the workpiece WP is being held down against the pegs  50  by a reduced pressure condition in the plenum  54  and the cutter  38  has been positioned, relative to the Z direction, at a point where the tip of the cutter  38  is just above the lower foil layer  44 . The cutter  38  is being advanced in the direction of the arrow (in the X direction or the Y direction or both) and a groove  80  is being formed in the work piece WP. The groove  80  is being cut in the foam board  40  and it is defined by two walls that are ninety degrees offset from each other as one would expect from the shape of the cutter blade  38  which comprises two cutting edges that form a ninety degree angle between them. The lower foil layer  44  remains intact below the groove and it can serve as a hinge for the panels on either side of the groove  80 . As pieces of the upper foil layer  42  and the foam board  40  are removed by the cutter  38 , they are drawn into the conduit  70  and conducted to and collected in the Dust Collector. 
     Referring now to  FIG. 5 , the workpiece WP is being held down against the pegs  50  by a reduced pressure condition in the plenum  54  and the cutter  38  has been positioned, relative to the Z direction, at a point where the tip of the cutter  38  is just through the lower foil layer  44 . The cutter  38  is being advanced in the direction of the arrow (in the X direction or the Y direction or both) and a groove cut  82  is being formed in the work piece WP. The lower foil layer  44  is being cut and a groove is being cut into the foam board  40 . This groove cut  82  will separate two pieces of the workpiece WP, one from the other, on either side of the groove cut  82 . As pieces of the foil layers  42  and  44  and pieces of the foam board  40  are removed by the cutter  38 , they are drawn into the conduit  70  and conducted to and collected in the Dust Collector. 
     Referring now to  FIG. 6 , the workpiece WP is being held down against the pegs  50  by a reduced pressure condition in the plenum  54  and the cutter  38  has been positioned, relative to the Z direction, at a point where the tip of the cutter  38  is just a short distance below the upper surface of the foam board  40 . The cutter  38  is being advanced in the direction of the arrow (in the X direction or the Y direction or both) and there is a straight cut channel  84  being formed in the work piece WP. The lower foil layer  44  remains intact and most of the foam board  40  remains intact, too. This straight cut channel  84  demarcates the interface between two pieces which will be separated later and, until they are separated by additional cutting, the straight cut channel  84  maintains the integrity of the workpiece WP so that, for example, the work piece can be loaded into a vehicle, with many other flat workpieces that have been converted according to the present invention, and transported to a job site where the final cutting (and assembly) can be carried out. This will be described further, below, with reference to  FIG. 13 . As pieces of the foil layer  42  and pieces of the foam board  40  are removed by the cutter  38 , they are drawn into the conduit  70  and conducted to the Dust Collector. 
     The apparatus of the present invention is used to create grooves  80  in foam board workpieces, to create groove cuts  82  in foam board workpieces and to create straight cut channels  84  in foam board workpieces. The grooves  80  and groove cuts  82  are especially useful in producing straight sections of duct with square or rectangular cross sections. Referring now to  FIGS. 7 and 8 , material has been removed from a workpiece WP to produce linearly extending grooves  80  and linearly extending groove cuts  82 , all of which are substantially parallel. The bottom B of a finished duct is defined between a groove cut  82  and an adjacent groove  80 . A first side S 1  of the duct is defined between the previously mentioned groove  80  and an adjacent groove  80 . A top T of the duct is defined between the previously mentioned groove  80  and an adjacent groove  80  and the second side S 2  of the duct is defined between the previously mentioned groove  80  and a groove cut  82 . The lower foil layer  44  remains intact in each of the grooves  80  and it acts as a hinge allowing the bottom B to pivot ninety degrees relative to the first side S 1  which, in turn, can pivot ninety degrees relative to the top T, and so on until the two groove cut surfaces at the edge of second side S 2  and the edge of the bottom B will come together to form a duct (not shown) with a rectangular cross section. Construction of the duct can be completed by taping or otherwise securing the bottom B to the second side S 2  in known fashion. 
     Referring now to  FIGS. 9 through 12 , a straight cut channel cutter is indicated generally at  90 . The channel cutter  90  comprises a rotary tool  92  with a chuck  94  in which a side cutting tool  96  is mounted. A guide  98  is supported on the business end of the rotary tool  92  by two flanges  100  so that the side cutting tool  96  extends in a direction that is perpendicular to the bottom surface, shown in  FIG. 10 , of the guide  98 . Extending from the bottom surface of the guide  98  is a first guide ridge  102  which is shaped to be received in a straight cut channel  84 . A second guide ridge  104 , also shaped to be received in a straight cut channel, extends from the bottom surface of the guide  98  on the other side of the side cutting tool  96  from where the first guide ridge  102  is located. In use, the straight cut channel cutter  90  can be positioned with the first guide ridge  102 , the second guide ridge  104 , or both, in a previously cut straight cut channel, with the bottom surface of the guide  98  flat against the upper foil layer  42  or against the upper surface of a workpiece WP. The cutter  90  can then be manipulated along the straight cut channel so that the side cutting tool will cut the workpiece WP forming two walls  106  on either side of the side cutting tool  96 , as shown in  FIG. 12 . The walls will be perpendicular to the upper and lower foil layers  42  and  44  and perpendicular to the upper and lower surfaces of the foam board  40 . 
     Referring now to  FIG. 13 , a workpiece WP that has been processed according to the method of the invention is ready for transportation to a job site. The workpiece WP has been cut to define a first curved side CS 1 , a second curved side CS 2 , a curved top CT and a curved bottom CB. The first and second curved sides CS 1  and CS 2  and the curved top CT and the curved bottom CB each have four sides and two are defined by groove cuts  82  which extend all of the way through the workpiece WP and the other two of which are defined by straight cut channels  84  which extend through one of the foil surfaces and a short distance into the foam board. The portions of the foam board that remain intact in the vicinity of the straight cut channels  84  serve to keep the workpiece WP together in a single flat piece which is especially advantageous for several reasons. The four related duct pieces CS 1 , CS 2 , CB and CT are together and will remain together until they are removed and assembled, for example, at a job site. The flat panel takes up less space than would be taken up if the duct pieces were assembled into the transition duct fitting that they can be assembled into. It will be apparent to those who have utilized KOOLDUCT® that a tool, known as a bender, that is available from the distributors of KOOLDUCT®, would be used to produce gentles bends in the curved top and curved bottom CT and CB before they would be connected to the curved sides CS 1  and CS 2 . The edges of the four pieces formed in the workpiece WP are protected from damage by scrap portions of the workpiece WP that can remain in place until the duct pieces are removed for assembly, for example, at the job site. 
     The workpiece WP shown in  FIG. 13  can be delivered to a job site where a tool such as a straight cut channel cutter  90  can be utilized to cut through the workpiece WP in the locations of the straight cut channels  84 . This will free the four pieces from scrap portions of the workpiece WP and those four pieces should be in excellent shape. The four pieces can then be assembled and installed on site. 
     It will be appreciated that the foregoing description is intended to enable someone of ordinary skill in the field to practice the invention and that the present invention is not limited to the exact details shown but resides as well in the broader aspects and purposes and features described herein.