US3750439A

US3750439A - Method and apparatus for making corrugated pipe

Info

Publication number: US3750439A
Application number: US00107920A
Authority: US
Inventors: H Pratt
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-01-20
Filing date: 1971-01-20
Publication date: 1973-08-07
Anticipated expiration: 1990-08-07

Abstract

Corrugated pipe is made from flat strips of corrugated material by helically coiling the strip about the pipe axis. A plurality of laterally spaced ball raceways graze the strip from both sides and helically deform it by rollingly engaging the strip corrugations with the balls as the strip is fed past the raceways. Coiled strip edges are simultaneously seamed. A flying shear intermittently severs the flat strip along a diagonal line for the production of limited length pipe sections having straight ends.

Description

United States Patent [1 1 Pratt 11 11 3,750,439 [451 Aug. 7, 1973 METHOD AND APPARATUS FOR MAKING CORRUGATED PIPE [75] Inventor: Howard G. Pratt, Brownsville, Calif.

[73] Assignee: Eugene W. Sirachenko, Redding,

Calif.

[22] Filed: Jan. 20, 1971 [21] Appl. No.: 107,920

[52] U.S. Cl 72/43, 72/49, 72/132, 72/135 [51] Int. Cl. B211) 45/02, B21c 37/12 [58] Field 01 Search 72/49, 43, 50, 135, 72/137, 132

[56] References Cited UNITED STATES PATENTS 6/1914 Pratt ..72/49 3/1943 Odor ..72/50 3,411,333 11/1968 Frankel 72/43 3,073,944 1/1963 Yuter 8/1966 Lombardi Primary Examiner-Charles W. Lanham Assistant Examiner-Robert M. Rogers Attorney-Townsend and Townsend [57] ABSTRACT Corrugated pipe is made from flat strips of corrugated material by helically coiling the strip about the pipe axis. A plurality of laterally spaced ball raceways graze the strip from both sides and helically deform it by rollingly engaging the strip corrugations with the balls as the strip is fed past the raceways. Coiled strip edges are simultaneously seamed. A flying shear intermittently severs the flat strip along a diagonal line for the production of limited length pipe sections having straight ends.

24 Claims, 7 Drawing Figures PATENTED AUG 7 I875 sum 1 or 3 N QI I N V E NTOR. HOWARD G. PRATT T WMJHTWJ ATTORNEYS PAIENI LU AUG 7 I975 SHEU 3 0f 3 FIG 5 60/ 28 he \\A INVENTOR.

HOWARD e. PRATT BY WM! ATTORNEYS METHOD AND APPARATUS FOR MAKING CORRUGATED PIPE BACKGROUND OF THE INVENTION The present invention relates to the continuous manufacture of corrugated pipe by helically winding corrugated strip. Such pipe manufacturing, per se, is known.

Prior art corrugated pipe manufacture employed rigid, helically curved forming rods that engaged the flat strip and helically coiled it. The rods extended over a substantial portion of the pipe circumference and resulted in large friction forces between the strip and the rods. The power consumption of such machines is objectionably high. In addition, the sliding engagement between the forming rods and the strip results in objectionable markings and scratching of the pipe exterior and requires relatively elaborate lubricating means. U.S. Pat. No. 2,136,942 is illustrative of such pipe forming method and apparatus.

Attempts have been made to eliminate or at least reduce the shortcomings encountered with forming machines constructed in accordance with the above referenced patent. The rigid, helically shaped forming rods were replaced with forming rolls that engaged the strip and helically deformed it as it passed them. A forming roll was provided for each strip corrugation and they were arranged on a line parallel to the finished pipe axis with their axes perpendicular to the length of the flat strip. US. Pat. No. 3,247,692 is exemplary of such attempts.

Although the latter type of corrugated pipe forming machines exhibited advantages over the earlier described machines, they have problems of their own. The forming rolls are subjected to large forces in both radial and axial directions. The rolls that determine the actual deformation of the strip are in point contact with the strip. The deformation forces are transmitted to the relatively stiff corrugated strip at these points. The large forces subject the rolls to substantial wear and tear. Additionally, space limitations prevent a mounting of the rollers which adequately supports them and which limits the sheet thickness that can be coiled into pipe with such machines.

These corrugated pipe making machines were moreover constructed to permit adjustability in the relative positions of the rolls so that pipes of different diameters could be formed. Although this is theoretically desirable in practice such an approach requires extensive and critical alignments of the rolls that can only be performed by sparce, highly skilled and expensive labor. Moreover, the adjustment can be lost during operation of the machine and there is always the danger that an adjustment error or mistake remains undetected for extended periods of times so that the finished pipe is of a diameter other than the desired diameter. Since pipe consumers, such as highway departments, irrigation districts and the like have relatively rigid pipe size tolerances, whole production runs can be wasted. Thus, significant economic losses can result because a relatively harmless error went undetected.

Prior art corrugated pipe forming machinery also provided flying saws for cutting the endlessly manufactured pipe to length. Such saws moved with the pipe as it is manufactured and sever the pipe at the desired location. Due to the depth of pipe, its rolling motion during the manufacture and its forward motion as it is produced, the flying saws are relatively intricate, expensive to construct and susceptible to malfunctioning.

Furthermore, a saw leaves heavy, rugged burrs which require expensive hand labor for their removal. This slows down the manufacturing operation and represents a sizeable portion of the overall labor costs of corrugated pipe.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for forming corrugated pipe from helically coiled corrugated strip which reduces or eliminates shortcomings found in prior art machinery. Briefly, in accor dance with the present invention, flat corrugated strip is helically deformed by feeding it past helically shaped ball raceways. The raceways extend over a substantial arc, provide for rolling engagement between the balls and the strip being deformed and thus provide for strip support over the length it takes to fully deform it at a multiplicity of longitudinally spaced support points defined by the balls. Moreover, the balls and, strip are in rolling engagement to limit frictional forces developed between them. The power requirement of such a machine is, therefore, relatively low while the deforming members, namely the ball raceways, are subjected to relatively low, evenly distributed forces to prevent a premature wear or destruction of the raceways due to large concentrated forces as encountered in some prior art pipe forming equipment.

The apparatus of the present invention is rigid and provides a raceway deforming set for each desired pipe size. Once the sets are fine adjusted, preferably at the factory, they are interlocked. There is generally no need for their further adjustment so that they can be simply mounted in place and withdrawn from the machine for the production of different size pipe. Heretofore encountered tedious, time consuming and troublesome adjustments of the strip deforming members before a new pipe size can he produced are eliminated. Moreover, the danger of undetected errors in the-adjustment of the forming mechanism whenever a new pipe size is produced, and the potentially large resulting economic loss, are eliminated.

The rigid mounting of the raceways in high-strength cross bars at the rolling station and the multiple engagement of the sheet being deformed not only reduces wear and tear but enables substantial increases in the overall rolling force applied to the sheet. Substantially heavier gauge materials can thus be rolled with the machine of the present invention.

The present invention further provides a flying shear or the like mounted to the frame of the machine for severing the flat strip along a diagonal before the strip is deformed by the raceways. The angularity of the diagonal is so chosen that it forms flat ends or beginnings, repsectively, of pipe sections of the desired length. The heretofore necessary relatively complicated, costly and fail prone flying saw for severing pipe sections from continuously produced pipe is thereby eliminated. The sheared edges are clean and smooth and do not require the earlier referred to costly and time consuming hand deburring. This results in a substantial reduction in the labor cost of corrugated pipe.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an apparatus for helically coiling flat, corrugated strip into corrugated pipe constructed in accordance with the invention;

FIG. 2 is a front elevational view taken on line 2-2 of FIG. 1 of the mechanism for helically deforming the strip in accordance with the invention;

FIG. 3 is an enlarged, cross sectional side elevational view taken approximately on line 3-3 of FIG. 1 and illustrates the strip deforming ball raceways, the raceway mounting cross bars are vertically spread apart to enable an unobstructed view of both the upper and the lower raceways;

FIG. 4 is a fragmentary plan view, with parts broken away, of the strip deforming mechanism and is taken on line 4-4 of FIG. 3;

FIG. 5 is a schematic section through the strip deforming mechanism and is taken along the center line of the ball raceways;

FIG. 6 is a fragmentary, sectional view illustrating the interengagement between the ball raceways and the strip as it is being formed, and the formation of the seam between adjacent edges of the coiled strip, and is taken on line 6-6 of FIG. 1; and

FIG. 7 is a fragmentary elevational view similar to FIG. 6, and illustrates the ball raceway arrangement and an edge seamer employing a ball raceway.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a corrugated pipe making apparatus 10 constructed in accordance with the invention broadly comprises a frame 12 on which a flat strip of sheet material 14 driven by drive rolls 15, is guided from a supply roll or the like (not separately shown) past a flying shear 16, conventionally arranged corrugating roller sets 18 to form a strip 20 of corrugated material and to a pipe rolling station 22. At the rolling station, the corrugated strip is helically coiled between a pair of jaws 24 having upper and lower ball raeeways 26 and 28, respectively, which engage the corrugated strip from both sides and deform it. The edges of the coiled strip are secured to each other between seaming rolls 30 to form an endless helical seam 32 that firmly interengages the helical corrugaged coils to thus form corrugated pipe 34. During the manufacture ofthe pipe corrugated strip is continuously coiled and the finished pipe moves away from rolling station 22 in an upwardly slanted direction, as viewed in FIG. 1, while being supported by suitably positioned support rollers 36 that permit rotational movement of the pipe about its axis and an axial movement as the pipe is being manufactured.

To eliminate the need for severing the manufactured pipe into pipe sections of the desired length, as would be necessary ifa continuous length of strip were coiled and which is relatively impractical as pointed out about, flying shear 16 is movably mounted on tracks 38 engaged by rollers 40. Preferably adjustable, conventional means is provided for intermittently moving the shear in synchronism with strip 14 towards rolling station 22 while the shear severs the strip and for thereafter returning it to its original position.

Rollers 40 and tracks 38 are constructed so that skewing or lateral motions of the shear are prevented. Alternative mounts for the shear permitting its longitudinal movements while preventing sideway motions can of course be employed. The shear includes means for severing the flat strip 14 along a diagonal line 42 the angularity of which is so chosen that pipe sections with straight ends are obtained upon completely coiling a diagonally severed corrugated strip. The angularity of the diagonal shear cut is adjustable by suitably mounting the shear to enable the construction of straight pipe ends on pipes of differing diameters.

Referring now to FIGS. 1 through 4, the construction of the corrugated strip deforming jaw pair 24 and

raceways

26, 28 at rolling station 22 is described in greater detail. The jaws are defined by upper and lower cross bars 44and 46, which extend a substantial distance beyond the edges of the corrugated strip 20 and are vertically aligned (as seen in FIG. I) with the axis of pipe 34. At one end the cross bars are bolted together with threaded bolts 48. A set of wedges 50 are placed between the bar, keeps the other end of the cross bars spaced apart and permits adjustment of the spacing between the bars by correspondingly adjusting the relative position of the wedges. The underside of lower cross bar 46 is pivotally engaged by an upright pin 52 and threaded bolts 54 secure the cross bars to mounting plate 49 of frame 12. The centers of bolts 54 and pivot pin 52 are aligned with each other and with the axis of pipe 34. Mounting plate 49 includes additional apertures 56 (shown in FIG. 1) which are so positioned with respect to the center of pivot pin 52 that the apertures are aligned with the pin center along the axes of other pipe sizes. Jaw pairs (not shown) for other pipe sizes, having upper and lower raeeways constructed as more fully set forth hereinafter, can be dropped over pin 52 and secured with threaded bolts (not shown) extending through the respective apertures 56 to thereby automatically align and correctly position such jaws for the manufacture of different pipe sizes. Tedious, time consuming and error prone adjustments of the corrugated strip deforming means are thereby eliminated.

Turning now to the construction of the strip deforming raceways, a plurality of laterally spaced upper raceways 26 have aft ends 58 (facing towards flying shear l6) aligned with valleys 60 of corrugated strip 20, a spacing between them equal to the spacing of the corrugations and an open portion 62 that permits balls 64 to protrude into engagement with the corrugated strip. The open raceway portion includes a first, downwardly sloped or curved section 66 which, together with an upwardly curved section 68 of lower raceway 28 forms a mouth 70, and a deforming section 72 that is compoundly curved sideways and downwardly. Balls in the deforming section engage the side of corrugated strip 20 that ultimately forms the exterior surface of pipe 34, guide the strip parallel to the undeformed strip corrugations along a straight line to an initialdeformation point 74, and from there on guide and deform the strip along the compoundly curved path to a point 76 at which the deformation terminates. The finished formed strip is helically coiled with a diameter equal to the desired pipe diameter. From terminal point 76 the balls preferably continue some distance in engagement with the strip corrugations and are then recirculated via a tubular loop 78, through bores 80 extending across the width of upper cross bar 44 and hence back down towards downwardly curved section 68 and the initial deformation point 74.

Lower raceways 28 are offset with respect to the upper raceways 26 by one-half the spacing of the strip corrugations (see FIGS. 1, 2, 4 and 6) so that balls 64 in the lower raceway engage ridges 82 of the corrugated strip from the side of the strip that ultimately forms the interior surface of pipe 34. The lower raceways have an open raceway portion 84 which begins with the open, upwardly curved raceway length 68 that defines the lower half of mouth 70, continues on a straight line to initial deformation point 74 and then along a convex, compoundly curved downwardly and sideways extending path parallel to the path defined by deforming section 72 of upper raceway 26. During the deformation the open raceway portion 84 of lower raceway 28 assures intimate contact between the corrugated strip and the upper deforming section 72 to precisely deform the strip into the desired helical coil shape. The lower raceway includes

tubes

85 and 86 which connect to transverse apertures 88 in lower cross bar 46 for the recirculation of balls towards mouth 70 and initial deformation points 74.

To enable fine adjustments of the strip deforming upper raceway 26, means is provided for changing the degree of curvature of deforming section 72 to a limited extent at least in one plane. In the presently preferred embodiment of the invention, such means comprises a turn buckle 90 connected to upper cross bar 44 andto the far end of tubular raceway loop 78. By turning the turn buckle in one or the other direction, the curvature of the deforming section can be increased or decreased until the precise curvature for obtaining the desired pipe diameter is set. The lower raceway, whose main function is to assure intimate contact between the corrugated strip and the upper raceway, does not require such fine adjustment. To assure the intimate contact between the raceway and the corrugated strip, the vertical spacing between cross bars 44, 46 and thus between upper and

lower raceways

26 and 28 is adjusted with wedge set 50 in the above described manner.

In use, corrugated strip is advanced into mouth 70, past initial deformation point 74 and the deformation terminal point 76 to helically coil the strip by providing a power drive (not separately shown) for corrugating rollers 18. The strip is thereby simultaneously advanced and corrugated. The cross bars are so positioned and constructed that the upper and lower raceways are aligned with the valleys and ridges, respectively, of the corrugated flat strip. As the leading edge of the corrugated strip approaches mouth 70, the protruding portions of balls 64 automatically bias the leading edge into alignment with the vertical gap between the upper and lower raceways. Thereafter, the forward motion imparted to the corrugated strip by rollers 18 pushes the strip along the raceways and thereby deforms it. The many balls of each raceway in contact with the strip provide a substantially uniform lateral support for the strip as it moves past rolling station 22. Moreover, they provide a gradual and continuous deformation of the strip. There are, therefore, no large peak radial or axial forces acting on one deforming member, i.e., ball, which causes its rapid wear and tear. Furthermore, thefriction developed between the moving corrugated strip and the balls causing its deformation is rolling friction and, therefore, relatively low so that the required power for deforming the strip is low and marking and scratching of the strip surface is avoided.

Referring now briefly to FIGS. 3 and 4, to assure adequate lubrication of balls 64 in

raceways

26 and 28 and to blow out slag and other foreign materials that might accumulate in the raceway,

manifold tubes

92, 93, 94 and 95 are provided and run parallel to cross

bars

46, 48 across the raceways. The tubes are suitably connected to the raceways, as with clamps, screw connections or by soldering or brazing them to the raceways (not shown), and are in fluid communication with the interior of the raceways via bores 96. Lubricated air, comprising compressed air'and a fine mist of oil, graphite particles or similar lubrication materials is supplied to the manifolds and blown into the raceways through connecting bores 96. Balls 64 can thereby be continuously or intermittently lubricated to reduce friction between the balls and the raceways as well as the corrugated strip 20 being deformed. At the same time foreign particles are moved along the raceways and discharged through the open raceway portions. This latter aspect eliminates the possibility of stuck balls due to a clogging of the raceways with foreign materials such as slag loosened from the corrugated strip during the deformation thereof. To facilitate the discharge of foreign materials from lower raceway 28 it can be provided with one or more downwardly facing slag discharge openings (not separately shown) in the

tubular guide members

85 and 86 of the raceway. Slag blown to the discharge opening call then drop gravitationally from the raceway.

Referring now to FIGS. 1, 6 and 7, pipe rolling apparatus 10 includes forming rolls 98 along the edges of strip 14 to form end folds 100 which are subsequently engaged as partially shown in phantom lines in FIG. 6. The precise shape of the end folds can be selected to suit the particular need. Various end fold configurations are known and can be selected. Representative of good folds are the following issued patents: U.S. Pat. No. l,394,ll6; U.S. Pat. No. l,9l8,l37; and British Pat. No. 4,513. It is presently preferred to employ edge fold configurations which yield a final seam 32 that is flush on the pipe exterior as illustrated in FIG. 6. Undesirable outward protrusions of the seam which can cause problems when joining adjacent corrugated pipe sections in the field are thereby eliminated.

During the rolling of pipe, the end folds 100 of just coiled corrugated strip are continuously brought in overlapping relationship with corrugated strip being helically coiled as illustrated in phantom lines on the left-hand side of FIG. 6. One or more seam roller sets 30 are provided to close the end folds in one or more steps until the pipe is finished seamed. FIG. 6 illustrates in detail the finished seam between

coacting rollers

102 and 104 of set 30.

To eliminate undesirable vibrations of already finished rolled and seamed pipe during the seaming operation,

additional raceways

106 and 108 are provided which are positioned on the side of seaming rollers 30 opposite from the corrugated

strip deforming raceways

26 and 28. The additional raceways have a spiral curvature, as seen in FIG. I, and firmly support and guide the rotating pipe downstream (in an upwardly slanted direction as seen in FIG. 1 and to the right as seen in FIG. 6) along the precise desired path in a vibrationally less manner. This addedsupport facilitates the ease and accuracy with which the pipe is seamed. The additional raceways I06 and 108 are secured to transverse cross bars 44 and 46 in the same manner in which

strip deforming raceways

26 and 28 are secured to the bars.

Referring briefly to FIG. 7, in another embodiment of the invention, the pipe seaming operation is performed by coacting upper and lower

seaming ball raceways

110, 112, respectively. The seaming raceways are carried by upper and lower cross bars 44 and 46, engage the strip end folds along a helical path and gradually compress the folds until the pipe is finished seamed. It will be understood that it is preferred to construct the seaming raceways in the same manner as the construction of the

strip deforming raceways

26 and 28, that is by providing tubular ball guides and recirculating the balls through bores across the width of cross bars 44 and 46 although FIG. 7 does not show that construction in detail and merely schematically illustrates the provision of the raceways in the cross bars. Furthermore, additional finished pipe guiding ball raceways as illustrated in FIG. 6 are preferably used in conjunction with the seaming

raceways

108, 110 to isolate the seaming operation from adverse vibrations and movement of already finished pipe.

As an alternative to the formation of mechanical lock seams as described above the adjacent edges of the coiled plate can be continuously welded. Welding machinery for such seaming of the pipe is commercially available. Welding is particularly advantageous for seaming heavy gauge pipe that can be made with the forming machine of this invention.

I claim:

1. A method for making corrugated pipe by helically winding a strip of a corrugated material about the axis of the pipe, the method comprising the steps of: feeding the strip to a pipe rolling station, engaging the strip with a plurality of strip supporting means on both sides of the strip over an extended, continuous length of the strip, deforming the strip with the supporting means by helically winding it about the axis, and moving the supporting means with the strip along a substantial portion of the helical'path prescribed by the strip as it is being deformed to thereby limit the friction forces between the strip and the support means.

2. A method according to claim 1 including the step of rolling the support means with respect to the strip to reduce frictional forces between them.

3. A method according to claim 1 including the step of engaging the strip with the support means at a point before any deformation of the strip takes place and continuing the engagement of the support means with the strip past a point where the strip has been fully helically deformed.

4. A method according to claim 1 including the step of cutting the length of the helically formed pipe by severing the strip at a point before its deformation by the support means along a line inclined with respect to the strip.

5. A method for making corrugated pipe by helically deforming a flat corrugated strip of material comprising the steps of: engaging a plurality of the strip corru gations at points at which the strip is flat with a plurality of laterally spaced ball sets comprising closely adjacent balls, first guiding the balls in each set engaged with strip corrugations along a straight path and thereafter guiding the balls in each set engaged with strip corrugations along a helical path corresponding to the desired helical deformation of the strip to form the pipe, and maintaining the balls in engagement with the strip to thereby helically deform the strip while the strip portion being deformed is substantially homogeneously supported by the closely adjacent balls in the sets.

6. Apparatus for forming corrugated pipe from corrugated strip material comprising: a plurality of opposing, laterally spaced ball raceways including strip engaging portions for the simultaneous contact between the balls and both sides of the strip corrugations, the portions having a compound curvature for deforming the strip into a helically coiled strip when the strip is advanced past the portions, and means for joining adjacent edges of the helically coiled strip to thereby construct the corrugated pipe.

7. Apparatus according to claim 6 including means for severing the strip prior to its deformation along a diagonal line to thereby cut the manufactured pipe to the desired length.

8. Apparatus for making corrugated pipe from flat strips of corrugated materials by helically winding the strip about the pipe axis comprising: rigidly mounted jaws through which the strip is passed, means carried by the jaws for guiding a multiplicity of closely adjacent balls into rolling engagement with fiat strip corrugations along a straight path of limited length and thereafter along a compoundly curved path while the balls are so engaged which causes the initial deformation of the strip while engaged and supported by the balls to prevent buckling of the strip and a helical coiling of the strip to the diameter of thepipe, and means for feeding the strip between the jaws and past the balls to thereby rollingly engage the strip and the balls.

9. Apparatus according to claim 8 including lubricating means comprising manifold means connected with the tubular guides for the discharge of a lubricated air mixture into the guides to thus lubricate the balls and remove foreign materials from the guides.

10. Apparatus according to claim 8 including means permitting a limited adjustment of the curvature of the ball guide means for varying and precisely setting the diameter of the finished pipe.

11. Apparatus according to claim 8 including means for adjusting the spacing between the jaws.

12. Apparatus according to claim 8 including means permitting rotation of the finish formed pipe as it is being formed, and further including means for seaming adjacent edges of coiled corrugated strip, the seaming means being positioned so that ball guide means are disposed on each side of the seaming means for continued guidance of portions of the finish formed and seamed pipe during the manufacturing process while the tube rotates about its axis.

13. A corrugated pipe making apparatus comprising: a frame, means for feeding corrugated strip material towards a forming station, rigid spaced apart cross bars positioned at the forming station, secured to the frame and extending past sides of the strip, first ball raceway means carried by one of the cross bar for engaging a side of the strip that ultimately forms an exterior side of the pipe with a plurality of balls movable in and guided by the first raceway means, the first raceway means including means guiding the balls from an engagement point aligned with corrugations of the nondeformed strip to a disengagement point along a compoundly curved path which causes the helical deformation of the strip to yield pipe of the desired diameter, second ball raceway means carried by the other cross bar for engaging another side of the strip that ultimately forms an interior side of the pipe with a plurality of balls movable in and guided by the second raceway means, whereby actuation of the feeding means causes passage of the strip past the raceways and the desired helical deformation of the strip into corrugated pipe through its rolling engagement with the balls.

14. Apparatus according to claim 13 wherein the raceway defining means comprises a plurality of ball guidance members secured to the cross bar and spaced in a lateral direction a distance equal to the spacing of the strip corrugations, the guidance members including a partially open portion extending at least over the compoundly curved length of the ball path for engagement of the strip corrugations by balls in the open guidance member portion.

15. Apparatus according to claim 13 including means initially engaging the balls in the raceways with the strip corrugations at a point prior to a point at which the strip begins to be deformed.

16. Apparatus according to claim 15 including means for adjusting the curvature of the compoundly curved opened guide means portion in at least one direction to permit limited adjustments in the pipe size being formed.

17. Apparatus according to claim 13 wherein the second ball raceway means comprises a plurality of second ball guidance members secured to the second cross bar for continuously circulating balls into rolling engagement'with strip being helically deformed and for rigidly guiding the strip during such deformation, the second guidance member being offset with respect to the first guidance member.

18. Apparatus according to claim 17 wherein the second guidance members are offset with respect to the first guidance members by one-half the distance befor removing foreign particles from the raceways and for lubricating the balls in the raceways.

22. Apparatus according to claim 13 including means for adjusting the spacing between the first and second cross bars and means for firmly locking the adjusted cross bars to each other for their subsequent use without additional adjustments.

23. Apparatus according to claim 21 wherein the frame includes disengageable means determining the position of the interlocked cross bars with respect to the undeformed strip and the frame, and means for firmly securing the interlocked cross bars as positioned by the positioning means to the frame.

24. Apparatus according to claim 23 including a set of interlocked cross bars for each desired pipe size, and wherein the positioning means includes means for positioning each neck cross bar set at a predetermined relative angularity with respect to the frame which yields the desired pipe diameter upon deformation of the strip.

Claims

1. A method for making corrugated pipe by helically winding a strip of a corrugated material about the axis of the pipe, the method comprising the steps of: feeding the strip to a pipe rolling station, engaging the strip with a plurality of strip supporting means on both sides of the strip over an extended, continuous length of the strip, deforming the strip with the supporting means by helically winding it about the axis, and moving the supporting means with the strip along a substantial portion of the helical path prescribed by the strip as it is being deformed to thereby limit the friction forces between the strip and the support means.

5. A method for making corrugated pipe by helically deforming a flat corrugated strip of material comprising the steps of: engaging a plurality of the strip corrugations at points at which the strip is flat with a plurality of laterally spaced ball sets comprising closely adjacent balls, first guiding the balls in each set engaged with strip corrugations along a straight path and thereafter guiding the balls in each set engaged with strip corrugations along a helical path corresponding to the desired helical deformation of the strip to form the pipe, and maintaining the balls in engagement with the strip to thereby helically deform the strip while the strip portion being deformed is substantially homogeneously supported by the closely adjacent balls in the sets.

8. Apparatus for making corrugated pipe from flat strips of corrugated materials by helically winding the strip about the pipe axis comprising: rigidly mounted jaws through which the strip is passed, means carried by the jaws for guiding a multiplicity of closely adjacent balls into rolling engagement with flat strip corrugations along a straight path of limited length and thereafter along a compoundly curved path while the balls are so engaged which causes the initial deformation of the strip while engaged and supported by the balls to prevent buckling of the strip and a helical coiling of the strip to the diameter of the pipe, and means for feeding the strip between the jaws and past the balls to thereby rollingly engage the strip and the balls.

13. A corrugated pipe making apparatus comprising: a frame, means for feeding corrugated strip material towards a forming station, rigid spaced apart cross bars positioned at the forming station, secured to the frame and extending past sides of the strip, first ball raceway means carried by one of the cross bar for engaging a side of the strip that ultimately forms an exterior side of the pipe with a plurality of balls movable in and guided by the first racEway means, the first raceway means including means guiding the balls from an engagement point aligned with corrugations of the non-deformed strip to a disengagement point along a compoundly curved path which causes the helical deformation of the strip to yield pipe of the desired diameter, second ball raceway means carried by the other cross bar for engaging another side of the strip that ultimately forms an interior side of the pipe with a plurality of balls movable in and guided by the second raceway means, whereby actuation of the feeding means causes passage of the strip past the raceways and the desired helical deformation of the strip into corrugated pipe through its rolling engagement with the balls.

17. Apparatus according to claim 13 wherein the second ball raceway means comprises a plurality of second ball guidance members secured to the second cross bar for continuously circulating balls into rolling engagement with strip being helically deformed and for rigidly guiding the strip during such deformation, the second guidance member being offset with respect to the first guidance member.

18. Apparatus according to claim 17 wherein the second guidance members are offset with respect to the first guidance members by one-half the distance between strip corrugations.

19. Apparatus according to claim 17 wherein the second members include a compoundly curved, partially opened portion and wherein the first and second raceways include mouth sections which gradually move balls in the raceways towards each other until in firm engagement with both sides of the strip.

20. Apparatus according to claim 19 including a flying shear mounted to the frame for diagonally cutting the strip before it reaches the raceways to thereby limit the length of the manufactured pipe and form straight pipe ends.

21. Apparatus according to claim 20 including means for removing foreign particles from the raceways and for lubricating the balls in the raceways.