Abstract:
A process for forming oversized circular pipe has the steps of affixing an elliptically-shaped forming head onto a spiral pipe forming machine, driving a metal strip along the forming head such that the metal strip takes on a shape of the forming head, moving said metal strip out of the forming head into a spiral pattern such that edges of the metal strip engage with each other so as to form an elliptically-shaped spiral pipe, removing the spiral pipe from the forming machine, and forming the elliptically-shaped pipe into a circular shape. The circular pipe has a diameter of greater then forty-eight inches. The forming head has an adjustable diameter.

Description:
RELATED U.S. APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   REFERENCE TO MICROFICHE APPENDIX 
   Not applicable. 
   FIELD OF THE INVENTION 
   The present invention relates to methods and apparatus for formation of circular pipe. More particularly, the present invention relates to those apparatus for the forming of circular pipe in which a spiral metal strip has edges joined to itself so as to define the spiral pipe. More particularly, the present invention relates to methods and apparatus for forming spiral circular pipe having oversized diameters. 
   BACKGROUND OF THE INVENTION 
   Spiral seamed pipes made from strips of sheet metal are widely used to transport fluids. For example, these pipes are frequently used to transport air in order to ventilate, heat and cool buildings. In this application, as well as others, it desired that the pipe produced is strong, lightweight and inexpensive, and provides minimum resistance to fluid flow. The pipe must be sufficiently strong to maintain rigidity over long expanses and against pressure from external forces. Any aberration in the uniformity of the inner pipe surface, such as bends or dents, increases the resistance to fluid flow through the pipe. It is desirable for the pipe to be lightweight so that less manpower is required to carry and install it. 
   In the past various U.S. patents have issued for devices relating to the formation of spiral pipe. U.S. Pat. No. 4,567,742, issued on Feb. 4, 1986 to W. P. H. Castricum, describes a ribbed spiral pipe producing machine. This machine includes conventional elements of a frame, a drive roller for feeding the strip through the frame, a flange roller and folding finger for bending the outer edges of the metal strip, a forming head for forming the strip into a pipe so that the outer edges of the strip mate, and a clenching roller and contra roller for compressing the mated edges to produce a spiral seam. This patented device improves on conventional apparatus by providing only two pairs of edge forming roller assemblies that cooperate to bend the left edge of the strip perpendicular to the strip, and the right edge of the strip into an upward facing, V-shaped channel with its outer edge perpendicular with respect to the stip. 
   U.S. Pat. No. 4,924,684, issued on May 15, 1990 to W. P. H Castricum, describes a apparatus and method for forming and cutting spiral pipe. The pipe forming apparatus includes an enclosed forming head and a mandrel. A continuous strip of metal is driven around the mandrel and inside a lateral bore in the forming head in a helical manner. First and second rollers are mounted in the forming head so as to partially form a spiral lockseam. A third roller is mounted in the upper portion of the forming head so as to close the spiral lockseam. The mandrel is both rotatable and pivotable. 
   U.S. Pat. No. 5,105,639, issued on Apr. 21, 1992 to W. P. H. Castricum, also discloses an apparatus for forming spiral pipe. In particular, this device is configured for forming spiral pipe having a diameter of approximately one inch or less. A continuous strip of metal is driven around the mandrel and inside a lateral bore in the forming head in a helical manner. First and second rollers mounted in the forming head partially form a spiral lockseam. A third roller mounted in the upper portion of the forming head closes the spiral lockseam. Various knives are employed so as to sever the pipe as it rotates. 
   U.S. Pat. No. 5,609,055, issued on Mar. 11, 1997 to W. P. H. Castricum, teaches a method and apparatus for cutting and notching a hollow pipe. This apparatus includes a upper knife assembly having a pipe cutting knife and notch cutting knives with cutting edges adjacent a surface of the pipe and a lower knife assembly having a pipe cutting knife and notch cutting knives with cutting edges adjacent an opposite surface of the pipe. The method of this invention includes stopping the axial and rotational movement of the pipe and moving the lower knife assembly into an overlapping relationship with the upper knife assembly. The notch cutting knives are also moved into cutting position and the axial and rotational pipe movement is resumed. 
   U.S. Pat. No. 5,636,541, issued Jun. 10, 1997 to W. P. H. Castricum, also teaches an apparatus for forming and cutting spiral pipe having a diameter of less than one inch. The device for slitting the spiral pipe into sections includes a first knife that is positioned inside the spiral pipe and a second knife that is positioned outside of the pipe. A support sleeve is also positioned outside of the pipe and is in a fixed radial position with respect to the pipe. The inner and outer knives and the support sleeve move axially with the pipe as the pipe is severed. 
   The conventional spiral pipe forming machine is manufactured by Spiral-Helix, Inc. of Buffalo Grove, Ill. On this device, a forming head is positioned on the machine so as to extend outwardly of a frame portion. Conventionally, the forming head is of a relatively small diameter so that relatively small diameters of ductwork can be formed through the use of such spiral pipe forming process. This ductwork is often used for the passing of ventilation, air conditioning and heating within a building or a very large vehicle. The forming rollers associated with the forming head are positioned adjacent to an outwardly extending frame portion. As such, the maximum diameter of forming head that can be accommodated in such machines must be less than seventy-eight inches in diameter. If the spiral pipe is of oversized diameter, then other techniques are required for the creation of such large diameter ductwork. Conventionally, when such oversized ductwork is required in a particular project, the oversize ductwork is not formed through the use of the spiral-Helix machine, but rather through complicated seam welding processes. In other words, the large circular portion of the ductwork are formed on a roll forming machine. Each of these circular sections is then joined and welded together in end-to-end relationship. This process of forming such oversized circular pipe is extremely expensive, requires a great deal of manpower, and is relatively inefficient. Unfortunately, none of the existing machines have the capability of creating such large diameter spiral pipe. Inevitably, if a forming head of such diameter were utilized on the Spiral-Helix machine, then the edges of the circular forming head would contact the frame portions of the machine and prevent adaptation and use thereof. As such, a need has developed so as to create a forming head by which such large oversize diameter spiral pipes can be formed by using such Spiral-Helix machines. Additionally, there is a need in the art to provide the ability to create such oversize ductwork through the use of a spiral forming process rather than seam welding and roll forming. 
   The requirements to manufacture such large oversize diameter ductwork are particularly important in view of the expanding market for such oversize ducts. Larger athletic facilities are being created throughout the world. These athletic facilities often require the transport of air conditioning and heating to the spectators at the stadiums. As a result, there is a need to transport extremely large volumes of air conditioned or heated air from one location to another within the stadiums and athletic facilities. In other circumstances, larger and larger buildings are being built for manufacturing facilities, entertainment facilities and residential facilities. In view of the size of these large buildings, it is desirable to have such oversized ducts for the transport of large volumes of air from one location to another. Still, and in addition, there is a further requirement to have air conditioning and heating facilities at one location while the requirements of use of such air conditioned or heated air are at a remote location. Once again, there is a need for oversized ducts for the transport of such large volumes of air. There is a need at the present for the creation of such large ductwork through the spiral forming processes associated with previously small diameter ducts. 
   Typically, forming heads used for the creation of such circular pipe are relatively expensive. These forming heads are typically roll formed of steel or aluminum material. The forming heads must be sufficiently strong so as to withstand the forces associated with the formation of the spiral pipe. In certain circumstances, minor adjustments in the diameter of the spiral pipe are necessary after the forming head has been manufactured. If minor adjustments to the diameter of the circular pipe are required, then the previously manufactured forming head must be scrapped and a new forming head created. As such, a need has developed so as to be able to adjust the diameter of the forming head with minimal cost and inconvenience. Additionally, where the forming head is of a relatively large diameter, a need has developed so as to avoid deflections in the large diameter of the forming head. 
   It is an object of the present invention a method and apparatus for the forming of oversized circular pipe which utilizes spiral forming procedures. 
   It is another object of the present invention to provide a method and apparatus for the formation of oversized circular pipe which can utilize the Spiral-Helix machines. 
   It is another object of the present invention to provide a method and apparatus for the formation of spiral pipe which provides the ability to form spiral pipe having a diameters of greater than forty-eight inches without offsetting the forming head. 
   It is another object of the present invention to provide a method and apparatus for the spiral pipe formation of circular pipe which minimizes the costs and labor required for such sections of circular pipe. 
   It is still another object of the present invention to provide a method and apparatus for the formation of circular pipe which allows the forming head to be adjusted between diameters without significantly increasing the cost of the forming head. 
   These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is a process for the forming of oversized circular pipe comprising the steps of: (1) affixing an ecliptically-shaped forming head onto a spiral pipe forming machine; (2) driving a metal strip along the elliptically-shaped forming head such that the metal strip takes on a shape of the forming head; (3) moving the metal strip out of the forming head in a spiral matter such that edges of the metal strip engage with each other so as to form an elliptically-shaped spiral pipe; (4) removing the elliptically-shaped spiral pipe from the spiral pipe forming machine; and (5) forming the elliptically-shaped pipe into a circular pipe. The elliptically-shaped forming head has a shape such that the circular pipe has a diameter of greater than forty-eight inches. 
   The method of the present invention also includes the steps of placing the frame adjacent to the spiral pipe forming machine and positioning rollers on the frame so as to rollably contact the exterior surface of the elliptically-shaped spiral pipe. A cross bar is affixed to cross the elliptically-shaped forming head. A beam is secured in a fixed position relative to the cross bar. The beam is then connected to the cross bar so as to properly support the forming head in a desired vertical orientation. The portion of the forming head having the sharpest curvature is located at the bottom of the forming head. This portion is affixed to the spiral pipe forming machine. A frame portion of the spiral pipe forming machine is spaced away from the portion of the forming head of greatest curvature. In the process of the present invention, a step is required so as to calculate the shape of the forming head such the forming head does not contact and is spaced from this frame portion. 
   The step of forming the elliptically-shaped spiral pipe into the circular pipe includes joining an end of the elliptically-shaped spiral pipe onto an end of a section of the circular pipe. In the process of the present invention, there is also the step of adjusting a diameter of the elliptically-shaped forming head such that the circular pipe is of a desired diameter. This step of adjusting the diameter comprising the steps of: (1) forming a first break on one side of the elliptically-shaped forming head; and (2) placing a first insert element between edges at the first break; and (4) placing a second insert element between the edges at the second break. Additionally, a second break can be formed on an opposite sides of the elliptically-shaped forming. This allows a second insert element between the edges of the second break. Each of the first and second insert elements has an interior surface flush with an interior surface of the elliptically-shaped forming head at the first and second breaks. Specifically, in this step, a first flange is affixed to one edge of the first break and a second flange is affixed on an opposite side of the first break. The first insert element has a third flange extending outwardly therefrom and a fourth flange extending outwardly therefrom in generally parallel relationship to the third flange. The first insert element is positioned between edges of the elliptically-shaped forming head at the first break such that the third flange is juxtaposed against the first flange and such that the fourth flange is juxtaposed against the second flange. The first flange is bolted to the third flange. The second flange is bolted to the fourth flange. 
   The present invention is also a forming head apparatus for forming oversize circular pipe. This forming head apparatus includes an elliptically-shaped body having an exterior surface and an interior surface, and a means for securing the elliptically-shaped body to a circular pipe forming machine such that the body has a sharp curvature at a bottom end thereof and at the forming machine. A frame with rollers is provided with the rollers rotatably mounted thereon. These rollers rotatably contact a surface of the circular pipe. The elliptically-shaped body includes a cross bar affixed thereto and extending thereacross. This cross bar is affixed to a beam extending in parallel relationship thereto. The beam is anchored to an exterior surface. The beam is not necessary, but it helps to stabilize the forming process. 
   In one form of the forming head apparatus of the present invention, there is formed a first break on one side thereof and a second break on an opposite side thereof. A first insert element is removably positioned between the edges of the body at the first break. A second insert element is removably positioned between the edges of the body at the second break. The body has a first flange extending outwardly of the exterior surface adjacent to one of the edges of the first break and a second flange extending outwardly of the exterior surface adjacent another of the edges of the first break. A third flange is affixed to the first insert element at a top thereof. A fourth flange is affixed to the first insert element at a bottom thereof. The third flange is secured to the first flange on the body. The fourth flange is secured to the second flange on the body such that an interior surface of the first insert element is flush with the interior surface of the body. A similar structure is associated with the second break and the second insert element. The first and third flanges have at least one bolt extending therethrough and secured thereto. The second and fourth flanges also have at least one bolt extending therethrough and secured thereto. 
   In the apparatus of the present invention, a metal strip extends along the interior surface of the forming head and extends outwardly therefrom in the form of an elliptically-shaped spiral pipe. This spiral pipe will have a diameter of greater than forty-eight inches. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a side elevational view showing the method and apparatus for the formation of circular pipe in accordance with the teachings of the present invention. 
       FIG. 2  is a perspective view showing the elliptically-shaped forming head in accordance with the teachings of the present invention. 
       FIG. 3  is a side elevational view showing how an elliptically-shaped spiral pipe can be joined to another pipe section so as to form a circular pipe. 
       FIG. 4  is a end view showing an alternative embodiment of the circular pipe forming head of the present invention 
       FIG. 5  is a partial side elevational view of the insert structure associated with the alternative embodiment of  FIG. 4 . 
       FIG. 6  is a detailed isolated end view showing the insert structure associated with the alternative embodiment of  FIG. 4 . 
       FIG. 7  is an isolated view showing the elliptically-shaped forming head of  FIG. 4  without the insert element secured thereto. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , there is shown the apparatus  10  of the present invention for forming an oversize circular pipe. The apparatus includes spiral pipe forming machine  12  along with the elliptically-shaped forming head  14 . The elliptically-shaped forming head  14  has a bottom end  16  of sharpest curvature supported on the bed  18  of the forming machine  12 . A frame structure  20  extends upwardly from the floor upon which the machine  12  rests. Frame structure  20  includes several rollers  22  that are positioned in various locations so as to ride against the exterior surface of the circular pipe produced by the apparatus  10 . A cross bar  24  extends across the narrow diameter portion of the elliptically-shaped forming head  14  so as to maintain the structural integrity of the forming head. A beam  26  is secured to an external structure, or is secured to frame  20 , if required. Struts  28  serve to connect the cross bar  24  to the beam  26  and to maintain the structural integrity of the ellipse formed by the elliptically-shaped forming head  14 . 
   The machine  12  is a conventional spiral pipe forming machine such as those manufactured by Spiral-Helix, Inc. of Buffalo Grove, Ill. This spiral pipe forming machine  12  includes a frame  30  and a control cabinet  32 . A plurality of control knobs, gauges and dials  34  are located on the control panel  36  for controlling and monitoring the operation of the machine  12 . 
   A roller housing  38  is mounted on the frame  30 . The roller housing  38  contains a plurality of rollers which bend the edges of the metal strip  40  in predetermined shapes for forming a lockseam, and which may form corrugation grooves and stiffening ribs in the metal strip  40 . An upper drive roller  42  and a lower drive roller  44  are rotatably mounted within the frame  30  adjacent to the roller housing  38 . The upper drive roller  42  pulls the continuous metal strip  40  into the frame  30  through the roller housing  38 , and over the lower drive roller  44 . The drive rollers then cooperate to push the metal strip  15  between the upper guide plate  46  and the lower guide plate  48  into the forming head  14 . 
   The forming head  14  curls the metal strip in a helical manner so that the outer pre-formed edges of the strip  40  are adjacent to each other and mesh therewith. The helically-curled strip thus takes the shape of a spiral cylinder. The adjacent, mated edges of the strip are then compressed between a support roller and a clenching roller so as to form a proper lock seam. The metal strip  40  is continuously pushed by the drive rollers  42  and  44  through the forming head  14 , in spiral manner, so that the spiral pipe is continuously produced with a spiral lockseam. 
   As the spiral pipe is formed, it will move out of the forming head  14  in a spiral manner. That is, the pipe and its leading edge will simultaneously rotate and move forward in the axial direction of the pipe. The pipe will be continuously produced until its reaches its desired length. At that point, a pipe cutting and notching apparatus will notch and sever the pipe into a section. 
   Importantly, in  FIG. 1 , it can be seen that the frame  30  includes a frame portion  50  that is positioned adjacent to the periphery of the forming head  14 . This frame portion  50  is essential for the proper positioning of the drive rollers  42  and  44 . The drive rollers  42  and  44  push the metal strip  40  between the upper guide plate  46  and the lower guide plate  48  and into the support arm  52 . Support arm  52  pushes down on the support roller and holds it in place. As such, the metal strip  40  will start to follow a path along the interior surface  54  of the elliptically-shaped forming head  14 . As a result, the elliptically-shaped forming head  14  will create an elliptically-shaped spiral pipe, rather than the circular-shaped pipe of the prior art. 
   As can be seen, the location of the frame portion  50  would create a obstruction relative to the support arm  52  and the location of the elliptically-shaped forming head  14  if the elliptically-shaped forming head  14  were of a circular configuration. The frame  50  creates an inherent barrier to the expansion of duct diameters beyond forty-eight inches in diameter. If the forming head  14  were circular, then extensions would have to be formed outwardly of the machine  12  in an inconvenient and unreliable manner. So as to accommodate the location of the frame  50 , the elliptically-shaped forming head  14  is positioned so that the sharp curvature of the forming head  14  is located at the support arm  52  and on the bed of the machine  12 . As a result, the sides adjacent to the frame portion  50  can extend upwardly therefrom in generally spaced relationship and non-interfering relationship with frame portion  50 . The support frame  20  will maintain the elliptically-shaped forming head  14  in its desired orientation above the machine  12 . As a result of the structure of the present invention, it is now possible to form circular pipe having diameters of greater than forty-eight inches. In order to determine the proper ellipse for the elliptically-shaped forming head  14 , it is first necessary to understand the desired diameter of the ultimate circular pipe. Once the desired diameter is determined, then it is necessary to know the spacing between the support arm  20  and the frame portion  50 . As a result, a properly shaped ellipse of the elliptically-shaped forming head  14  can be calculated. As an example, if the ultimate diameter of the circular pipe is 100 inches then the elliptically-shaped forming head  14  will have a narrow diameter of 85 inches and a wide diameter of 114 inches. 
     FIG. 2  is an isolated view showing the elliptically-shaped forming head  14  of the present invention. The forming head  14  is formed of a steel material having a proper ellipse for the purposes of installation on the machine  12 . The bottom end  16  of the elliptically-shaped forming head  14  should be positioned under the support arm  52 . As a result, a suitable slotted area  60  should be formed at the bottom  16  so as to allow the metal strip  40  to be introduced thereinto. The metal strip  40  is free to be driven along the interior surface  54  in a continuous and spiral manner. The exterior surface  62  can be supported by the frame structures described hereinbefore. 
   After the machine  12  has driven the metal strip  40  through the interior of the elliptically-shaped forming head, a length of elliptically-shaped spiral pipe will be formed. However, it is important consideration of the present invention that the ultimate goal is to produce a section of circular pipe of constant diameter. As such, the elliptically-shaped spiral pipe will need to be converted into circular pipe.  FIG. 3  shows the manner in which this conversion can occur. As can be seen in  FIG. 3 , a first section  70  of spiral pipe has been positioned in a desired location. This first section  70  is of a circular configuration. The second section  72  illustrates the spiral pipe as formed by the process  10  of the present invention. Spiral pipe  72  will initially be of elliptical form. However, within the concept of the present invention, it is easy to form the elliptically-shaped spiral pipe section  72  into a circular pipe section by simply securing the end  74  of section  72  to the end  76  of section  70 . Since the pipe section  72  is elliptically shaped, it can be easily manipulated, maneuvered and adjusted so as to conform with the edge of the circular spiral pipe  70 . After connecting the end  74  to the end  76  by various means, such as welding, tapping, adhesive, sealants, or other means, the second pipe section  72  will have its desired circular configuration. Within the concept of the present invention, although the ultimate result of the use of the elliptically-shaped forming head  14  is the creation of elliptically-shaped spiral pipe, the spiral pipe is of a configuration that can be easily manipulated for movement and configuration into a circular design of constant diameter. Fixtures and other supports can be employed so as to maintain the circular orientation of the elliptically-shaped section  72  during its installation onto the circular section  70 . 
     FIG. 4  shows an alternative embodiment of the elliptically-shaped forming head  80  of the present invention. Forming head  80  has an elliptically-shaped configuration as in the previous embodiment of the forming head  14 . However, a first break  82  is formed on one side of the forming head  80  and a second break  84  is formed on an opposite side of the forming head  80 . These breaks  84  and  82  are cuts through the wall thickness of the forming head  80 . The breaks  82  and  84  are particularly configured so that the forming head  80  can be manipulated for size adjustments and for producing spiral pipe of different diameters. In  FIG. 4 , it can be seen that an insert element  86  has been positioned between the edges of the break  82 . Similarly, another insert element  88  has been positioned between the edges  84 . As a result, the wide diameter of the elliptically-shaped forming head  80  is greater by a function of the length of the insert elements  86  and  88 . Generally, each of the insert elements  86  and  88  has a U-shaped configuration in which the inner surface  90  of the insert element  86  is flush with the interior surface  92  of the forming head  80 . Similarly, the inner surface  94  of the insert  88  is flush with the interior surface  92  of the forming head  80 . As a result, there will be no interruption or obstruction of the travel of the metal strip during the formation of the elliptically-shaped spiral pipe. As will be described hereinafter, when the insert elements  86  and  88  are removed, the breaks  82  and  84  will be closed such that the interior surface  92  of forming head  80  is contiguous and flush with itself. 
     FIG. 6  illustrates the configuration of the insert element  86  as positioned on the forming head  80 . The insert element  86  is positioned in the area of the break  82 . As can be seen in  FIG. 5 , break  82  will have a first edge  100  and a second edge  102 . A first flange  104  extends outwardly of the exterior surface  106  of the forming head  80  at break  100 . A second flange  108  extends outwardly of the exterior surface  106  of the forming head  80  at break  102 . Importantly, the first insert element  86  includes a third flange  110  positioned in juxtaposition against an interior surface of the first flange  104 . The insert element  86  also includes a fourth flange  112  which is positioned in juxtaposition against an inside surface of the second flange  108 . Bolts  114  serve to secure the first flange  104  to the second flange  110 . Similarly, bolts  116  are used to secure the second flange  108  to the fourth flange  112 . As a result, the insert element  86  will fill in the space between the edges  100  and  102  of break  82 . A similar structure, such as that shown in  FIG. 5 , is employed in association with the second break  84  and the second insert element  88  on the other side of the forming head  80 . 
   In  FIG. 6 , it can be seen how the first insert element  86  is positioned between the first flange  104  and the second flange  108 . Insert element  86  has a surface  120  positioned between the edge  100  and the edge  102  of break  82 . The inner surface  90  will be flush with the inner surface  92  of the forming head  80 . The insert element  86  also shows the third flange  110  and the fourth flange  112 . The bolts  114  join the first flange  104  to the third flange  110  in surface-to-surface relationship. Similarly, bolts  116  join the second flange  108  to the fourth flange  112  in surface-to-surface relationship. Suitable bolt holes are formed through each of the flanges  104 ,  108 ,  110  and  112  so that proper alignment of the surfaces  90  and  92  can be achieved. 
   In  FIG. 7 , it can be seen how the insert element  86  has been removed. As a result, the break  82  is closed so that the edges  100  and  102  are in juxtaposition. The inside surface  92  of the forming head  80  will be continuous and flush. The first flange  104  is joined the second flange  108  through the use of bolts  122 . Removal of the insert element  86  will cause the maximum diameter of the elliptically-shaped forming head  80  to be reduced in size. If it is necessary to make minor adjustments in the diameter in the forming head  80 , then the insert elements  86  and  88  can be suitably employed. As a result, the present invention eliminates the need for constantly scrapping, reforming or otherwise taking other expensive measures for the remedying of diameter discrepancies in the elliptically-shaped spiral pipe. 
   The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction or in the steps of the describesd method can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.