Background Art Round, thin-walled spiral seamed metal ducts made from a continuous strip of sheet metal are widely employed in heating and air conditioning installations, as well as in other air ducting installations. Spiral duct has a number of advantages, in both ease of installation and performance.

One commercially available machine for producing such spiral duct is known as a Tubeformer machine, manufactured by Spiral-Helix, Inc. of Buffalo Grove, Illinois, and described for example in Castricum U. S. Pat.

Nos. 4,567,742; 4,706,481 and 4,711,110.

In a Tubeformer machine, the metal strip of stock material is continuously fed into the machine to continuously produce spiral seamed pipe. The strip first passes through a series of flange forming rollers which bend the edges into predetermined profiles suitable for forming a lockseam. Parallel corrugations or reinforcing ribs may also be formed. The strip then enters at an angle and engages the inner surface of a drum-like forming head or mandrel. The forming head or mandrel curls the metal strip in a helical manner, bringing opposite edges of the strip adjacent to each other, defining and fixing the diameter of the spiral metal pipe produced. The profiles of the adjacent edges engage each other, and are then compressed to form a spiral lockseam. The spiral metal pipe produced extends diametrically generally upwardly with reference to the table-like base of the machine.

Significant frictional forces are involved as the strip enters and engages the inner surface of the forming head or mandrel. Accordingly, the forming head or mandrel must be sufficiently robust to withstand the forces involved. In addition, lubricant is employed as the metal strip passes into and around the inside of the forming head or mandrel. This requires a lubricant supply system, which adds to the complexity of the machine. In addition, a significant amount of lubricant remains on the surface of the spiral seamed pipe after it has been produced, making the pipe somewhat messy to handle. Thus, quantities of lubricant typically remain on a floor surface where spiral seamed metal pipe manufactured by a Tubeformer machine has been placed.

A different forming head or mandrel must be provided for each diameter of spiral pipe to be produced, adding to the cost of the machine, and requiring storage space for a set of relatively large mandrels. Setup can be time-consuming.

Another machine for producing spiral seamed hollow pipes is disclosed in Hale et al U. S. Pat.

No. 3,132,616. The Hale et al machine also employs a drum-like mandrel, but differs from the Spiral-Helix Tubeformer machines in that the metal strip passes around the outside of the mandrel. A forming device causes the metal strip to bend around the mandrel, and seams adjacent edges. A similar principle is employed in"Sprioflex Tubeformer"machines, manufactured by Drossbach GmbH & Co.

KG, Max-Drossbac-StraGe 7, D-86639 Rain/Lech, Germany, available in the United States through Ovalformer LLC, 45 Loop Road, P. O. Box 793, Arden, North Carolina 28704. In the Hale et al and Spiroflex Tubeformer machines, the spiral metal pipe being produced extends diametrically generally downwardly, necessitating the provision of sufficient clearance space above a floor surface.

The Spiral-Helix Tubeformer machines and the Spiroflex Tubeformer machines produce round spiral duct.

There are, however, installations where limited space prevents the use of round spiral duct, and where, accordingly, flatter duct which is rectangular or oval in cross section is employed. (Oval duct is also known in the art as"flat-oval,"and the terms"oval"and"flat- oval"are employed interchangeably herein.) Accordingly, a separate machine, known as an ovalizer, is ordinarily employed to form round duct to oval.

Spiral-Helix, Inc. also manufactures ovalizers, two models of which are known as"The Helix Ovalizer 36/12"and"The Compact Helix Ovalizer 24/6."Another ovalizer, manufactured by Ovalformer LLC, is disclosed in Price et al U. S. Pat. No. 6,000,260.

Disclosure of Invention Accordingly, it is seen to be desirable to provide a compact machine for producing spiral metal pipe, which machine minimizes the use of lubricant, is readily adjustable to form spiral metal pipe of different diameters, is relatively low in cost to manufacture, and is relatively simple to set up and operate.

It is also seen to be desirable to provide a machine which directly produces flat oval spiral seamed duct work, without requiring a separate ovalizer machine.

In an exemplary embodiment, a machine for producing spiral seamed hollow pipe includes a bending roller station wherein a metal strip is formed into a helix using rolling contact. This minimizes frictional forces and the attendant need for lubrication, and eliminates the need for a forming head or mandrel (although a stabilization hoop may optionally be employed). The strip is driven through the bending roller station wherein the metal strip is continuously bent on a bending line which is parallel to the central axis of the spiral pipe being produced and which extends generally across the metal strip but at an angle offset from a right angle with reference to the outer edges of the metal strip

as the metal strip enters the bending roller station. The offset angle is determined based on the width of the strip and the diameter of spiral pipe produced.

Within the bending roller station, rather than individual bending rollers extending all the way across the strip, there are a plurality of rollers organized as what may be viewed as staggered roller segments. Upstream or pinch rollers contact the metal strip on the bending line (which is offset from a right angle with reference to the metal strip). At the same time, the rotational axes of the rollers are perpendicular to the metal strip.

Accordingly, the metal strip rolls freely past the bending rollers without undue friction, and yet. does not"walk" off the bending roller sets.

The bending roller station thus includes a plurality of bending roller sets. The bending roller sets are positioned generally side-by-side generally in respective roller set planes which are parallel to each other and to the edges of the metal strip as the metal strip enters the bending roller station, and perpendicular to the metal strip as the metal strip enters the bending roller station. Each of the bending roller sets includes an inside roller, an outside upstream roller cooperating with the inside roller to define a pinch roller pair, and an outside downstream roller. Each of the rollers has a respective rotational axis perpendicular to the outer edges of the metal strip as the metal strip enters the bending roller station, and an axial midplane perpendicular to the rotational axis. The axial midplanes of the rollers lie generally within the respective roller set plane. Within each of the bending roller sets, the inside roller contacts a first side of the metal strip along the bending line, and the outside upstream roller contacts the second side of the metal strip along the bending line. The outside downstream roller contacts the second side of the metal strip downstream of the bending line and is positioned so as to cause the strip to bend at

the bending line for forming the metal strip into a spiral cylinder, with the outer edges of the strip adjacent each other.

Brief Description Of The Drawings FIG. 1 is a top plan view of a machine embodying the invention; FIG. 2 is a side elevational view taken on line 2-2 of FIG. 1; FIG. 3 is an end elevational view taken generally on line 3-3 of FIG. 1, additionally showing spiral pipe being produced, with a portion cut away; FIG. 4 is a three-dimensional view from the front of the machine, generally corresponding to FIG. 3, but also showing an optional stabilizing hoop; FIG. 5 is a three-dimensional view from the rear of the machine; FIG. 6 is a schematic representation of the arrangement of rollers within the bending roller station; FIG. 7 is a cross-sectional view taken on line 7-7 of FIG. 6; FIG. 8 is a cross-sectional view taken on line 8-8 of FIG. 6; FIG. 9 is an enlarged three-dimensional view of the bending roller station as viewed from the output end of the machine, generally from the top right front corner, in the same orientation as FIG. 4; FIG. 10 is an enlarged three-dimensional view of the bending roller station, also as viewed from the output end of the machine, generally from the top left front corner; FIG. 11 is an enlarged end elevational view of the bending roller station, viewed from the output end, in the same orientation as FIG. 3; FIG. 12 is an enlarged three-dimensional view of the bending roller station, viewed from the input end,

generally from the top left rear corner, opposite the view of FIG. 9; FIG. 13 is an enlarged three-dimensional view of the bending roller station, also viewed from the input end, taken generally from the right corner, opposite the view of FIG. 10; FIG. 14 is an enlarged end elevational view of the bending roller station, viewed from the input end, opposite the view of FIG. 11; and FIG. 15 is a right side elevational view of the bending roller station, taken on line 15-15 of FIG. 11 or on line 15-15 of FIG. 14.

Best Mode for Carrying Out the Invention FIGS. 1-5 show in overview a machine 30 embodying the invention for producing spiral seamed hollow pipe, of the type which is commonly employed in air conditioning and heating installations. FIGS. 3-5 additionally depict a portion of the spiral pipe 32 being produced, and FIGS. 4 and 5 additionally depict a metal strip 34 being input to the machine 30 from a supply coil (not shown). The metal strip 34 is made of sheet metal, and is typically 5.34 inches (137 mm wide). The metal strip 34 has a first side 36 (top side in FIGS. 4 and 5) which becomes the inside surface of the spiral pipe 32; and a second side 38 (the bottom hidden side in the orientation of FIGS. 4 and 5) which becomes the outside surface of the spiral pipe 32. The strip also has outer edges 42 and 44, which are brought adjacent to each other and joined by a lockseam 46 as the spiral pipe 32 is produced.

Structurally, the machine 30 includes a table- like stationary machine base 48, having a front edge 49.

The machine base 48 also serves as an equipment cabinet, housing an hydraulic pump (not shown), an air compressor (not shown) and a DC power supply (not shown) for powering a plasma cutting torch 50 (FIGS. 1-3), and an exhaust

blower (not shown) for drawing exhaust gas from operation of the plasma cutting torch 50 through an exhaust gas collector 52.

For adjustment purposes, pivotally attached to the stationary machine base 48 is a pivotable base 54.

The pivotable base 54 pivots on a vertical pivot axis 56 which is perpendicular to and intersects the central axis of the spiral pipe 32. A set of ball bearing rollers 58 supports the pivotable base 54 on the machine base 48, allowing the pivotable base 44 to pivot freely on its pivot axis 46.

Attached to the pivotable base 54 is a pointer 60 which cooperates with. a semi-circular indicia element 62 when adjusting the angle of the pivotable base 54. The semi-circular indicia element 32 is attached to the stationary machine base 48, and has a center of curvature on the pivot axis 56. Indicia 64 are non-linearly spaced and located as determined by the geometry involved, and correspond to a spiral pipe 32 diameter adjustment range from four-inch diameter near the more extreme angle adjustment end 66 of the indicia element to one hundred- inch diameter near the relatively shallow angle adjustment end 68.

Mounted to the pivotable base 54 and carried thereby are a flange forming roller station 70, a passive feed section 72 and a bending roller station 74.

Associated with the flange forming roller station 70 and also mounted to the pivotable base 54 is a right angle gear drive unit 76 connected to the flange forming roller station 70 via a rotary coupling 78, as well as an hydraulic drive motor 80 mounted to the gear drive unit 76. Within the flange forming roller section 70 there are a set of flange forming rollers 82 which form the outer edges 42 and 44 of the strip 34 into mating profiles suitable for forming the lockseam 46. In addition, the flange forming rollers 82 serve to drive the metal strip 34 through the bending roller station 74.

The bending roller station 74, as well as the flange forming roller station 70 and the passive feed section 72 thus pivot with the pivotable base 54. The central axis of the pipe 32 being produced, however, is always parallel to the front edge 49 of the machine base 48.

Also mounted to the machine base 48 is a pipe cutting apparatus, generally designated 86. In the illustrated embodiment, the pipe cutting apparatus 86 includes the plasma cutting torch 50. However, other cutting devices may be employed, such as rotatable knife blades (not shown). Conversely, it will be appreciated that a plasma cutting torch may be employed in combination with other machines for producing spiral duct, operating for example on the principles of the Castricum or Hale et al U. S. patents referenced above.

The pipe cutting apparatus 86 more particularly includes a cutter support boom 88 mounted in cantilever fashion to a pedestal 90. The pedestal 90 is adjustable in height, and includes an upper section 92 attached to the cutter support boom 88, a lower section 94 mounted to the machine base 48, and a shaft 96 of an hydraulic cylinder (not generally shown) to which the upper pedestal section 92 is fixed and which slides vertically through an aperture in the lower section 94 of the pedestal 90. In the illustrated embodiment, the cutter support boom 88, in conjunction with the pedestal 90 and the hydraulic cylinder shaft 96, serves the dual purposes of supporting the plasma cutting torch 50, and serving as a releasable clamping element for applying pressure between upper and lower elements of the bending roller station 74, as is described hereinbelow in greater detail.

The cutter support boom 88 has a free end portion 98 which carries the plasma cutting torch 50.

When cutting is to take place, the free end portion 98 moves at the same rate and in the same direction as spiral pipe 32 being produced advances so that the free end

portion 98 and therefore the plasma cutting torch 50 remain in the same axial position with reference to a predetermined point on the spiral pipe being produced 32.

A rectangular cut at a right angle to the axis of the pipe 32 being produced is achieved, notwithstanding axial motion of the spiral pipe 32.

Referring now, in addition to FIGS. 1-5, to the conceptual views of FIGS. 6-8, as well as the various enlarged three-dimensional views of the bending roller station 74 of FIGS. 9-15, within the bending roller station 74 the metal strip 34 is continuously bent on a bending line 100 which is parallel to the central axis of the spiral pipe 32 being produced. The bending line 100 also intersects the pivot axis 56 of the pivotable base 54 at a right angle. As is perhaps best seen in FIG. 6, the bending line 100 extends generally across the metal strip 34, but at an angle offset from a right angle with reference to the edges 42 and 44 of the metal strip 34 as the metal strip enters the bending roller station 74. The particular offset angle is determined by calculation based on the width of the strip 34 and the diameter of the spiral pipe 32 being produced, and is consistent with the pivot angle of the pivotable base 54 as set employing the pointer 60 and indicia element 62.

Within the bending roller station 74 there are a plurality of bending roller sets. In the disclosed embodiment, there are five bending roller sets, designated 102,104,106,108 and 110. The bending roller set 102 may also be referred to as the interior end roller set because it is just within the interior of the spiral pipe 32 being produced, as is perhaps best seen in FIG. 3.

The bending roller sets 102,104,106,108 and 110 include respective inside rollers 112,114,116,118 and 120; respective outside upstream rollers 122,124, 126,128 and 130; and respective outside downstream rollers 132,134,136,138 and 140. Each of the rollers 112,114,116,118', 120,122,124,126,128,130,132,

134,136,138 and 140 has a respective rotational axis which is perpendicular to the outer edges 42 and 44 of the metal strip 34 as the metal strip 34 enters the bending roller station 74. Each of the rollers also has an axial midplane perpendicular to its rotational axis.

Referring in particular to the cross section of FIG. 8, which depicts the bending roller set 104, the inside roller 114 contacts the first side 36 of the metal strip 34 along the bending line 100, and the outside upstream roller 124 contacts the second side 38 of the metal strip 34 also along the bending line 100. The inside roller 114 and the outside upstream roller 124 thus cooperate to define a pinch roller pair. The outside downstream roller 134 in FIG. 8 also contacts the second side 38 of the metal strip 34, and is positioned so as to cause the strip 34 to bend at the bending line 100 for forming the metal strip into a spiral cylinder, that is, into the form of the spiral seamed pipe 32 being produced, with the outer edges 42 and 44 of the strip 34 adjacent each other.

The bending roller sets 102,104,106,108 and 110 are positioned generally side by side generally in respective roller set planes which are parallel to each other and to the outer edges of 42 and 44 of the metal strip 34. The roller set planes are also perpendicular to the metal strip 34 as the metal strip 34 enters the bending roller station 64. The actual midplanes of the rollers lie generally within the respective roller set planes, although some variation is possible.

In FIG. 6, the outside upstream rollers 122, 124,126,128 and 130 are hidden by the inside rollers 112,114,116,118 and 120. However, the outside upstream rollers 122,124,126,128 and 130 are visible in the cross section of FIG. 7.

Since FIG. 7 is taken on line 7-7 of FIG. 6 which coincides with the bending line 100 that extends across the metal strip 34 at an angle offset from a right

angle, and since the axes of the inside rollers 112,114, 116,118 and 120 and of the outside upstream rollers 122, 124,126,128 and 130 are perpendicular to the outer edges 42 and 44 of the metal strip 34, in FIG. 7 portions of the end surfaces 142,144,146,148 and 150 of the respective inside rollers 112,114,116,118 and 120 are visible; as are portions of respective end surfaces 152,154,156,158 and 160 of the outside upstream rollers 122,124,126,128 and 130.

With reference to the orientation of FIG. 8, to ensure that the metal strip 34 enters straight into the pinch roller pairs 112,122; 114,124; 116,126; 118,128; and 120,130; the bending roller station 74 additionally includes upstream pinch roller pairs 164,166,168 and 170. The upstream pinch roller pairs 164,166,168 and 170 are all visible in the input end elevational view of FIG. 14, and include respective first side (top) pinch rollers 174,176,178 and 180, as well as respective second side (bottom) pinch rollers 184,186,188 and 190.

FIG. 8 shows the relative orientation of the first side upstream pinch roller 174 and the second side upstream pinch roller 184 comprising the upstream pinch roller pair 164. In FIG. 6, the second side upstream pinch rollers 184,186,188 and 190 are hidden by the first side upstream pinch rollers 174,176,178 and 180.

Within the flange forming roller section 60 (FIGS. 1-5), the flange forming rollers 82, in a conventional manner, form the outer edges 42 and 44 of the metal strip 34 into mating profiles suitable for forming the lockseam 46. The passive feed section 72 includes rollers and guides for stabilizing the metal strip 34 prior to entering the downstream bending roller station 74, in particular, to provide lateral stability.

In addition to the flange forming rollers 82 which form the basic profiles, in order to further form the metal strip 34 edge profiles into a suitable configuration for forming a lockseam, there is a

stationary finger 192 which engages the strip 34 edge 42 to aid in forming the lockseam 46, and a roller 194 which engages the strip 34 edge 44 to form the"V configuration 196 visible in FIG. 7.

Still referring to FIG. 7, within the interior end bending roller set 102, the inside roller 112 and the outside upstream roller 122 also define a seam roller pair 112,122 to compress adjacent outer edges of the strip to form the lockseam 46. Accordingly, there is circumferential groove 198 in the outside upstream roller comprising half of the seam roller pair 112,122, of appropriate depth.

During operation, the metal strip 34 enters the machine 30 more or less continuously in the direction indicated by the arrow 36. Within the bending roller station 74 the outer edges 42 and 44 of the strip 34 are formed into mating profiles suitable for forming the lockseam 46. Within the bending roller station 74, the strip 34 is bent to form the curvature of the pipe 32 being produced, and additionally the lockseam 46 is completed. During the process of producing pipe 32, the pipe 32 rotates in the direction indicated by the arrows 200, and moves axially away from the bending roller station 74 in the direction indicated by the arrows 202, parallel to the front edge 49 of the machine base 48, regardless of the angle setting of the pivotable base 54.

The pipe 32 is supported on a floor-mounted roller stand 204 as it is produced and emerges from the bending roller station 74.

To ensure that the pipe 32 emerges in a straight and undistorted manner from the machine 30, and to ensure correct final sizing notwithstanding any slight misadjustment of the bending roller sets 102,104,106, 108 and 110, a stabilizing hoop 206 (FIG. 3) may be provided. The stabilizing hoop 206 is attached via a mount 208 to the machine base 48. The stabilizing hoop is helical in configuration to match the pipe 32 being

produced, and has a width so as to fit between adjacent turns of the lockseam 46. The circumferential length is approximately one turn.

The spiral pipe 32 travels inside the stabilizing hoop 206 as the pipe 32 emerges from the bending roller station 74. However, the curvature of the spiral pipe 32 is formed by the rollers within the bending roller station 74, and not by frictional engagement with the inside of the stabilizing hoop 206, other than what is required for alignment and final sizing. The inside of the stabilizing hoop may be provided with a low-friction surface (e. g. Teflon), or some lubrication may be used as required depending on the speed of the machine 30.

With particular reference to the enlarged three-dimensional views of FIGS. 9-15, the manner in which the rollers of the bending roller sets 102,104,106,108 and 110 are mounted will now be described.

Within the bending roller station 74 there is a lower roller base 230, mounted securely to the pivotable base 54. As may be seen in FIGS. 9-11, the outside downstream rollers 132,134,136,138 and 140, which effect the bending, have respective individual outside downstream roller support blocks 232,234,236,238 and 240, mounted to the lower roller base 230. The heights of the outside downstream roller support blocks 232,234, 236,238 and 240, and thus the heights of the outside downstream rollers 132,134,136,138 and 140 themselves, are determined by respective individual vertical shim plates 242,244,246,248 and 250. The shim plates 242, 244,246,248 and 250 can be changed out for making spiral pipe of different diameters.

With reference to the three-dimensional views of FIGS. 12 and 13, as well as the elevational view of FIG.

14, the outside upstream rollers 124,126,128 and 130 are similarly carried by respective outside upstream roller support blocks 264,266,268 and 270. These likewise have respective vertical shims (not shown). The outside

upstream roller support blocks 264, 266, 268 and 270 also carry the second side upstream pinch rollers 184,186,188 and 190. For positive positioning to ensure that the outside upstream rollers 124,126,128 and 130 are located along the bending line 100, the outside upstream roller support blocks 264, 266, 268 and 270 bear against a lower cam plate 282 of stair step configuration. The lower cam plate 282 is changed out when it is desired to manufacture spiral pipe of a different diameter, thereby changing the angle of the bending line 100 as required.

As an alternative to providing a set of different lower cam plates 282 to adjust for making spiral pipe in different diameters, a linkage (not shown) may be employed. On one form of linkage, a fixed plate (not shown) which does not move with the pivotable base 54 is located below the lower roller base 230. The fixed plate has a slot (not shown) which is parallel to the bending line 100 and in the same plane as the bending line 100 and the axis of the pipe being produced. Pins (not shown) aaare attached to the individual ones of the roller support blocks 264, 266, 268 and 270 directly below the respective outside upstream rollers 124,126,128 and 130, and engages the slot. During adjustment, as the pivotable base 54 rotates, the roller support blocks 264, 266, 268 and 270 slide on the roller base 230, maintaining the outside upstream rollers 124,126,128 and 130 on the bending line 100. In addition, the support blocks 234, 236, 238 and 240 for the bending rollers 134,136,138 and 140 are linked to the respective support blocks 264, 266, 268 and 270 to move horizontally therewith during adjustment, while at the same time allowing separate vertical adjustment of the bending roller support blocks 234,236,238 and 240.

No such adjustment for the outside upstream roller 122 is required, since the roller 122 is on the pivot axis 56, and contacts the second side 40 of the

strip 34 at the intersection of the pivot axis 56 and the bending line 100.

The inside rollers 112,114,116,118 and 120 are carried by a removable upper roller support plate 290.

The upper roller support plate 290 has a downwardly- facing locating groove 292 which engages a support structure (not shown in FIGS. 9-15) for positively locating the upper roller support plate 290 with reference to other elements of the bending roller station 74. The upper roller support plate 290 is held in position by downward pressure from the cutter support boom 88. Thus, the cutter support boom 88 is raised by operation of the hydraulic cylinder shaft 96 so that the upper roller support plate 290 can be removed for adjustment purposes (and along with it the inside rollers 112,114,116,118 and 120). The upper roller support plate 290 is subsequently clamped into position by lowering the cutter support boom 88.

The inside roller 112, which is on the pivot axis 56, is carried directly by the upper roller support plate 290. The remaining inside rollers 114,116,118 and 120 have respective inside roller support blocks 304,306, 308 and 310 adjustably secured to the upper roller support plate 290, mounting elements of which are positioned within respective adjustment slots 314,316,318 and 320.

For positive positioning to ensure that the inside rollers 114,116,118 and 120 are located along the bending line 100, the inside roller support blocks 304, 306,308 and 310 bear against an upper cam plate 322, an edge of which is visible in FIGS. 12-14. The upper cam plate 322 is of stair step configuration like the lower cam plate, and likewise is changed out when it is desired to manufacture spiral pipe of a different diameter, thereby changing the angle of the bending line 100 as required. Alternatively, the linkage described above may also be connected to the support blocks 304,306,308 and 310.

No such adjustment for the inside roller 112 is required, since the roller 112 is on the pivot axis 56, and contacts the first side 38 of the strip 34 at the intersection of the pivot axis 56 and the bending line 100.

In the illustrated embodiment, adjustment to produce spiral pipe of different diameters is achieved by changing out the stair step cam plates 282 and 322 and correspondingly moving the inside rollers 114,116,118 and 120 and the outside upstream rollers 124,126,128 and 130 so that these rollers contact the metal strip 34 on a bending line 100 appropriate for the pipe 32 diameter; by adjusting the angular position of the pivotable base 54 on the pivot axis 56, aided by the pointer 60 and the semi- circular indicia element 62, to an angle corresponding to the angle of the bending line 100 ; and by adjustment of the height of the outside downstream rollers 132,134, 136,138 and 140 (which effect the actual bending) by changing out the vertical shim plates 242,244,246,248 and 250.

As an alternative to the vertical shim plates 242,244,246,248 and 250 to adjust for making spiral pipe in different diameters, an adjustable platform, (not shown) may be provided, with an adjustment screw, to move the entire gang of outside downstream rollers (bending rollers) 132, 134,136,138 and 140 together. In this case, the bending roller 132 (which, in the illustrated embodiment, has a larger diameter and is offset from the others), is the same diameter as and is in line with the other bending rollers 134,136,138 and 140.

These various positions may also be set by hydraulically actuated servomechanisms employing a suitable computer-based controller, simplifying the process of adjustment.

In addition, the positions of the outside downstream rollers 132,134,136,138 and 140 may be adjusted on-the-fly to change the angle of bending as the

metal strip 34 exits the bending roller station 74, alternating between no bending at all and a curve of predetermined radius, thereby producing flat oval seamed metal duct work directly, without requiring the use of a separate ovalizer machine.

As another variation, a duct transition section of tapered diameter can be produced by varying the positions of the rollers within the bending roller station 74 as is appropriate, as well as the angular position of the pivotable base 54, likewise with servomechanism control employing a suitable controller.

While the novel features of the invention have been illustrated and described herein, it is realized that numerous modifications and changes will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit and scope of the invention.

Industrial Applicability The way in which the invention is capable of being exploited and the way in which it can be made and used will be apparent from the foregoing.