Patent Publication Number: US-2005115293-A1

Title: Thread rolling tool

Description:
BACKGROUND OF INVENTION  
      1. Field of the Invention  
      The present invention is generally related to the field of thread formation, and, more particularly, to a thread rolling tool that may be employed in forming threads on various components.  
      2. Description of the Related Art  
      Threaded connections are very commonplace for connecting various components to one another. For example, in the oilfield industry, sections of pipe or tubulars are sometimes connected to one another by a threaded connection, i.e., a box (female) threaded connection formed on one end of a pipe, and a pin (male) threaded connection formed on the other end of the pipe. Sections of pipe are coupled to one another by these threaded connections. Of course, there are many other industries and applications where threaded connections are routinely and widely employed.  
      There are a variety of well known manufacturing techniques for forming threads on the various components. Moreover, the size, shape and configuration of the threads formed by such processes may vary widely depending upon the particular application and the anticipated loading conditions. In some cases, threads are formed by a process wherein a cutting tool is employed to form the threads in the component, e.g., a section of pipe, using a lathe and known tooling components. Thereafter, in some cases, it is desirable that the mechanical properties of the threads be enhanced by cold working the threads, i.e., it is desirable to enhance the mechanism properties of the root of the threads and the various thread surfaces where high stress points could result in fatigue failure. By cold working the threads, various mechanical properties of the thread may be improved, e.g., hardness, etc. There are many tools and techniques on the market for cold working threads. Most of such thread rolling tools are designed to fit onto CNC machines and/or are designed for use with industry standard thread profiles, e.g., API connectors.  
       FIG. 1  provides a schematic example of at least one technique for cold working threads formed on a component. As depicted therein, a plurality of schematically depicted threads  10  are formed on a component  12 . A cold roll wheel  14  having an end  16  is depicted positioned above the threads  10 . After the threads  10  are initially formed by, for example, a cutting process, the cold roll wheel  14  may be used to cold work the threads  10 . Ideally, the end  16  of the wheel  14  will be positioned in the threads  10  such that the end  16  is aligned with the root  18  of a particular thread. Thereafter, force is applied to the cold roll wheel  14  (by, for example, actuating one or more levers on the lathe) and the wheel  14  follows the path of the threads  10  thereby cold working the threads  10  to improve the mechanical properties thereof.  
      However, in practice, it is very difficult to precisely locate the end  16  of the cold roll wheel  14  at the desired location on the thread profile. More specifically, in most thread rolling tools, the relative position of the end  16  of the cold roll wheel  14  relative to a holder (not shown) that is used to secure the cold roll tool to a machine tool is fixed. Thus, in using the existing thread rolling tools, a machinist must expend great time and effort trying to insure that the end  16  of the wheel  14  is properly positioned in the root  18  of the thread  10 . Such efforts may include the use of mirrors and additional lighting in an effort to insure that the end  16  is properly located in the root  18 . Properly locating the end  16  in the root  18  of the thread is critical to the cold working operation. Absent proper alignment, the cold working process, where pressure on the order of, for example, approximately 1000 psi or so is applied to the thread  10  via the wheel  14 , may damage or destroy the previously formed thread profiles. For example, a wheel  14  (in dashed lines) that is misaligned with respect to the root  18  is depicted in  FIG. 1 . If the end  16  of the misaligned wheel  14  is located at a position relatively far from the root  18  of the thread, application of pressure to the wheel  14  to cold work the threads may damage the existing thread profile. At a minimum, the cold working process may not result in the desired finished product if the end  16  of the wheel  14  is not properly positioned in the threads  10 . Moreover, the positioning of prior art thread rolling tools is very time consuming, thereby limiting productivity. Lastly, due to the difficult in properly aligning the prior art thread rolling tool described above, the chance of producing defective end products is increased.  
      The present invention is directed to an apparatus and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.  
     SUMMARY OF INVENTION  
      The present invention is directed to a thread rolling tool that may be used in forming various threads. In one illustrative embodiment, the tool comprises a tool holder, a boring bar and a cold roll wheel operatively coupled to the boring bar, wherein a position of the cold roll wheel relative to the tool holder along a first direction is moveable.  
      In another illustrative embodiment, the tool comprises a tool holder, a boring bar slidingly coupled to the tool holder to thereby allow movement of the boring bar in a first direction relative to the tool holder, and a cold roll wheel operatively coupled to the boring bar.  
      In yet another illustrative embodiment, the tool comprises a tool holder, a boring bar that extends through and is slidingly coupled to the tool holder to thereby allow movement of the boring bar in a first direction relative to the tool holder, a cold roll wheel operatively coupled to the boring bar and at least one projection for limiting travel of the boring bar relative to the tool holder along the first direction.  
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements.  
       FIG. 1  is a schematic depiction of an illustrative thread profile in a cold forming tool in accordance with prior art techniques.  
       FIG. 2  is a schematic depiction of an illustrative lathe having a thread rolling tool in accordance with one aspect of the present invention positioned therein.  
       FIGS. 3A-3C  are various views of an illustrative thread rolling tool in accordance with one embodiment of the present invention.  
       FIGS. 4A and 4B  are views of one illustrative embodiment of the thread rolling tool during the assembly process.  
       FIGS. 5A and 5B  are illustrative views of a thread rolling tool in accordance with the present invention positioned in a lathe. 
    
    
      While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
     DETAILED DESCRIPTION  
      Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.  
      The present invention will now be described with reference to the attached figures. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.  
      In general, the present invention is directed to a thread rolling tool that may be used in cold working threads. As will be recognized by those skilled in the art after a complete reading of the present application, the present invention may be employed with the formation of a variety of different types of threads on a variety of different type components. Thus, the present invention should not be considered as limited to the formation of any particular type of thread on any particular type of component unless such limitations are expressly set forth in the appended claims.  
       FIG. 2  is a schematic depiction of an illustrative lathe  20  having a thread rolling tool  22  in accordance with one embodiment of the present invention positioned therein. The lathe  20  is provided by way of example only and it should be understood to be representative of any of a variety of different types of lathes or other machinery used to initially form a thread prior to performing a cold working process on the thread, or a machine that is involved in any process of cold working threads. Thus, the present invention should not be considered as limited in any respect as to the equipment or methodologies used in forming the thread unless such limitations are expressly set forth in the appended claims. As shown therein, the lathe  20  is comprised of a head stock  24 , a chuck  26 , a tool post  30 , a bed  32 , a cross slide lever  34 , a longitudinal slide control  36  and a gear engagement lever  38 . Also depicted in  FIG. 2  is an illustrative workpiece  28 , e.g., a section of pipe. The thread rolling tool  22  is secured to the tool post  30  by a plurality of threaded pins  31 .  
       FIGS. 3A and 3C  are top and side views, respectively, of one illustrative embodiment of the thread rolling tool  22  disclosed herein.  FIG. 3B  is an enlarged view of a portion of the thread rolling tool  22 . As shown in these drawings, the thread rolling tool  22  is comprised of a moveable boring bar  42  that is slidingly coupled to a tool holder  40 . That is, there is a sliding clearance between the tool holder  40  and the moveable boring bar  42  to allow the bar  42  to slide within the tool holder  40  in a first direction, as indicated by the double arrow  60 , i.e., in a direction that is approximately parallel to the longitudinal axis of the boring bar  42 . In the depicted embodiment, the tool holder  40  is comprised of a generally cylindrical body  41  and a clamp block  46  that is of a generally rectangular shape. A key  44  is used to limit relative movement between the moveable boring bar  42  and the tool holder  40  in a second direction, i.e., to limit rotational movement between the moveable boring bar  42  and the tool holder  40  around the longitudinal axis of the boring bar  42 . Also, projections  48 , i.e., screws, are provided to limit relative longitudinal movement of the moveable boring bar  42  relative to the tool holder  40  in the first direction. In one illustrative embodiment, the screws  48  are located in position so as to limit the relative travel between the moveable boring bar  42  and the tool holder  40  along the first direction  60  to approximately 1-2 inches. Of course, the limit of this travel may be adjusted depending upon a particular application. In the depicted embodiment, the clamp block  46  has a generally rectangular configuration to facilitate securement of the thread rolling tool  22  to the tool post  30  on the lathe  20  via the threaded pins  31 . Of course, as will be recognized by those skilled in the art, this particular configuration may be varied depending upon, for example, the configuration of the machine that employs the thread rolling tool  22  of the present inventions. That is, other mechanisms may be provided to insure that the thread rolling tool  22  may be secured to a machine, e.g., lathe  20 , that may be employed in using the present invention.  
      The thread rolling tool  22  further comprises a cold roll wheel  50  having an end  51 , a piston  52 , a dowel pin  54  that connects the wheel  50  to the piston  52 , a piston limit pin  56  that is used to limit the vertical movement of the piston  52  and an O-ring  58  that provides the necessary seal for hydraulic fluid employed in the present invention. The moveable boring bar  42  has an internal passageway  62  formed therein and a pressure gauge  63  is coupled to the moveable boring bar  42 . The hydraulic fluid within the internal passageway  62  transmits the pressure acting on the wheel  50  to the pressure gauge  63 . This pressure may be observed by a machinist.  
       FIGS. 4A and 4B  are various views depicting the assembly sequence of the thread rolling tool  22  in accordance with one embodiment of the present invention. As shown in  FIG. 4A , a slot  66  is formed in the moveable boring bar  42  and a key  44  is positioned therein. The size and configuration of the key  44  and slot  66  may vary depending upon the desired application. In one illustrative embodiment, the key  44  may be approximately four inches in length (along the axial direction of the moveable boring bar  42 ) and its surface  44 A may protrude above a surface  42 A of the moveable boring bar  42  by a distance of approximately one-half inch. A slot  68  is formed in the tool holder  40  and is adapted to receive the key  44  positioned therein. The use of the key  44  limits relative movement of the moveable boring bar  42  and the tool holder  40  in a given direction, i.e., the key  44  limits relative rotational movement between the tool holder  40  and the moveable boring bar  42 . As indicated in  FIG. 4B , after the tool holder  40  is properly positioned over the key  44 , protrusions, i.e., screws  48 , may be secured in place at the desired location to thereby limit the relative travel between the moveable boring bar  42  and the tool holder  40  in a first direction, e.g., in a longitudinal direction that is approximately parallel with a longitudinal axis of the moveable boring bar  42 .  
      The operation and use of the thread rolling tool  22  of the present invention will now be described. At some point during the course of assembly of the thread rolling tool  22 , hydraulic fluid will be introduced into the internal passageways  62  of the tool, via openings provided for the protrusions  48 , e.g., screws, and/or the opening provided to allow fluid communication with the pressure gauge  63 . Typically, the screws  48  will be used as a means to fill and bleed off air within the internal passageway  62  and/or the piston  52  of the thread rolling tool  22 . Once the system is properly filled with hydraulic fluid, it may be positioned on the tool post  30  as indicated in  FIGS. 5A and 5B . As shown therein, the thread rolling tool  22  is secured within the tool post  30  of the lathe  20  via a plurality of threaded pins  31 . The threaded pins  31  engage the clamp block  46  on the tool holder  40 . Of course, as indicated before, the particular mechanism and manner by which the tool holder  40  is secured to the lathe  20 , or any other type of machinery, may vary depending upon the particular application.  
      Once the thread rolling tool  22  of the present invention is properly positioned in the lathe  20 , the machinist then advances the end  51  of the cold roll wheel  50  to a point where it is proximate a previously formed thread profile. By incremental actuation of various control levers on the lathe  20  and/or movement of the moveable boring bar  42 , the end  51  of the cold roll wheel  50  may be brought into engagement with previously formed threads on the workpiece  28 . Due to the fact that the thread rolling tool  22  of the present invention allows relative movement, e.g., in a longitudinal direction, between the cold roll wheel  50  and the tool holder  40 , the end  51  of the wheel  50  can move (in a lateral direction) so that it may tend to naturally find the proper position within the thread profile, i.e., the end  51  may be positioned at the root of the thread prior to beginning cold working operations. Moreover, as the lathe is actuated to apply pressure to the end  51  of the wheel  50 , the self-alignment forces tend to become greater, i.e., the end  51  would tend to be biased toward the root of a particular thread profile due to the various tapered surfaces.  
      Through use of the present invention, the end  51  of the cold roll wheel  50  may be more quickly and properly positioned at the desired location prior to beginning cold working operations. Due to the allowed relative longitudinal movement between the cold roll wheel  50  and the tool holder  40 , the present invention enables a machinist to readily locate and position the end  51  of the cold roll wheel  50  at the desired location. In turn, this improves manufacturing inefficiencies and leads to reduced waste.  
      The present invention is directed to a thread rolling tool that may be used in forming various threads. In one illustrative embodiment, the tool comprises a tool holder, a boring bar and a cold roll wheel operatively coupled to the boring bar, wherein a position of the cold roll wheel relative to the tool holder along a first direction is moveable.  
      In another illustrative embodiment, the tool comprises a tool holder, a boring bar slidingly coupled to the tool holder to thereby allow movement of the boring bar in a first direction relative to the tool holder, and a cold roll wheel operatively coupled to the boring bar.  
      In yet another illustrative embodiment, the tool comprises a tool holder, a boring bar that extends through and is slidingly coupled to the tool holder to thereby allow movement of the boring bar in a first direction relative to the tool holder, a cold roll wheel operatively coupled to the boring bar and at least one projection for limiting travel of the boring bar relative to the tool holder along the first direction.  
      The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.