Abstract:
A latch device for a manual tong apparatus that incorporates a secondary catch mechanism is presented. Such a secondary catch would assist in maintaining the tong assembly in it&#39;s closed position during a reversing operation or at a time when load applied to the manual tong device in the gripping direction is very low. Additionally the secondary catch would also provide some additional protection by holding the tong assembly together in the event of a failure of certain tong components. The mechanism of the secondary catch is spring loaded and operates through two secondary up-down catch arms that are deactivated by swinging a handle in the direction that corresponds to the operator&#39;s natural motion to open the lug jaw.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
         [0001]    None.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention generally relates to the use of latches to hold jointed sections of manual pipe tongs as deployed in the oilfield industry together. More particularly, the invention relates to the addition of a secondary safety latch to a set of manual pipe tongs to prevent the undesired opening of the tong jaws.  
           [0004]    2. Description of the Related Art  
           [0005]    Manual pipe tongs are used throughout the oilfield industry to transmit torque to various tubular components of generally cylindrical shape. This assisted transmission of torque is most often used to secure, tighten (make-up), and loosen (break-out) the threaded connections of drill pipe, drill collars, casing, and tubing. Pipe tongs typically function by incorporating a cantilevered configuration that holds the workpiece in a grip that tightens as more torque is applied to the lever arm.  
           [0006]    [0006]FIG. 1 shows a typical prior art manual tong assembly  10  as used in oilfield drilling operations to secure or rotate a generally cylindrical workpiece  12 . This particular example of a manual tong assembly  10  includes a long jaw  14 , a short jaw  16 , a lug jaw  18 , and a lever arm  20  all connected together at pivot points  22 . A latch  24  is pinned to one end of the long jaw  14  and fits into a receiver step  26  at the end of the lug jaw  18 .  
           [0007]    [0007]FIGS. 2 a  and  2   b  show how different workpiece  12  sizes can be accommodated by adjusting the lengths and configurations of lug jaw  18 . FIG. 2 a  shows a lug jaw  18  that includes an array of mounting locations  28  and a choice of receiver steps,  26  and  30 , that may be used to adjust to various workpiece diameters (e.g. pipe diameters). Similarly, FIG. 2 b  details a hinged lug jaw  32  that is greater in length than lug jaw  18  and includes a hinged portion  34  attached to a lug portion  36  by means of a hinge  38  to allow even larger diameter workpieces to be accommodated by tong assembly  10 .  
           [0008]    Referring again to FIG. 1, jaws,  14 ,  16 , and  18  are positioned around workpiece  12  and locked into place with latch  24 . Each jaw may contain one or more sets of sharpened teeth  40  (tong dies) that are used to “bite” into workpiece  12  and prevent slippage when manual tong  10  is engaged. Once latch  24  is engaged, lever arm  20  can be rotated in direction α so that latch  24  is loaded in tension and tool  10  engages and applies torque to workpiece  12  in the α direction. Rotating lever arm  20  in direction ω will loosen jaw&#39;s  14 ,  16 , and  18  and allow latch  24  to be released. Several handles such as  42  and  44 , are typically placed about the periphery of manual tong assembly  10  to provide locations for rig workers to guide tong assembly 10  during operations.  
           [0009]    Manual tong  10 , as illustrated, is configured to only grip workpiece  12  when torque is applied on the α direction. Typical rig operations incorporate two sets of manual tongs, with each one being the mirror image of the other, so that one tightens in clockwise direction and the other in a counter-clockwise direction. Each can tighten or loosen the pipe threads, depending on whether it is installed in the upper position for rotating the pin (male) connection or the lower position for holding the box (female) connection. The number of tongs used in an operation and their position on the workpiece relative to each other depends on the operation being performed and the type of additional rig equipment used.  
           [0010]    It has been found that conventional tongs sometimes allow the undesired release of latch  24  when the tong is rotated in direction ω. After workpiece  12  has been positioned, it sometimes becomes necessary to slidably rotate manual tong  10  backwards (counter-clockwise as drawn, in the co direction) about workpiece  12 , in a manner similar to a ratchet, so that the engagement and rotation steps can be repeated. Latch  24  of FIG. 1 is designed to engage when the manual tong device is loaded in direction α. If the load applied in direction α were slackened, or if the tong is rotated in direction ω, the latch device can release undesirably, allowing tong jaws  14 ,  16 , and  18  to rotate and swing free of workpiece  12 . Because jaws,  14 ,  16  and  18  are typically quite massive, such undesired openings can be hazardous, as well as requiring that operations cease until they are repositioned and secured. Any improvement made in latch  24  of manual tong  10  that is able to reduce such undesired openings would increase safety and reduce down-time and the costs associated therewith.  
           [0011]    In addition, manual tong components occasionally work themselves loose during operations, which can cause the tong apparatus to open unexpectedly and rapidly. This undesired failure has great potential to cause physical harm to operators and nearby support personnel. This potential for injury can be greatly magnified if the tong is being operated under high loads at the time of the undesired opening. For this reason, a system that maintains the jaws in a closed configuration in the event of such a failure is highly desirable.  
         BRIEF SUMMARY OF THE INVENTION  
         [0012]    According to the present invention, the issues noted above are addressed by providing a latch device for a manual tong that incorporates a secondary catch mechanism. Such a secondary catch assists in maintaining the tong assembly in its closed position during a reversing operation or at a time when load applied to the manual tong device in the gripping direction is very low. Additionally the secondary catch provides protection from undesired release by holding some components of the tong assembly together in the event of a failure of certain tong components. The mechanism of the secondary catch is spring loaded and is deactivated by swinging a handle in a direction that corresponds to the operator&#39;s natural motion to open the lug jaw. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    For a detailed description of a preferred embodiment of the invention, reference will now be made to the accompanying drawings wherein:  
         [0014]    [0014]FIG. 1 is a top view of a prior art manual tong apparatus;  
         [0015]    [0015]FIG. 2 a  is a detail drawing of a lug jaw of the manual tong apparatus of FIG. 1;  
         [0016]    [0016]FIG. 2 b  is an alternative to the lug jaw of FIG. 2 a;    
         [0017]    [0017]FIG. 3 is a perspective view of a latch assembly in the closed position in accordance with a preferred embodiment of the present invention;  
         [0018]    [0018]FIG. 4 is a perspective view of the latch assembly of FIG. 3 in the open position;  
         [0019]    [0019]FIG. 5 is a perspective view of the lug jaw of FIG. 3;  
         [0020]    [0020]FIG. 6 is an enlarged view of the latch arm of FIG. 3;  
         [0021]    [0021]FIG. 7 is a perspective view of the up-down rocker arm of FIG. 3;  
         [0022]    [0022]FIG. 8 is a perspective view of a torsion spring in accordance with a preferred embodiment of the present invention; and  
         [0023]    [0023]FIG. 9 is a top view drawing of a 
     
    
       [0024]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    Referring initially to FIG. 3, a close up of a preferred embodiment for a latch lock system  100  of a manual pipe tong apparatus is shown. Preferred latch lock system  100  includes a modified lug jaw  102 , a latch arm  104  mounted to long jaw  105 , a handle  106 , and a secondary catch system  108 . Secondary catch system  108  further includes a pivot member  110 , two rocker arms  112 , and a latch (catch) receiver  114  integral with lug jaw  102 . Rocker arms  112  are attached to latch arm  104  by fasteners  128 .  
         [0026]    Pivot member  110  includes an engagement member  116 , is secured to the end of latch arm  104  by fastener  120  and is free to rotate in directions σ and τ about a handle axis  121 . Handle  106  can be of any design or configuration available but is preferably a bolt on device that is removably secured at location  122  at the end of pivot member  110 . Such a handle is described in U.S. patent application Ser. No. 09/505074 filed on Feb. 16, 2000 entitled Multi-Piece Manual Tong Safety Handle hereby incorporated herein by reference.  
         [0027]    Fasteners  128  and  120  can be of any permanent, semi-permanent, or temporary type of fastener but are preferably generally cylindrical in form and include a longitudinal axis. Although fasteners  128  and  120  shown in FIG. 3 are shown as threaded bolts with corresponding nuts, screws, clevis pins, or press-fit rods may be used in their place without changing the function of the device presented herein. Torsion springs  130  (not visible in FIG. 3 but shown in FIG. 8) are mounted on fasteners  128  so as to bias rocker arms  112  toward lug jaw  102 .  
         [0028]    Referring now to FIG. 5, a preferred embodiment of lug jaw  102  includes latch receiver  114 , a handle  150 , latch steps  152  and  154 , and a location  156  to mount tong die teeth. Handle  150  is to assist in the manipulation of tong apparatus and is shown as a simple cast-in bar handle but can be of any configuration preferable to the tong operator or manufacturer. Latch receivers  114  are provided as integral bosses on each of the top and bottom faces  158 , 160  of lug jaw  102  in the latching region. Latch receivers  114  can either be cast or forged into place upon lug jaw  102  during manufacture or can be secured to lug jaw  102  using any standard attachment method following manufacture of lug jaw  102 . Latch receiver  114  attachment methods can include but are not limited to welds, brazed joints, bolts, rivets, adhesives, or interference fits. Latch receivers  114  preferably have a tapered leading edge  162  and a trailing edge  164  that is generally perpendicular to the face ( 158  or  160 ) to which latch receiver  114  is mounted. Latch steps  152  and  154  are for receiving latch arm  104  as shown in FIGS. 3 and 4 in position on manual tong device and correspond to the various gauge sizes that lug jaw  102  is able to accommodate.  
         [0029]    Referring now to FIG. 6, latch arm  104  is shown in more detail. Latch arm  104  includes an attachment end  170  and a latch end  172 . Attachment end  170  includes a bore  174  for attaching latch arm  104  to the end of long jaw  105  of FIG. 3. Each end of bore  174  forms an annular wear face  176 . Latch end  172  includes an upset portion  178 , bores  180 , and rocker arm mounts  182  and  184  on surface  186 . Upset portion  178  is fashioned so that it seats securely within the corresponding geometries of latch steps  152 ,  154  of lug jaw  102  (FIG. 5). Bores  180  allow the mounting of pivot member ( 110  of FIG. 3) to latch arm  104 . Rocker arm mounts  182  and  184  are positioned in line with locations  124  and  126  of FIG. 3 to retain rocker arm device  112  and fasteners  128  in place. A gap exists between rocker arm mounts  182  and  184  to allow for torsion spring  130  of FIG. 8 to be easily positioned. One set of rocker arm mounts  182  and  184  is used for each rocker arm utilized in latch lock system  100 .  
         [0030]    Referring now to FIG. 7, a preferred rocker arm  112 , as used in secondary catch system  108  of FIG. 3, includes a back  200  and a top  202  positioned approximately 90° relative to each other. Mounting holes  204  are preferably positioned in a coaxial arrangement that defines an axis  205  that is generally parallel to the intersection between back  200  and top  202 . Holes  204  are positioned and sized so that rocker arm  112  can be mounted upon mounts  182  and  184  by fasteners  128 . Once mounted, rocker arm is allowed to pivot about axis defined by holes  204 . At a remote end of top  202  is a catch  206  that generally corresponds to the profile of latch receivers  114 .  
         [0031]    [0031]FIG. 8 details a perspective view of a preferred torsion wire spring  130  for use in latch lock mechanism  100 . Torsion wire spring  130  includes tines  210  and  212 , and a coil  214  that defines a center axis  216 . Squeezing tines  210  and  212  together, activates coil  214  and results in spring forces that urge tines  210  and  212  apart. Torsion springs  130  are preferably mounted on fasteners  128  of FIG. 3 to bias rocker arms  112  toward lug jaw  102 . An additional torsion spring (not shown) may also be mounted upon the axis of fastener  120  in order to bias handle  106  and pivot member  110  in direction σ but is not required. Torsion springs  130  and  132  may be manufactured from identical components in order to keep production costs at a minimum.  
         [0032]    Referring to FIGS. 3 and 6- 8 , the installation of the two rocker arms upon latch arm  104  can be described. Torsion wire springs  130  are placed in between rocker arm mounts  182  and  184  of and held tightly in place while fasteners  128  are passed through holes  204 , mounts  182  and  184 , and coils  216 . For each spring  130  installed, one tine engages back  200  of rocker arm  112  while the other tine  212  engages surface  186  adjacent to upset portion  178  of latch arm  104  FIG. 6. Once installed, rocker arms  112  are allowed to pivot around fasteners  128  in an up-down fashion, with torsion spring  130  biasing top  202  of each rocker arm toward upset portion  178  of latch arm  104 . Following installation of rocker arms  112 , pivot member  110  and handle  106  can then be added to latch arm at location  180  by fastener  120 . Once handle and pivot member are installed, latch lock system  100  is operable.  
         [0033]    Latch lock system  100  of FIG. 3 is engaged by swinging long jaw  105  and latch arm  104  into position with lug jaw  102  of FIG. 5 so upset portion  178  of latch arm engages latch step  152  or  154 . With typical prior art latches, this mechanism is all that holds lug jaw  102  and long jaw  105  together, making the connection dependant on tension between jaws  102  and  105  to maintain latch arm  104  within latch step  152  or  154 .  
         [0034]    When this connection is made with the latch lock system  100  of the present invention, the tapered profiles  162  of latch receivers  114  deflect catch points  206  of rocker arms  112  away from lug jaw  102 , allowing them to slide over latch receiver  114 . Once catch point  206  of each rocker arm has cleared latch receiver  112 , torsion spring  130  forces rocker back against lug jaw  102 , allowing the profile of catch point  206  to engage perpendicular edge  164  of receiver  114 . This action provides a secondary connection to prevent separation of jaws  102  and  105  if tension is lost between them or if tong apparatus is rotated backwards.  
         [0035]    Referring now to FIG. 4, the disengagement of latch lock system  100  can be described. When desired, latch lock system  100  may be disengaged by first deactivating secondary catch system  108 , then removing latch arm,  104  from lug jaw  102 . To deactivate secondary catch system  108 , pivot member  110  with attached handle  106  is rotated about axis  121  in the τ direction. Rotating pivot member  110  enables engagement member  116  to strike the back faces  200  of rocker arms  112  causing them to oppose torsion springs  130  and pivot about fasteners  128 . In the pivoted position, catch tips  206  of rocker arms  112  are cleared from latch receivers  114  upon lug jaw  102 , thus enabling latch arm  104  to be swung free from lug jaw  102 . Once handle  106  and pivot member  110  have been swung in direction τ, latch lock system  100  is able to function in a manner similar to a conventional manual tong latch.  
         [0036]    Referring now to FIG. 9, a top view of the engagement member  116  of pivot member  110  is shown. Engagement member  116  shown includes a cutout notch  117  to grasp back  200  of rocker arm  112  when latch lock system is engaged. Notch  117  acts as a hook to retain the rear of rocker arms  112  in the event of a component failure and acts as an additional safety measure. With notch  117  securely around rocker arms  112 , latch lock system  110  cannot be opened unless pivot member  110  is rotated in direction T (as shown in FIGS.  3 - 4 ). As mentioned above, a torsion spring (not shown) may be employed about fastener ( 120  of FIGS.  3 - 4 ) at location  121  to bias pivot member  110  in direction σ to prevent premature release in the event of a failure. To disengage latch lock system  100 , pivot member  110  is rotated in direction τ and rocker arms  112  are released by notch  117  and engaged by the remainder of member  116 . With rocker arms  112  engaged, secondary catch  108  is deactivated, allowing latch lock system  100  to be opened.  
         [0037]    Latch lock system  100  is desirable over designs of the prior art because it provides added measures of safety and convenience to the operators of manual pipe tongs in rig environments. For sake of convenience, the latch lock device maintains the jaws of manual tong apparatus closed when a state of tension does not exist within the latch arm. Without latch lock mechanism  100 , jaws of manual tong could open if the load applied to tong were slackened or if tong were rotated counter to the gripping direction, in a matter similar to a ratchet. The operator of a manual tong apparatus incorporating latch lock assembly  100  is granted and additional level of safety in the event of a failure of a manual tong component. Without safety latch lock, the latch arm of a manual tong apparatus can release from the lug jaw rapidly and strike a nearby rig operator.