Abstract:
A pipe manufacturing device and method provides for pipe diameter monitoring and responsive pipe diameter control. Various pipe configurations and pipe assemblies adapted for ease of in the field connection are also provided.

Description:
TECHNICAL FIELD  
       [0001]     This application relates generally to helically corrugated metal pipe commonly used in drainage applications and, more specifically, to a method of producing such pipe with improved diameter control and/or end connection features.  
       BACKGROUND  
       [0002]     The standard production process for producing helically corrugated metal pipe is well known and involves first forming lengthwise corrugations in an elongated strip of sheet metal, with the corrugations extending along the length of the strip. The corrugated strip is then spiraled into a helical form so that opposite edges of the corrugated strip come together and can be either crimped or welded to form a helical lock along the pipe. Diameter control of the resulting pipe is regularly an issue in the manufacturing process and is important to the functionality of the pipe from an installation standpoint when pipes are being connected end to end at a job site in the field. Attempts to address diameter control have been made in the past. U.S. Pat. Nos. 3,940,962, 3,417,587, 4,287,739 and 4,438,643 describe pipe manufacturing techniques and related equipment. Improvements are continually sought.  
         [0003]     Joining lengths of helically corrugated metal pipe creates issues in the field. U.S. Pat. No. 5,842,727 teaches a coupling member that can be used to join the ends of two pipes in a sealed manner. Improvements in the area of pipe coupling would be advantageous as the same could reduce pipe installation costs.  
       SUMMARY  
       [0004]     A system and method for pipe size or diameter control in connection with the production if helically corrugated pipe is provided. Advantageous pipe configurations may be achieved. Pipe size monitoring and control may be automated. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a top plan schematic of a pipe manufacturing device;  
         [0006]      FIG. 2  is a cross-section of an exemplary corrugated metal strip taken along line  2 - 2  of  FIG. 1 ;  
         [0007]      FIG. 3  is an exemplary cross-section of a lockseam;  
         [0008]      FIG. 4  is an exemplary control system configuration for the device of  FIG. 1 ;  
         [0009]      FIG. 5  shows exemplary pipe with unitary bell end and unitary spigot end;  
         [0010]      FIG. 6  shows a spigot end of one pipe within a bell end of another pipe;  
         [0011]      FIG. 7  depicts exemplary pipe diameter profiles;  
         [0012]      FIGS. 8 and 9  illustrate an exemplary pressure roller and drive assembly;  
         [0013]      FIG. 10  illustrates an exemplary pipe diameter monitoring device;  
         [0014]      FIG. 11  is a schematic illustration showing a pair of lockseam rollers and a pressure roller;  
         [0015]      FIG. 12  is a schematic depiction of a pipe having a larger diameter end and a smaller diameter end; and  
         [0016]      FIG. 13  is a schematic depiction of another embodiment of a pipe assembly. 
     
    
     DETAILED DESCRIPTION  
       [0017]     Referring to  FIG. 1 , a pipe manufacturing line or device  10  is shown in top plan schematic form. The device  10  includes a decoiler unit  12  for receiving a coil  14  formed by a rolled metal sheet. The illustrated decoiler unit  12  supports the coil  14  on a rotatable expansion mandrel  16 , permitting the coil to rotate during pipe manufacture. A weld table  18  is shown downstream of the decoiler unit  12  and is provided for welding the end of one metal sheet to the end of the metal sheet of a different coil upon coil replacement. A corrugating line  20  includes a number of corrugators  22  for drawing the metal sheet off of the coil  14  and placing corrugations in the metal sheet to produce a corrugated metal strip  24 . The metal sheet passes between upper and lower corrugating rollers in each of the corrugators  22  and the rollers apply pressure to the sheet to form corrugations. By way of example, first corrugator  22  may form a middle corrugation in the strip, next corrugator  22  may form second and third corrugations alongside the previously formed middle corrugation, next corrugator  22  may form fourth and fifth corrugations alongside the previously formed second and third corrugations, and so on, with the number of corrugators varying as necessary. However, variations on the operation of the corrugators are possible. The corrugations may be of any suitable shape and configuration. In one embodiment, the pipe manufacturing device operates to produce hydraulically efficient pipe such as that described in U.S. Pat. No. 4,838,317, in which case the corrugated metal strip may have a cross-section similar to that generally shown in  FIG. 2 , where the corrugations  11  are shown with a generally rectangular or box-shape and the side edges of the corrugate metal strip  24  includes respective lips  13  and  15  for use in producing the helical lockseam described below. The exact configuration of locking lips  13  and  15  can vary.  
         [0018]     The rollers of the illustrated corrugators  22  are driven by an electric motor  26  with its output linked to a gearbox/transmission arrangement  28 . A forming head  30  is positioned to receive the corrugated metal strip  24  and includes a lockseam mechanism  32  located at a pipe exit side  34  of the forming head. The forming head  30  may be a well known three-roll forming head configured to spiral the corrugated metal strip  24 . The lockseam mechanism  32  locks adjacent edges of the spiraled corrugated metal strip in a crimped manner to produce a helical lockseam  100  in the resulting pipe  102 . Specifically, as the corrugated metal strip is helically curved back upon itself to form the pipe-shape, the locking lips  13  and  15  come together before passing into the lockseam mechanism  32 , and the lockseam mechanism  32  presses the lips together to produce a lockseam that may, in one example, have the general appearance of that shown in the cross-section of  FIG. 3 . Referring to  FIG. 11 , in one embodiment the lockseam mechanism  32  is formed by an upper lockseam roller  104  and a lower lockseam roller  106 . The engaged locking lips  13  and  15  of the spiraled strip pass between these rollers where the crimping operation is performed. As an alternative to the lockseam mechanism, a weldseam mechanism could be provided to join adjacent edges of the strip to form a helical weldseam.  
         [0019]     Referring back to  FIG. 1 , a saw unit  36  is positioned along the pipe exit path and includes a saw  38  that is movable into and out of engagement with the pipe  102  and that is also movable along a path parallel to the pipe exit path so that the pipe can be cut even while pipe continues to be produced. Pipes with a variety of diameters can be formed by the device  10 , and large scale diameter control is made by adjusting an entry angle of the corrugated metal strip  24  to the forming head  30 . Such angle adjustment can be achieved by either by rotating the forming head  30  relative to a stationary corrugation line  20  or by rotating the corrugation line  22 , weld table  18  and decoiler unit  12  relative to a stationary forming head  30 . A variety of systems such as that generally described above have long been used and are available from, for example, Pacific Roller Die of Hayward, Calif. and IMW Industries of Chilliwack, British Columbia, Canada.  
         [0020]     The pipe manufacturing device  10  also includes a pipe size monitoring device  40  along the pipe exit path, in this case shown downstream of the saw unit  36 . However, the pipe size monitoring device  40  could also be located upstream of the saw unit  36 . While helically corrugated pipe is generally specified, along with other parameters, by length and diameter, the term “diameter” can be difficult to apply to the pipe with absolute technical accuracy because the pipe may actually be slightly out of round. The term “pipe size” is used herein to broadly refer to any of a perimeter (inner or outer) dimension of the of the pipe, a diameter dimension of the pipe, or some other dimension of the pipe that is reflective of the flow capacity of the pipe, but the term “pipe size” specifically does not include pipe length. As used herein the term “diameter” applies even to pipe that may be out of round, in which case the diameter may be an average radial dimension measured from a generally centrally located axis of the pipe.  
         [0021]     The pipe size monitoring device  40  can be used to provide automated pipe size control for pipe  102  as it is produced. Specifically, the device  10  may include an internal pressure roller  50  located downstream ( FIG. 1 ) and slightly offset laterally of the lockseam rollers  104  and  106  as shown in  FIG. 11 . As demonstrated schematically by  FIG. 11 , the pressure roller  50  is located for rolling contact with an inner surface  110  of the pipe  102 . In one example the pressure roller is positioned such that it rolls over the inner side of one of the box-shaped corrugations  11 . The pressure roller  50  is movable along a vertical path  52  so that the radially outward pressure applied to the inner surface  110  can be varied. Due in part to the relative positioning of the pressure roller  50  between the seaming roll location  51  and the buttress roll location  53  (both of which are part of the forming head), when the pressure roller  50  is moved downward (e.g, to position shown by the dashed line circle) the pressure roller  50  causes the “next coil” of pipe to be pulled into the lockseam slighly faster, or in other words with a slightly tighter or smaller curvature (as reflected in an exaggerated sense by dashed line strip  55 ), causing the pipe size to decrease. On the other hand, when the pressure roller  50  is moved upwards, the next coil of pipe is pulled into the lockseam slightly slower, or in other words with a slightly looser or larger curvature, causing the pipe size to increase. Tightening or decreasing the curvature of the pipe results in an effective increase in the instantaneous helix angle of the pipe and loosening or enlarging the curvature of the pipe results in an effective decrease in the instantaneous helix angle of the pipe.  
         [0022]     Referring now to  FIG. 4 , a schematic representation of an exemplary control system of the pipe manufacturing device  10  is provided. The pipe size monitoring device  40  provides an output  42  that is indicative of the pipe size as the pipe is being produced. The output  42  may vary regularly to reflect pipe size changes as they occur. In one embodiment the output  42  is indicative of pipe size by way of an analog or digital signal that actually contains the pipe size information. In another embodiment the output  42  is indicative of pipe size by reflecting changes from a set point, those changes being convertible to an actual pipe size by suitable processing. Either way, a control unit  44  may receive the output  42  and responsively effect operation of an automated drive mechanism  54  that adjusts the position of the pressure roller  50 . Thus, it is seen that the device  10  provides for automated control of pipe size (e.g., diameter) by providing a feedback arrangement of monitored pipe size. In one example, the pressure roller  50  and related drive  54  may be configured to provide diameter control within a tolerance of about one fourth of one percent (0.25%) or better of total pipe diameter, such as about one sixth of one percent (0.167%) or better of total pipe diameter or about one eighth of one percent (0.125%) or better of total pipe diameter. Thus, it is seen that the device  10  provides advantageous pipe size or diameter control during pipe production.  
         [0023]     In one embodiment the control unit  10  is configured to provide pipe size control of at least two types. Specifically, in a first mode the control unit  44  effects operation of the automated drive  54  so as to maintain a substantially constant pipe size during pipe production (e.g, by comparing a measured pipe size to a desired pipe diameter stored in memory of the control unit and effecting operation of the drive  54  when the measured pipe size moves outside of a certain range about the desired pipe size, or by comparing a monitored pipe size variation to a permissible variation stored in memory and effecting operation of the drive  54  when the monitored pipe size variation exceeds the permissible variation). In a second mode the control unit  44  effects operation of the automated drive  54  so as to intentionally vary pipe size during pipe production (e.g., by comparing the measured pipe size to a desired diameter as indicated by a desired pipe diameter profile stored in memory, or by comparing monitored pipe size variation to a desired variation profiled stored in memory). Selection of either the first mode or the second mode may be made via a user interface associated with the control unit  44 . In one embodiment the user interface may take the form of a touch screen display  46  that displays visual interface keys that an operator can touch and trigger. However, the user interface could also take other forms, such as a standard display in combination with a keypad. In either case, during pipe production the display may  46  provide a continuously updated visual display of measured pipe size or diameter and/or of variance of pipe size or effective diameter from a desired pipe size.  
         [0024]     In one example of the above-mentioned second mode, pipe production is controlled so that a resulting pipe has one end with a larger diameter than its opposite end. Referring to  FIG. 12  where the profile of such a pipe is shown schematically, a helix angle α 1  toward larger diameter end  300  is larger than a helix angle α 2  toward smaller diameter end  302 , where the helix angle is taken at instantaneous locations along the lockseam and is reference from a central pipe axis  304 . It may be difficult to observe the helix angle difference between opposite pipe ends where the pipe size is large and the diameter difference between the two ends of the pipe is only a couple of inches or less.  
         [0025]     The pipe, with ends of different diameters, can then be worked further to produce a pipe configuration with advantageous bell and spigot connecting ends. Specifically, the larger diameter end of the pipe may be worked so as to produce a substantially corrugation free bell end  120  and the downstream end is worked to produce a spigot end  122 , as shown in  FIG. 5  where the bell end  120  and spigot end  122  are shown facing each other for ease of relative discussion. The bell end  120  includes an outwardly flared entry lip  124  at the end edge of generally cylindrical portion  126 . At the opposite end edge of generally cylindrical portion  126  one or more annular corrugations  128  are also formed. The spigot end  122  is formed with one or more annular corrugations so as to provide an annular gasket seat  130 . Notably the very edge of the spigot end  122  flares outwardly. The inner diameter D 1  of the bell end  120  is slightly larger than the outer diameter D 2  of the spigot end  122 , enabling the spigot end  122  of one pipe to be readily inserted into the bell end  120  of another pipe as reflected in  FIG. 6 . In one example, the inside diameter D 1  of the bell end is at least about ⅓″ greater than the outside diameter D 2  of the spigot end  122 . In another example, D 1  is at least about ½″ greater than D 2 . Variations are possible. Also shown is a gasket  132  positioned in gasket seat  130  so as to seal with the inside surface of bell end portion  126 . The internal portion of annular corrugation  128  provided adjacent the cylindrical portion  126  of bell end  120  serves as an abutment or stop that contacts the outwardly flared spigot end  122  so that entry of the spigot end into the bell end  120  is limited.  
         [0026]     In one example, an axial length of cylindrical portion  126  is at least about four inches, while in another example an axial length of portion  126  is at least about six inches. Variations are possible.  
         [0027]     The working of the end of the pipe to form the spigot end may be achieved using a suitably formed recorrugator, which is a device known in the art. Likewise, the working of the end of the pipe to form the bell end may start by using a recorrugator to form annular corrugations at the pipe end. The resulting annular corrugations at the very end of the pipe are then eliminated to form cylindrical portion  126  by a similar rerolling process. Alternatively, one or more annular corrugations may be formed in position slightly spaced apart from the end of the pipe and the remaining helical corrugations at the end of the pipe may be eliminated by rerolling to form cylindrical portion  126 .  
         [0028]     The device  10  can be used in a process to form multiple helically corrugated metal pipe segments of similar length that are readily connectable end to end. Specifically, the method involves: (a) drawing a metal sheet off of a coil; (b) corrugating the metal sheet to produce a corrugated metal strip; spiraling the corrugated metal strip and locking adjacent edges of the spiraled corrugated metal strip in a crimped manner to produce a helical lockseam; (d) automatically monitoring pipe size of pipe being produced; (e) based upon the pipe size monitoring, automatically varying helix angle of the pipe as it is produced in a manner to intentionally vary pipe diameter; (f) producing multiple pipe segments by cutting the helically corrugated metal pipe each time a specified length of pipe is produced; (g) coordinating the pipe diameter variations of step (e) with the cutting operations of step (f) such that pipe segments are produced in the following sequence in a repeating manner: (1) producing a pipe segment having a downstream end and an upstream end, a diameter of the upstream end larger than a diameter of the downstream end, then (2) producing a pipe segment having a downstream end and an upstream end, a diameter of the upstream end smaller than a diameter of the downstream end. As a general rule the diameter of the upstream end of each pipe segment of (g)(1) will be substantially the same as the diameter of the downstream end of each pipe segment of (g)(2). For each pipe segment of (g)(1), the upstream end is rerolled or otherwise worked to produce a substantially corrugation free bell end, and the downstream end is rerolled or otherwise worked to produce a spigot end with at least one annular corrugation. For each pipe segment of (g)(2), the downstream end is rerolled or otherwise worked to produce a substantially corrugation free bell end, and the upstream end is rerolled or otherwise worked to produce a spigot end with at least one annular corrugation.  
         [0029]     The diameter control from end to end of each pipe segment may be in accordance with a diameter profile stored in memory of the control unit. Two exemplary diameter profiles are shown in  FIG. 7 . In profile  150  the pipe diameter is controlled in a substantially linear manner between diameters D A  and D B , with the pipe being cut at points  152  along the profile. In profile  154  the pipe diameter is controlled so that the diameter is temporarily held stable, at either diameter D C  or D D , before and after each of the cut points  152 . Other profiles could also be developed and used without departing from the scope of this application.  
         [0030]     Referring now to  FIGS. 8 and 9 , an exemplary pressure roller assembly and associated automated drive  54  are shown. Pressure roller  50  is rotatably held between end brackets  160  and  162  that extend from a support assembly  164 . Support assembly  164  includes at least two members threadedly engaging each other, where one of the members is rotatable but has a fixed position along vertical axis  166  and the other member is non-rotating but is movable along axis  166 . A servomotor  168  is provided to effect rotation of the rotatable member via a chain and sprocket arrangement or a belt and pulley arrangement  170 . The smaller pulley/sprocket  172  transfers the rotation to a larger pulley/sprocket  174  to effect rotation of the rotatable member of support assembly  164 . The size and pitch of the threads of the support assembly members, the relative size of the pulleys/sprockets  172  and  174  and the precision of the servomotor  168  can be selected to provide a desired level of controllability and tolerance for position of the pressure roller  50 . The entire pressure roller assembly can be supported off of the end of the pipe forming head  30  ( FIG. 1 ) so as to be located internal of the pipe as it is produced.  
         [0031]     Referring now to  FIG. 10 , an exemplary pipe size monitoring device  40  is shown and includes steel frame with a base  180  and upright side supports  182  and  184 . Atop support  182  is a ring member  185  and atop support  184  is a rotatable pulley  186  supported on axis  190 . A tension line  192  (such as a wire, band or rope) has one end fixed to the ring  185  and loops about the pipe that moves along the pipe exit path. The tension wire  192  extends to pulley  186  and is fixed for rotation with the pulley  186  by a wire locking screw  194 . A tensioning arm  196  is pivotably connected with the pulley  186  at axis  198  and is also pivotably connected at a non-moving location  200  along an upright guide bar  202 . A linear transducer  204  includes one end  206  pivotably connected with the tensioning arm  196  and its opposite end  208  pivotably connected to a horizontal support  210 . A spring member  212  extends between the tensioning arm  196  and the horizontal support  210  to bias the pulley  186  in the counterclockwise direction reflected by arrow  214 . A wire source  215 , such as a wire spool, is also shown. During pipe manufacture, increases in the diameter of the pipe are translated into rotation of the pulley  186  in the clockwise direction of the pulley  186  as reflected by arrow  216 , resulting in an extension of the linear transducer  204 . Conversely, decreases in the diameter of the pipe are translated into rotation of the pulley  186  in the counterclockwise direction of the pulley  186  as reflected by arrow  214 , resulting in a retraction or shortening of the linear transducer  204 . The linear transducer  204  outputs an electrical signal that varies with its length. Thus, pipe diameter variations are reflected by signal changes from the transducer  204 , that can be provided to the above-mentioned control unit  44  ( FIG. 4 ). When it is desired to change from measuring a relatively small diameter pipe to a relatively large diameter pipe, the wire locking screw  194  is released to allow sufficient wire or other line to feed past the pulley  186  for extending about the larger pipe diameter, and the wire locking screw  194  is again rotated to lock the wire in place for movement with the pulley  186 . Other types of pipe size monitoring devices could also be used. As used herein “diameter variations” or “pipe size variations” can be reflected in a signal that contains an absolute diameter or pipe size measurement or in a signal that simply departs from a reference level.  
         [0032]     It is recognized that the position of the pressure roller  50  could also be controlled by operator (e.g., by pushing an up or down button or by rotating a knob) in response to an indication on the operator display indicating that pipe diameter is moving or has moved out of tolerance.  
         [0033]     Referring now to  FIG. 13A , one end of a helically corrugated pipe  400  is shown with a bell end fitting  402  attached thereto. The end of the pipe  400  is rerolled to eliminate the helical corrugations but to leave at least one annular gasket seat  404  into which an annular gasket  406  is placed. The annular gasket  404  might alternatively be located in the annular corrugation  405  located closer to the end of the pipe. One end  408  of the bell fitting  402  is configured to slide onto the end of the pipe  400  and to engage the gasket  406 . In the illustrated embodiment fitting end  408  include an outwardly turned lip or flange. The bell fitting  402  is held on the end of the pipe by a shrink wrap material, the position of which prior to heat shrinking is shown by solid line  410  and the position of which after heat shrinking is shown by dashed line  412 . This pipe assembly can be produced in the plant so as to avoid the need to deal with heating the shrink wrap in the field. Specifically, the helically corrugated pipe  400  is produced and it end is rerolled to form the annular gasket seat  404 . The annular gasket  406  is then positioned in the seat. The bell fitting  402  is typically manufactured with a diameter to assure it can readily slide onto the end of the pipe  400 , but not so large as to have excessive play relative to the end of the pipe. Once the bell fitting is slid onto the end of the pipe into the desired position relative to the gasket  406 , the shrink wrap is wrapped around the pipe as generally shown at  410 . Next, the pipe assembly can be passed by a suitable hot air heating system to cause the shrink wrap to shrink, thereby securely holding the bell fitting on the end of the pipe and assuring a good seal. In some embodiments is may be possible to eliminate the gasket  406  and to rely upon shrink wrap material alone to form a suitable seal, particularly where the shrink wrap material is positioned so as to shrink tightly over at least one annular corrugation crest or other annular formed ring on each of the pipe end and the bell fitting end.  
         [0034]     The opposite end of the pipe  400  may be configured to be a spigot end as generally shown in  FIG. 13B , with the end rerolled to provide an annular gasket seat  420 . In the field, as pipes are being connected end to end, a gasket  422  is placed in the gasket seat  420  of the spigot end of one pipe and the spigot end is then pushed into the bell end (formed by the bell fitting) of the other pipe. The gasket  420  forms a suitable seal between the spigot end and bell end. The bell fitting may include an inwardly extending lip or corrugation  424  against which the end face  426  of the spigot end of a pipe will abut, providing a simple manner of assuring that spigot ends are inserted into bell ends properly.  
         [0035]     It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. Accordingly, other embodiments are contemplated.