Method Of Making A Tubular Member By Helically Coiling A Metallic Strip, Tubular Member Produced By This Method And Device For Carrying Out This Method

Abstract

A strip having hooked edges is laterally curved and coiled into a spiral in which the hooked edges of adjacent coils overlap. Just before the coils are overlapped the strip is formed into a helix the turns of which slant in a direction opposite to that of the turns of the helix finally formed so that when adjacent turns are forced into engagement with each other adjacent turns are resiliently biassed toward each other. The invention includes apparatus adapted to carry out this method and the tubular member produced thereby.

Description

SUMMARY OF THE INVENTION

This invention relates to a new method of manufacturing tubular articles by helically winding a shaped metallic strip, to the new tubular members produced by this method, and to the apparatus used in carrying out said method.

It is the object of the present invention to provide tubular members made by the simple interfitting of shaped metallic strips and which have the characteristic of possessing both great mechanical strength and a substantial flexibility so that the tubular members may be wound up on cores of relatively small diameter.

The tubular members according to the invention may be advantageously used as flexible drill pipe in the drilling of oil wells.

When flexible drill pipe is used for this purpose a bit is mounted at the end of a long tubular member having a certain flexibility, and driven either by an electrical motor at the head of the well, and supplied through electrical cables passing down through the tubular member, or by a turbine driven by a fluid such as the mud which is forced under pressure into the flexible tubular member.

The great advantage presented by this new drilling process resides in the fact that it is unnecessary to rotate the tubular member about its axis as it is progressively introduced into the ground, as is the case in conventional drilling methods.

Moreover, the fact that the tubular member is flexible makes it possible to roll it up easily on drums of relatively small diameter. This considerably facilitates the operations of sending down and withdrawing tubular members which are always necessary for the maintenance and repair of drilling bits.

The cylindrical members used for flexible drilling generally comprise an internal tube of plastic material which seals the tubular member against fluids which pass therethrough and provides a smooth inner surface which facilitates the flow of fluids. This internal tube must be located inside an equally flexible tubular member which is capable of resisting the substantial mechanical stresses resulting from the high pressures which must prevail inside and outside the tubular member during drilling. This flexible tubular member may be made, in accordance with the invention, from a helically coiled shaped metallic strip.

The tubular members according to the invention are then, in the case of flexible drilling tubes, covered by layers of wire wound thereabout, as in the case of cables, to insure the mechanical strength and resistance to tension which are required.

The present invention proposes to provide tubular members which, while sufficiently flexible, have a substantial mechanical strength so as to be capable of resisting both internal and external pressure. Moreover, the tubular bodies according to the invention may be easily formed directly around the tube which is to constitute a fluid-tight seal.

The manufacture of tubular members of the type according to the invention from strong shaped steel strips has already been suggested, using strips having the general form of a Z or an S.

However, it has not heretofore been possible to helically wind such shaped strips under satisfactory conditions.

It has been found, in effect, that when an attempt is made to helically wind a strip having an S or Z section by conventional methods the cohesion between the turns of the resulting tubular member is insufficient. This results in poor mechanical strength, which renders such a tubular member completely unsuitable for use as flexible drilling pipe.

It is the object of the present invention to provide a new process for manufacturing a flexible tubular member adapted to be used as flexible drilling pipe from a strong shaped steel strip having an S or Z section. In accordance with this method a permanent arcuate deformation is imparted to the strip, so that the edge of the strip which, after manufacture of the tubular member, is outside the tubular member, is longer than the edge of the strip which, after manufacture of the tubular member, is inside thereof. After having first deformed the metallic strip in this manner, it is helically deformed to form the tubular member by engaging one edge of the strip over the edge of the last-formed turn of the tubular member. This process is characterized by the fact that the strip is given a shape such that it is resiliently biassed against the last-formed turn of the tubular member.

For this purpose the shaped strip is given a natural helical shape in a direction opposite to that in which the tubular member is being formed.

The present invention is also directed to the new article of manufacture which consists of a tubular member made by helically winding a strong, shaped metallic steel strip having an S or Z shaped section in accordance with the foregoing process, said tubular member being principally characterized by an excellent resistance to internal and external pressure, by substantial flexibility which permits it to be wound on cores of relatively small diameter, and a perfectly cylindrical shape which it retains while being bent.

The present invention also relates to the new article of manufacture which consists of a flexible tube for use in drilling oil wells essentially characterized by the fact that it comprises a strong flexible tubular steel member as above defined.

The present invention is also directed to a device for carrying out the foregoing process, which device is essentially characterized by the fact that it comprises in combination: means for bringing the shaped metallic strip at a suitable speed into a plane substantially tangent to the tubular member which is being formed; means for imparting a permanent arcuate deformation to said strip, the side of the strip located in the direction in which the tubular member is being formed having a length greater than the other side of the strip; means consisting, for example, of forming fingers for imparting to said strip a helical deformation about a diameter which corresponds substantially to the diameter of the tubular member, thus assuring the engagement of the coil being formed with the coil which has just been formed; means for guiding the tubular member formed in this manner, and means for synchronizing the rotation of the tubular member which has been formed and the arrival of the strip from which the tubular member is to be made.

The means for imparting an arcuate deformation to the strong steel strip may advantageously consist of a set of rollers bending the strip beyond its elastic limit.

In one particular embodiment of the invention, the means for imparting a helical shape to the strip may advantageously consist of a forming head having a plate mounted through a universal joint on a framework so as to be adjustable in its operating position by swinging it about both a horizontal axis and a vertical axis.

This plate comprises a central orifice through which the tubular member is formed. About the periphery of this orifice are means such as T shaped notches to which the supports for the various forming fingers may be attached.

In one embodiment of the invention the supports for the forming fingers make it possible to regulate the angular orientation of the fingers with respect to a direction radial to the tubular member and the distance of the fingers from the axis of the tubular member being formed.

Other properties and characteristics of the invention will appear in the course of the following description of a preferred embodiment of the invention, which is being given purely by way of example, and with reference to the accompanying drawings, in which:

FIG. 1 is a schematic elevational view of a machine for carrying out the process according to the invention;

FIG. 2 is a top plan view of the machine of FIG. 1;

FIG. 3 is a schematic perspective view showing how the shaped memallic strip is formed into a helix in accordance with the invention;

FIG. 4 is a partial sectional view of an enlarged scale taken through the axis of a tubular member manufactured in accordance with the invention;

FIGS. 5, 7 and 9 are elevational view taken transversely of the axis of a tubular member, and FIGS. 6, 8 and 10 are corresponding side views taken during various steps of the formation of the tubular member according to the invention;

FIG. 11 is an elevational view taken transversely with respect to the axis of the tubular member, showing the forming fingers and their supports; and

FIG. 12 is a schematic sectional view taken along the line 12--12 of FIG. 11.

FIGS. 1 and 2 show the overall layout of a machine for carrying out the process according to the invention. In particular, these figures show a reel 1 on which a tube of plastic material 2 is wound. This tube is intended to constitute the inner lining of the tubular member according to the invention. The reel 1 is mounted on a support 3 which rotates about a horizontal axis.

Another reel 4 carries the tubular member 5 according to the invention and is mounted on a support 6 which also rotates about a horizontal axis.

The reel 4 is rotated with respect to the support 6 by a motor 7 through a conventional transmission 8, which is schematically shown.

The shaped high strength steel strip 9 is unwound from a reel 10 rotatably mounted on a stationary support. This shaped strip 9, driven by two pairs of rollers 11, reaches the forming head 12 after having passed over the rollers 13 which impart an arcuate shape to it. The device for curving the shaped metal strip is shown on the other figures in a more detailed manner. Beyond the forming head the shaped strip 9 is converted into the tubular member 5 which then passes through a traction cage 14 which rotates about a horizontal axis and comprises driving rollers 15 which engage the tubular member 5 and drive it along an axial path.

An electric motor 16 drives a shaft 17 through a set of pulleys and belts. This shaft extends the full length of the machine and controls, through reduction gearing 18 and belts or chains, the horizontal rotation of the support 6.

It also controls, through reduction gearing 19, the rotation of the traction cage 14, and through reduction gearing 20, the rotation of the rollers 15 which axially advance the tubular member.

Similarly, the shaft 17 controls through reduction gearing 21 the rotation of the pairs of rollers 11 which axially advance the strip 9. Finally, the shaft 17 drives the cage 3 through reduction gearing 22.

A brake 23, which is only schematically shown, restricts the unwinding of the plastic tube 2 which is coiled on the reel 4, after having been encased in the tubular member manufactured in accordance with the invention.

The speeds of rotation of the different members which have been described are so determined as to coordinate the speed of rotation of the tubular member 5 and the speed at which the strip 9 advances to form the member 5 in question.

The different components to which reference has been made have not been individually described in a more detailed manner because these components, when considered individually, are well known in the cable manufacturing industry.

The device for carrying out the process according to the invention is shown in a more detailed manner on the perspective view of FIG. 3.

This figure shows the two pairs of rollers 11 which drive the strip 9 at a suitable speed. The section of this strip is shown on a larger scale at the left of FIG. 3.

The rollers 11 have shapes such that the strip 9 is lead flat to the table 24, which is provided with two forming rollers 13.

The axes of these rollers are mounted so that they turn freely and their positions may be adjusted by screw means 25, which are schematically shown. These rollers 13 cooperate with a third roller 26 designed to turn the strip 9 toward the forming head.

The forming head, which is indicated as a whole by reference numeral 12, consists of a plate 27 mounted by means of a universal joint on a support 28.

This universal joint mounting permits the plate 27 to pivot on two arms 29 about a horizontal axis 30. The plate 27 is attached to the arms 29 by screws 31 seated in arms 29 and passing through semicircular holes 32 in a member fixed to the plate 27.

This arrangement permits the position of the plate 27 to be easily adjusted by pivoting it about the horizontal axis 30.

A second adjustment of the plate 27 with respect to a vertical axis results from the fact that the arms 29 are connected to each other by a cross member 33 which is provided with oblong holes 34 through which the bolts 35 which attach the cross member 33 to the base 28 pass.

It will be understood that, under these conditions, by releasing the bolts 35, it is possible to pivot the cross member 33 slightly and thus turn the plate 27 about a vertical axis.

Finally, the cross-member 33 is mounted on bolts 35 between adjustable nuts which make it possible to adjust the height of the plate 27.

The plate 27 (which, as has already been explained, may be adjusted in all directions) comprises a central hole 36. The tubular member 5 which is formed by the strip 9 passes through this hole.

The plate 27 comprises a groove 37 encircling the orifice 36. This groove has a T shaped section and receives the heads of the bolts 38 by means of which the supports 39 for the forming fingers are attached. In the present case these supports 39 are four in number, but may be more or less in number.

Each support is attached to the plate 27 by bolts 38 which pass through elongated orifices of circular shape in the supports 39 so that the latter may be angularly adjusted in a radial plane with respect to the plate.

In like manner the supports 39 which carry the forming fingers 40 may be adjusted in an axial direction by threaded rods 40a.

It will be seen that under these conditions, as many forming fingers as desired may be mounted and each of these fingers may be set in any position necessary to obtain satisfactory regulation of the machine.

FIG. 3 also shows that the circular groove 37 communicates with a lateral groove 37a through which the bolts 38 may be introduced.

FIGS. 11 and 12 are two views showing the forming fingers 40 and the adjacent parts of the machine on a larger scale. Thus FIG. 11 shows the part of supports 39 for the forming fingers 40.

FIG. 12 shows schematically in section the tubular member 5 which is being made from a strip which, in the present case has a very schematic S shape, and the profile of the forming finger 40 corresponding to this specific shape of the strip 9.

FIG. 4 shows in section on a larger scale the upper part of a tubular member according to the invention made from a strip having a different shape.

In this case the strip 9 has a generally S shape having two hooked edges 9a and 9b which are connected to the main part of the strip 9 by grooved portions 9'a and 9'b.

As seen on FIG. 4, the formation of the tubular body is such that a hooked edge 9a of a coil engages in the grooved part 9'b of the next coil while leaving a little play between the two hooked edges 9a and 9b which engage each other.

As will be hereinafter explained, these coils are preferably so formed that the coils have a tendency to press resiliently against each other. It follows that the edge of each coil 9b bears resiliently against the vertical flank of the recess 9'a or 9'b of the adjccent coil while leaving the unoccupied space 41 clearly shown on FIG. 4.

It is because of the existence of this space 41 that the tubular member according to the invention has an exceptional flexibility. In effect, as may be seen on FIG. 4, it is possible by imposing a sufficient force to overcome the elastic force which holds the two coils together, to bring two adjacent coils into contact through only the two projecting hooked members 9a and 9b.

It will thus be seen that due to the space 41, which leaves a certain play between the coils, it is possible to impart to the tubular member according to the invention a relatively great flexibility. However, according to the preferred embodiment of the invention, the coils are resiliently urged against each other so that the tubular member according to the invention has a tendency to spontaneously return to its straight form.

The method of making the helical coil of the strip 9 in accordance with the preferred embodiment of the invention will now be described.

FIGS. 5 and 6 show the first step in the formation of the helical coil according to the invention.

FIG. 5 is an elevational view transverse to the axis of a tubular member being formed, and shows the profile of the first coil. In order to make this, the shaped strip 9 arrives along a straight path 42 after passing through the forming rollers which have imparted a curved shape thereto as may be clearly seen in FIG. 6. The forming fingers impose on the part 42 which advances in the direction of the arrow F a resilient curvature at 43, which results in a permanent deformation at 44 corresponding substantially to the diameter of the tubular member which is being manufactured.

As may be clearly seen on FIG. 6, the arcuate deformation which is imparted to the strip 9 is such that the strip is spontaneously helically wound toward the bottom of the FIG. 6 (arrow F1) in the form of a helix having coils which are not connected to each other.

In order to produce the tubular member according to the invention, the part 44 of the strip 9 is caused to cross the first loop formed not below, but above (FIG. 6). This begins the coil which is shown in FIG. 8.

It will, however, be appreciated that because of the natural shape of the coil which is formed when the helix is forcibly coiled upwardly, while this helix would be formed spontaneously in a downward direction, the part 44 of the coil which forms (FIG. 8) is elastically urged against the part 42 which forms the previous turn.

FIGS. 9 and 10 show the evolution of the formation of the tubular member upwardly and it will be seen that when the member 44 has been passed above the part 42 (FIG. 8), the helical shape which results must necessarily continue to be formed in this direction (FIG. 8, FIG. 10).

This results in the formation of a tubular member 5 in which the different turns engage each other as has been clearly explained with reference to FIG. 4, while the turns are urged elastically against each other by reason of the phenomen which has just been described.

It will also be appreciated that the degree of force by which the different turns of the spiral are urged against each other may be regulated by regulating the directions and magnitudes of the deformations imposed upon the strip.

The tubular members which are made in accordance with the invention have particularly valuable properties for numerous applications, and especially in the case of flexible tubing for use in drilling oil wells.

It is particularly easy to form the flexible tubular member about the tube of plastic material which is designed to make it fluid-tight.

In like manner, the tubular member has the advantage of offering a great resistance to internal and external pressures even though being very flexible, which makes it possible to wind the tubular members according to the invention on cores of sufficiently small diameter to make them easy to transport and handle.

It will of course be appreciated that the embodiment which has just been described has been given purely by way of example and may be modified as to detail without thereby departing from the basic principles of the invention.

In particular, it is clear that the sections of the strong steel strip which have been shown on the drawings have been given only by way of example, and the strip may be given other shapes depending upon the nature and characteristic of the tubular member which is to be manufactured.

Claims

What is claimed is:

1. Method of manufacturing a flexible tubular member by coiling a metallic strip having longitudinally extending abutment means into a helix having overlapping turns, which method comprises the steps of imparting an arcuate deformation to said strip such that the edge of said strip which is to be on the outside of the overlapping turns in the completed tubular member is longer than the edge of the strip which is to be on the inside thereof, coiling said strip into a helix in which, when said helix is a axially unstressed, the turn last formed lies on one side of the preceding turn, and stressing said strip by positioning the last-formed turn on the other side of said preceding turn, with the portion of the of the longitudinal abutment means in each turn contacting a surface on an adjacent turn to resist a return of said strip to its unstressed position.

2. Method as claimed in claim 1 in which, when said helix is axially unstressed, the shorter edge of the section of said strip defining said last-formed turn lies close to the longer edge of the section of said strip defining the preceding turn, and the longer edge of the strip defining said last-formed turn is adjacent the shorter edge of the section of said strip defining said preceding turn when said helix is axially stressed.

3. Method as claimed in claim 1 in which the edges of said strip are hooked in opposite directions and the adjacent edges of adjacent turns are hooked over each other to resist separation of said turns axially of said tubular member.

4. Method as claimed in claim 1 according to which said strip is made of strong steel.

5. Method as claimed in claim 1 according to which the tubular member is formed about a plastic tube.

6. Flexible tubular member in the form of a helical coil having overlapping turns made from an arcuate metal strip, one edge of which is longer than the other, said strip comprising longitudinally extending abutment means, and being under an internal tension biassing the shorter edge of each turn of said coil toward the adjacent longer edge of an adjacent turn until the abutment means of each turn engages a cooperating surface on an adjacent turn with a force sufficient to cause said turns to reverse their relative positions axially of said coil if said reversal were not prevented by said engagement.

7. A tubular member as claimed in claim 6 encircling a fluid-tight tube and adapted for use in drilling oil wells.

8. Device for forming a flexible tubular member from a metallic strip of material having longitudinally extending abutment means which comprises in combination, means for leading the strip along a plane substantially parallel to the axis of the tubular member which is to be formed, means for imparting a permanent arcuate deformation to said strip such that the edge of the strip in the direction in which the tubular member is being formed is longer than the other edge of the strip, means for imparting a helical deformation to said strip to form it into a helix having a diameter substantially equal to that of the member being formed, and for engaging the longer edge of the turn being formed with the turn which has just been formed, means for guiding the tubular member thus formed, and means for synchronizing the speed of rotation of the tubular member being formed and the feed of the strip from which the member is to be formed.

9. Device as claimed in claim 8 in which the means for imparting an arcuate deformation to the strip comprises a set of rollers which bends said strip beyond its elastic limit.

10. Device as claimed in claim 8 in which the means for forming the strip into a helix comprises a forming head including a plate mounted on a universal joint so that its position m be adjusted about both a horizontal and a vertical axis.

11. Device as claimed in claim 10 in which the plate comprises a central orifice through which the tubular member is being formed and that the forming fingers are positioned on the periphery of this orifice by supports which are angularly and longitudinally adjustable.

12. Flexible tubular member as claimed in claim 6 in which the edges of said strip are hooked in opposite directions and the adjacent edges of adjacent turns are hooked over each other to resist separation of said turns axially of said tubular member.

13. Device as claimed in claim 8 in which said means for imparting an arcuate deformation to said strip imparts said arcuate deformation in a plane passing through both edges of the strip.