Apparatus for and method of manufacturing helically wound structures

The present invention relates to an apparatus for and method of manufacturing helically wound structures and relates particularly to the manufacture of pipes and longitudinal structures formed by winding strips of metal in a helically overlapping relationship. Other structures such as storage vessels, towers and support structures may also benefit from features described herein.

Presently it is known to manufacture tubular structures by winding preformed metal strip onto a rotating mandrel such that the strip is deposited onto the mandrel in a self-overlapping manner and is retained in place by mechanical deformation of an edge thereof such that it interlocks with an adjacent edge, thereby to retain the strip in place on the final structure. EP0335969 discloses an apparatus for forming a helically wound tubular structure formed from a flat strip of metal wound onto a mandrel. The flat strip is fed from one or other of a pair of supply spools mounted concentrically with the axis of the tubular structure to be made. A rotating winding head is used to wind the strip onto the mandrel and includes a plurality of powered forming rollers which impart an initial form to the cross section of the metal strip before it is passed to a final set of rollers that lay the strip onto the mandrel and then swage over an edge of the strip so that it becomes mechanically locked to the previous layer over which it is wound. This is a complex process. Also provided is a mechanism for ensuring the strip supply is maintained constant and this mechanism includes speed control of the forming rollers. The coaxial supply bobbins are fed from an external supply spool so as to maintain the supply thereof. A welding station is used to join one end of the strip material to another without having to stop the machine.

It is also known to control the final diameter of the formed pipe by controlling a plurality of radius forming rollers immediately before the strip is wound into its final structure. Such an arrangement is disclosed in U.S. Pat. No. 3,851,376 which relates to a method and apparatus for forming a helical seam sealed metal pipe in which the spring back force of the material is controlled within permissible limits. A plurality of forming rollers are provided for this purpose and include a three roller arrangement of fixed rollers the position of which is selected and set to impart a desired radius of curvature to a metal strip as it passes through the rollers. An additional roller is displaceable in response to a feedback signal indicative of the spring back force so as to increase or decrease the forming force as necessary so as to ensure the spring back force is maintained within desired limits.

It is also known to elastically deform a metal strip and wind it into a self overlapping helically wound structure and employ an adhesive to maintain the strip in its final shape. Unfortunately, the strip retains its desire to return to its relaxed (flat) shape and the adhesive is necessary in order to prevent the strip delaminating and unwinding. Additionally, the final structure suffers from a high peel force created by the stresses within the plastically deformed strip and these put a great load on the adhesive itself, thereby compromising the structural integrity of the structure and limiting its pressure capacity significantly below its theoretical limit.

Whilst the above arrangements provide perfectly acceptable methods of manufacturing pipes they either rely on plastic deformation of an edge of the material strip to ensure the product stays together or must rotate the final product during the forming process, both of which can be problematic. For example, the force required to deform an edge of the metal strip as it is lain down onto a previously deposited layer and lock it thereto is significant. Additionally, such machines consume unnecessarily large amounts of energy and are very slow as operating such a deformation process at high speed is extremely difficult. The latter problem of having to rotate the product during forming limits the use of this arrangement to the production of relatively short sections of pipe and such sections must be joined if a long section is required. When laying trans-continental pipelines it is extremely undesirable to have to introduce any such joints as they tend to be expensive to incorporate and problematic in operation.

It is an object of the present invention to provide an apparatus for and method of manufacturing tubular structures which reduces and possibly overcomes some of the problems associated with the prior art.

Accordingly, the present invention provides an apparatus for manufacturing a tubular structure of helically wound strip comprising: a faceplate, mounted for rotation about a longitudinal axis; a drive mechanism, for driving the faceplate in a first direction about said longitudinal axis; and diameter defining rollers, mounted on said faceplate for causing the strip material to bend to a predetermined diameter prior to being formed into a tubular structure.

Preferably, the apparatus includes an assembly of shaping rollers, mounted for rotation with said faceplate and for forming a cross-sectional profile on strip material prior to it being formed to a pre-determined diameter. One or more of said shaping rollers may be driven rollers.

Preferably, the diameter defining rollers include three mutually confronting rollers, one of which is adjustable relative to the other two so as to cause any strip material passing between said rollers to adopt a radius of curvature defined by the positional relationship between said rollers.

In a particular arrangement the diameter defining rollers include a pair of pinch rollers rotatable about their own longitudinal axes and between which a strip of material may pass and a ring roller which is adjustable relative to a first pinch roller by rotation about the axis of the second.

In a most convenient arrangement the apparatus includes an actuator connected to said ring roller for effecting adjustment relative to said second pinch roller.

Advantageously, the apparatus may be provided with a reaction roller against which forming forces exerted on any strip as it is caused to adopt a radius of curvature by the ring roller will be reacted.

Preferably, the apparatus includes a second actuator for causing the axial position of the reaction roller to be varied relative to a pinch roller. An actuator may also be provided for effecting axial adjustment of one of said pinch rollers relative to the other.

Advantageously, the apparatus includes drive means for driving one or more of said diameter defining rollers.

In a particularly convenient arrangement the apparatus includes a computer coupled to said actuator or actuators for controlling the positional relationship of the roller or rollers. Said computer may comprise a computer programmed to control said roller or rollers in accordance with a predetermined programme.

Preferably, the apparatus includes a first gearing assembly mounted on said faceplate and driven from a fixed gear arranged coaxially with said faceplate and in which said first gearing assembly is engaged with said diameter defining rollers for driving said diameter defining rollers.

Conveniently, the apparatus further includes a second gearing assembly mounted on said faceplate and driven from a fixed gear arranged coaxially with said faceplate and In which said second gearing assembly is engaged with said forming rollers for driving said rollers. The apparatus may also include a main drive member for driving said faceplate in said first direction which may comprises a driven gear engaged with a corresponding gear portion on said faceplate.

Conveniently, the apparatus includes a stock support for supporting a supply of stock of strip material for being formed into a tubular structure. The stock support may comprise a circumferentially extending cassette extending around said faceplate on an outer diameter thereof.

Conveniently, said cassette comprises a plurality of support rollers circumferentially spaced around the longitudinal axis and which cooperate with a portion of a supply of strip stock and allow said stock to rotate about said axis. Said support rollers may be mounted for rotation about a spindle secured to a non rotating portion of said assembly.

In a particular arrangement the forming rollers are staggered along said longitudinal axis and in which the axis of rotation of said rollers relative to said axis varies in accordance the spiral angle of the trip as it passes from a supply thereof to said diameter defining rollers.

Conveniently, the apparatus may include a first strip supply guide roller for guiding a supply of strip material from a store thereof to said forming rollers. The apparatus may also include a second strip supply roller for guiding a supply of formed strip from said diameter defining rollers to an inner diameter at which a tubular member is to be formed.

Advantageously, the apparatus includes an adhesive applicator for applying an adhesive onto at least a portion of any strip after it passes through said diameter forming rollers. Said adhesive applicator may comprise an adhesive storing cassette for storing a roll of adhesive strip. Said adhesive storing cassette may include a spindle mounted on said faceplate for rotation therewith and around which a supply of adhesive strip may be positioned and rotate upon application of said adhesive strip to said tubular structure forming strip.

The apparatus may further include a backing removing mechanism for removing any protective backing on said adhesive strip prior to said adhesive strip being applied to the tubular structure forming strip.