Abstract:
An apparatus for manufacturing wire wrapped screens utilizing a wire and support ribs is provided. The apparatus employs welding pressure control, utilizing a welding device mounted on a support assembly, wherein the support assembly is moveable in relation to a mounting structure and the wire and support rib weld pieces. Welding pressure is determined by a force measurement device, and a control and feedback system adjusts pressure. Mechanical actuator cylinders mounted on the support assembly and the mounting structure provide load balance. A method for making wire wrapped screens is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/889,185 filed on Oct. 10, 2013, which application is incorporated herein by reference as if reproduced in full below. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     FIELD OF THE INVENTION 
     The present invention relates to wire wrapped screens used during the production of oil, gas, and liquids. More particularly, the present invention relates to apparatus and methods of manufacturing wire wrapped screens. 
     BACKGROUND 
     Hydrocarbons are produced by drilling into subterranean hydrocarbon-bearing formations. Producing unconsolidated formation walls can result in sand or silt accumulating in the wellbore, which can ultimately cause various problems in the drilling operation. For instance, accumulated sand and rock particles may plug the wellbore formation, resulting in reduced production. Over the years, many methods of preventing sand from entering the wellbore along with the hydrocarbons have been developed, including gravel packing and use of sand screens. Sand control has become increasingly important in the industry. 
     Gravel packing is a commonly used method to keep formation sand in place and out of the well stream. Gravel packing entails placing a perforated base pipe or a well screen into the wellbore and packing the surrounding annulus with gravel of a desired size. The gravel serves as an additional filter medium to keep sand and fine particulates out of the production stream and provides support to the surrounding formation walls to prevent collapse. 
     Well screens used in sand control applications can be of various types, including wire mesh and continuous slot wire wrapped. Continuous slot wire wrapped screens are composed of wire helically wrapped around multiple support ribs to form a cylindrical screen with a continuous helical slot. It is important that slot size is maintained within determined tolerances throughout the length of the screen. 
     Wire wrapped screens are typically manufactured using wire wrapping machines that simultaneously wrap and weld the wire around multiple support ribs to form a hollow cylindrical well screen of a desired length. A spindle rotates the ribs causing wire to be wrapped around the set of ribs. 
     An important aspect of the manufacturing process is consistent, uniform welds. The present invention provides an improved apparatus and method for maintaining consistent weld pressure during the welding process at faying surfaces of the wrap wire and the ribs. 
     BRIEF SUMMARY OF THE INVENTION 
     A welding pressure control apparatus and method for a wire wrapping system comprises a welding device mounted on a welding support assembly. The support assembly is moveable in relation to a mounting structure and the weld pieces. Mechanical actuator cylinders mounted on the support assembly and the mounting structure provide load balance. A force measurement device indicates support assembly force transmitted to the welding device. A control and feedback system utilizes the force information to adjust welding pressure. Other characteristics and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the embodiments of the invention, reference is now made to the following Detailed Description of the Invention, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an illustrative view of a wire wrapping system with a pressure control assembly of the present invention. 
         FIG. 2  is a partial view of a mounting structure of the present invention. 
         FIG. 3  is a partial side view of a welding support assembly and mounting structure of the present invention. 
         FIG. 3A  is a partial side view of a rotating spindle of the present invention. 
         FIG. 4  depicts an embodiment of a method of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein like reference characters designate like or similar parts throughout,  FIG. 1  depicts a wire wrapping system  2  having a welding pressure control assembly  10 . Wire wrapping system  2  is used to manufacture wire wrapped well screens  18 . Wire wrapping system  2  includes a wire feed assembly  4 , bed  6 , control module  8 , welding pressure assembly  10 , headstock  12 , rotating spindle  14 , and tailstock  16 . 
     A plurality of elongated support ribs  20  and wire  22  are used to form screen  18 . Screen  18  may be formed around a pipe (not shown), or screen  18  may be formed as a generally hollow structure without a pipe being present during formation, as is depicted in  FIG. 1 . Wire  22  is wrapped helically around the support ribs  20  and is welded at each contact point  24  to a rib  20 . In this context, welding includes fusion welding, such as, but not limited to, electrical resistance welding. In an exemplary embodiment, welding is performed by a rotating welding wheel electrode  46  provided proximate headstock  12 . The welding wheel electrode  46  welds each wire  22  to corresponding ribs  20  at contact points  24  by electrical resistance welding. 
     Headstock  12  is equipped with a rotating spindle  14 . Spindle  14  rotates about axis A-A. Spindle  14  has a plurality of radially spaced rib openings  26  (shown in  FIG. 2 ) through which ribs  20  extend. Openings  26  are spaced from spindle axis A-A at various distances and in patterns to allow multiple circular patterns of openings  26 . In an exemplary embodiment, spindle  14  contains multiple circular patterns of openings  26  to allow construction of various diameters of screen  18 . 
     Openings  26  allow ribs  20  to extend generally along axis A-A but spaced therefrom prior to welding. Other supports (not shown) intermediate headstock  12  and tailstock  16  support ribs  20  substantially parallel to and equally spaced from axis A-A after welding, if a screen  18  is being formed without a pipe disposed there within. 
     Ribs  20  each have a first rib end  21  extending toward tailstock  16 . A tailstock spindle  30  grasps proximate rib ends  21  with a grasping mechanism (not shown) such as a pull ring or a chuck. Tailstock spindle  30  rotates about axis A-A. 
     Spindle  14  and tailstock spindle  30  are each driven to rotate about axis A-A by a servo motor (not shown). The servo motors driving spindle  14  and spindle  30  are each electronically connected to a processor  9 , which may be part of control panel  8 . Rate of rotation may therefore be controlled by processor  9 . 
     Head  66  is fixedly attached to spindle  14  and extends outward from the spindle  14  in the direction of the tailstock  16 . As shown in  FIG. 3A , head  66  has cylindrical openings (not shown) with milled longitudinal slots  15  sized and located to support ribs  20  and maintain rib  20  spacing. Head  66  serves as a support for ribs  20  and wire  22  during welding and comprises an electrode of the welding process. Head  66  may be of differing sizes for different screen  18  diameters. In one aspect wherein screen  18  is to be formed around a pipe, spindle  14  includes a centralized opening (not shown), in lieu of head  66 , through which the pipe extends. Tailstock spindle  30  grasps the end of the pipe extending through spindle  14  with a grasping mechanism (not shown). 
     Headstock  12  is disposed proximate first bed end  7  of bed  6 . Bed  6  is an elongate structure that extends along a longitudinal axis substantially parallel to, but offset from, axis A-A. Tailstock  16  is moveable along bed  6 . Movement of tailstock  16  may be controlled by a conventional linear drive mechanism, such as a ball screw drive. In an exemplary embodiment of the present invention, tailstock  16  is moved and controlled by an induction linear guide. The driver (not shown) controlling movement of tailstock  16  is electronically connected to processor  9  to allow controlled movement of tailstock  16  along bed  6 . 
     Wire feed assembly  4  is positioned proximate headstock  12 . Wire feed assembly  4  includes a rotating wire feed spool  32  and wire guide  36 . Wire guide  36  directs wire  22  toward support ribs  20 . 
     Referring to  FIG. 2  and  FIG. 3 , welding assembly  10  is located proximate bed  6 . Welding assembly  10  comprises a welding arm  38  positioned on welding support assembly  40  moveably positioned above bed  6 . Support assembly  40  is supported by a mounting structure  42 . Welding arm  38  is rotatable in relation to support assembly  40 . A section of welding arm  38  extends through support assembly  40  and a section of welding arm  38  extends from support assembly  40  toward headstock  12 . Welding wheel electrode  46  is mounted on welding arm  38  intermediate support assembly  40  and headstock  12 . A welding wheel assembly (not separately labeled), which includes welding arm  38 , is mounted to the bottom surface of support assembly  40  extending downwardly therefrom. The welding wheel assembly supports welding arm  38 . 
     Mounting structure  42  is supported on headstock  12  and is laterally moveable parallel to axis A-A. In an exemplary embodiment as shown in  FIG. 1 , lateral movement of mounting structure  42  is controlled by a servo motor  76  mounted on headstock  12  driving a ball screw shaft  78 . Guides  82 , mounted to mounting structure  42 , interact with ball screw shaft  78  resulting in controlled lateral movement of mounting structure  42  responsive to operation of servo motor  76 . Servo motor  76  is electronically connected to processor  9  of control panel  8  to provide controlled operation of servo motor  76  and consequent lateral movement of mounting structure  42 . 
     Welding wheel electrode  46  rotates on an axis of rotation depicted as B-B in  FIG. 1  and  FIG. 3 . Axis B-B is parallel to, but offset from, axis A-A. In an exemplary embodiment of the present invention, welding wheel electrode  46  may be adjustably biased against wire  22  to adjust the weld force applied by the welding wheel electrode  46  to wire  22 . 
     Welding support assembly  40  includes a vertical mounting frame  48  attached to a shelf  52 . Cylinders  50 , which in one aspect may be hydraulic and/or pneumatic, are attached to shelf  52  at mounting brackets  56 . Cylinders  50  are placed on opposing sides of frame  48 . A cylinder rod  58  extends from each cylinder  50  through shelf  52  to mounting bracket  60  of mounting structure  42 . Cylinder rods  58  are attached to bracket  60 . Cylinders  50  are each vertically oriented. Cylinders  50 , cylinder rods  58 , shelf  52 , and bracket  60  are arranged to allow for controlled vertical movement of shelf  52 , and accordingly, for controlled vertical movement of support assembly  40  in relation to mounting structure  42 . 
     A motor  70  is provided on bracket  60  such that the motor shaft  72  extends vertically through bracket  60 . A coupler  74  is mounted below bracket  60  and connects motor shaft  72  to lead screw  64 . Lead screw  64  is a helically-threaded shaft of a ball screw type linear actuator system (comprising motor  70 , shaft  72 , coupler  74 , and screw  64 ). A ball nut (not shown) is attached to support assembly  40 . Motor  70 , lead screw  64 , and the ball nut cooperatively allow controlled vertical movement of support assembly  40  in relation to mounting structure  42  by operation of motor  70 . Motor  70  is electronically connected to processor  9  of control panel  8  to allow controlled operation of motor  70  and thereby controlled vertical movement of support assembly  40  and of welding wheel electrode  46 . 
     Referring to  FIG. 3 , a side view of a guide channel  94  and a guide bracket  96  is shown. Two guide channels  94  are fixedly attached to mounting structure  42 . Each guide channel  94  is vertically oriented. Guide brackets  96  are attached to support assembly  40 . Guide brackets  96  and guide channels  94  are sized and structured to allow vertical movement of support assembly  40  in relation mounting structure  42 , but to limit horizontal movement of support assembly  40  in relation to mounting structure  42 . 
     A force measurement device (such as a load cell)  100  is provided in the welding assembly  10  to determine forces, and therefore pressure applied by the welding wheel electrode  46  to the wire  22  during a welding process. The load cell  100  is positioned intermediate mounting structure  42  structure contact plate  57  and support assembly  40  support contact plate  59 . Load cell  100  may comprise a commercially available precision compression loading type load cell. Specifically, load cell  100  measures forces applied to load cell  100  by structure contact plate  57  and support contact plate  59 . 
     In an exemplary embodiment, load cell  100  is electronically connected to processor  9  of control panel  8  to provide continuous or intermittent communication of measured forces. Accordingly, motor  70  may be operated as a closed loop process wherein load cell  100  measured forces are processed. Processor  9  control commands responsive to measured forces are provided pursuant to predetermined parameters to motor  70 , thereby inducing operation of motor  70  to move support assembly  40  in relation to mounting structure  42  to increase or decrease applied force. 
     Welding wheel electrode  46  is supported in a fixed vertical orientation on support assembly  40  during a welding process. Spindle  14 , on which head  66  is positioned, is in a fixed vertical position in relation to mounting structure  42 . Accordingly, head  66 , together with ribs  20  and wire  22  supported thereon, is positioned in a fixed vertical position in relation to mounting structure  42 . Accordingly, for any given welding process, welding wheel electrode  46  may be positioned on the faying surfaces of ribs  20  and wire  22 . Upon calibration, the applied pressure of welding wheel electrode  46  to faying surfaces of ribs  20  and wire  22  may be determined. Applied pressure may then be adjusted by relative movement of support assembly  40  in relation to mounting structure  42 . 
     Cylinders  50  dampen the movement of support assembly  40  in relation to mounting structure  42 , thereby allowing controlled pressure application with self-correcting, dampening adjustments for variations, such as variations resulting from rotation eccentricities of the welding wheel electrode and spindle, welding wheel contact surface wear, and depth variations of faying surfaces. 
     Referring to  FIG. 1 , the weld pressure assembly  10  of the present invention includes a processor  9  in control module  8 . Load readings from load cell  100  are transmitted to processor  9 . Processor  9  is programmable to operate motor  70  and accordingly adjust position of support assembly  40  according to given conditions. Processor  9  is operable, continually or intermittently, to receive load data from load cell  100  and to adjust the vertical position of motor  70  to achieve a desired pressure level of welding wheel electrode  46  on wire  22 . Such force level is indicated by load cell  100 . 
     Operation 
     In operation, ribs  20  are extended through openings  26 , and wire  22  is positioned on a rib  20 . Each rib  20  and wire  22  comprise faying surfaces for welding by welding wheel electrode  46 . 
     At the beginning of a welding process, welding wheel electrode  46  is positioned on wire  22 . The indicated forces applied to load cell  100  are determined. Servo motor  70  is operated to provide a load of support assembly  40  in relation to structure  42 , thereby providing a determined pressure of welding wheel electrode  46  on faying surfaces of wire  22  and ribs  20 . As welding wheel electrode  46  is fixedly attached to support assembly  40 , and wire  22  and rib  20  faying surfaces supported on spindle  14  are in a vertically fixed orientation in relation to mounting structure  42 , the pressure applied by welding wheel electrode  46  to wire  22  and rib  20  is also determined. 
     Pressure applied within cylinders  50  is electronically controlled to maintain a determined cylinder pressure to offset the weight load of support assembly  40 . As cylinder rods  58  are mounted on mounting structure  42 , cylinders  50  can be adjusted to provide a determined load on load cell  100  as load cell  100  measures load applied intermediate contact plate  57  of mounting structure  42  and contact plate  59  of support assembly  40 . Accordingly, by application of appropriate force by cylinders  50 , the indicated load at load cell  100  between contact plates  57  and  59  can be set to zero (or other determined force). 
     With the determined initial position, processor  9  is operated to control motor  70  to operate lead screw  64  to vertically bias support assembly  40  in relation to mounting structure  42  until a determined application load force is obtained. The observed indicated load of load cell  100  indicates the pressure applied by welding wheel electrode  46  to the faying surfaces of wire  22  and ribs  20 . 
     As spindle  14  of headstock  12  is rotated and welding wheel electrode  46  powered, the wire  22  is welded to successively rotated ribs  20 . Rotation of spindle  14  results in wire  22  being drawn from spool  32  during welding operation. Processor  9  of control panel  8  is operated during a welding process to rotate spindles  14  and  30  concurrently and at like rotation speeds, to control lateral movement of tailstock  16 , and to control pressure applied by welding pressure assembly  10  during the welding process. 
     Referring to  FIG. 4 , an exemplary method  200  of the present invention is disclosed for providing controlled welding pressure in a wire wrap screen manufacturing process, the method comprising the steps indicated herein. 
     A rib support step  202  comprises providing a support for ribs  20 , said support comprising a rotating head  66 . 
     A wire feed step  204  comprises providing wire  22  to an intersecting surface of a rib  20 . 
     A welding device placement step  206  comprises providing a welding wheel electrode  46  supported on a support assembly  40  in contact with a wire  22  supported on a rib  20 . 
     An initial force determination step  208  comprises determining pressure exerted on wire  22  by welding wheel electrode  46 . Such determination is made by load cell  100  and indicates the load of support assembly  40  in relation to mounting structure  42 . Such force is measured intermediate contact plate  57  and contact plate  59 . Support assembly  40  is supported by a mounting structure  42 . 
     A pressure adjustment step  210  comprises adjusting pressure of the welding wheel electrode  46  on wire  22  to a predetermined level. Pressure adjustment step  210  is accomplished by adjusting pressure within cylinders  50 . Pressure adjustment may be further accomplished by servo motor  70  as part of a linear actuator system. 
     A welding step  212  comprises welding wire  22  to the rib  20  at the intersection of wire  22  and the rib  20 . 
     A rotating step  214  comprises rotating spindle  14 . 
     A linear drive step  216  comprises driving tailstock  16  along axis A-A away from headstock  12 . 
     A feedback step  218  comprises continuous or intermittent measurement of indicated load intermediate contact plate  57  and contact plate  59 . 
     A control step  220  comprises continuous or intermittent receipt of indicated load data, processing received data, and output of control commands according to predetermined parameters. 
     An adjustment step  222  comprises operation of the linear actuator system by servo motor  70  to move support assembly  40  in relation to mounting structure  42 , thereby increasing or decreasing, as determined by operation parameters, pressure applied by welding wheel electrode  46  to wire  22  and ribs  20 . 
     In an embodiment of the present invention, feedback step  218  involves measuring various data in relation to the system; including rotation speed of spindle  14 , rotation speed of spindle  30 , and linear travel of tailstock  16 . In such embodiment, control step  220  includes receipt of indicated load data related to spindle  14  rotation speed, spindle  30  rotation speed, and linear travel of tailstock  16 ; processing the data; and output of control commands according to predetermined parameters. In such embodiment, adjustment step  222  comprises adjustment of spindle  14  rotation speed, spindle  30  rotation speed, and linear travel of tailstock  16 . 
     While the preferred embodiments of the invention have been described and illustrated, modifications thereof can be made by one skilled in the art without departing from the teachings of the invention. Descriptions of embodiments are exemplary and not limiting. The extent and scope of the invention is set forth in the appended claims and is intended to extend to equivalents thereof. The claims are incorporated into the specification. Disclosure of existing patents, publications and known art are incorporated herein to the extent required to provide reference details and understanding of the disclosure herein set forth.