Multiple wire wrap screen fabrication method

A wire wrap screen manufacturing method for a given screen diameter involves simultaneous winding of parallel wires that begin in circumferentially offset locations on one end of a perforated base pipe that has circumferentially spaced support rods saves fabrication time. Each of the ends of the wires lie in a common plane to allow fitting an end cap for sealing or to just continuously weld at the ends of the wires to seal the assembly to the base pipe. The spot welds to the support rods occur as the wire is wound over such rods. Equal initial circumferential spacing of the start locations for the wires is preferred although asymmetrical spacing is preferred.

FIELD OF THE INVENTION

The field of the invention is a fabrication method for a wire wrap screen and more particularly a method to speed up fabrication time by winding and welding multiple adjacent wires at the same time.

BACKGROUND OF THE INVENTION

Wire wrap screens comprise a perforated base pipe having a plurality of spaced axially oriented rods over which a wire generally having a trapezoidal cross section is wrapped continuously and spot welded to the rods as the winding process continues. Fairly sophisticated machines such as illustrated in FIG. 2 of US 2005/0125980 are used to wrap the single wire around the axially oriented rods to make a screen that is of a particular diameter. As is also illustrated inFIG. 5of this reference, nested wire wrap screens of different dimensions can be produced at the same time with a single wire feed going on at the same time for constructing the screens that have different outside diameters. Even when building nested screens at the same time, each screen is assembled with a single wire feed. This is a rather slow process that could require as much as 90 minutes for the fabrication of 20 feet of screen. The fabrication process involves feeding wire on a rotating hub of a base pipe with spaced axially oriented rods and spot welding the wire to the rods periodically to maintain the wire spacing on the wraps. It is the wire spacing that determines the particle size that will be retained on the wires when the finished screen is in use.

Other techniques called pre-pack put a filtering layer under the wire wrap as illustrated in U.S. Pat. No. 5,190,102. Other manufacturing techniques for wire wrap screens involve the use of expansion to assemble the wrapped wire and base pipe together as illustrated in U.S. Pat. No. 8,096,037.

What is needed and provided by the present invention is a production method for wire wrap screens that increases the manufacturing speed of such screens. This is accomplished with a feeding technique that feeds multiple wires that begin at circumferentially spaced locations so that for every revolution of the rotating hub assembly multiple windings of wire are applied and spot welded or otherwise attached. At the opposite end of the screen the individual wires are terminated at circumferentially offset locations similar to the initial end of the manufactured screen so that the ends may be transverse to the longitudinal axis to permit end sealing with caps to be welded or simply by welding the ends to the base pipe and rods that underlie the wire wrapping. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.

SUMMARY OF THE INVENTION

A wire wrap screen manufacturing method for a given screen diameter involves simultaneous winding of parallel wires that begin in circumferentially offset locations on one end of a perforated base pipe that has circumferentially spaced support rods saves fabrication time. Each of the ends of the wires lie in a common plane to allow fitting an end cap for sealing or to just continuously weld at the ends of the wires to seal the assembly to the base pipe. The spot welds to the support rods occur as the wire is wound over such rods. Equal initial circumferential spacing of the start locations for the wires is preferred although asymmetrical spacing is preferred.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1a base pipe10has a series of openings12. Support rods14extend axially and are shown at regular circumferentially spaced intervals with some of the rods14over the openings12and some avoiding the openings12. The openings12can be in rows as shown or randomly distributed to get the desired amount of open area for the anticipated flow through the screen at a desired pressure drop. The spacing of the rods14can also be variable in a circumferential direction but it is preferred that their orientation be aligned with a longitudinal axis of the base pipe10. Some angular variation from parallel to the base pipe10longitudinal axis is tolerable within about plus or minus 5 degrees.

The method comprises of winding multiple wires such as16and18at the same time with the desired spacing between them to define the size of the solids that are to be retained on the outside of the assembled screen. Instead of feeding a single wire onto a base pipe with rods14as in the past the present method takes multiple adjacent wires16and18and feeds them with a common pitch to maintain a constant spacing as the base pipe is rotated. As each wire crosses a support rod14a spot weld20can be initiated. The orientation is such that both wires such as16&18can be spot welded to a given support rod14at a time. Although two wires that are run adjacent to each other are illustrated, depending on the wire feeder design possibly more adjacent wires can be wound at the same time within the scope of the invention. Preferably the start of each wire is circumferentially offset from other wires being wound but starts in the same transverse plane perpendicular to the longitudinal axis of the base pipe10. Because of this an end cap (not shown) can be mounted to each end of the wire wrap to seal the end of the shape made by the wound wires to the base pipe or alternatively the end of the wires can be otherwise sealed to the base pipe10with continuous welding or by other means. The attachment of the wires to the rods14can be with resistance welding. The preferred wire cross-sectional shape is trapezoidal although other shapes such as round or quadrilateral are contemplated. The start locations and end locations of each of the multiple wires being run adjacent to each other at the same time is preferably even spaced circumferentially although other uneven spaces are contemplated. The multiple wires can be fed in the same plane and as contact is made with each successive wire14a resistance weld is formed.

The advantage of the method is shortening the time for fabrication of the same length of screen by a factor of how many wires are being fed at the same time.