Abstract:
A locking system for a connection between two parts, comprising a first part; a second part for connection with the first part; and an interfering member, the member constructed and arranged to permit connection and thereafter, to prevent separation of the parts.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention generally relate to a connection system for a threaded connection. More particularly, the invention relates to a locking system for a threaded connection between two parts of a downhole apparatus. 
         [0003]    2. Description of the Related Art 
         [0004]    Threaded connections are used routinely to join two pieces of equipment together for use in a wellbore. In one example, a nose piece is fitted to a body or mandrel of a tool to facilitate the insertion of the tool into a wellbore. The connection is intended to be “permanent” with no need to separate the two pieces. In fact, separation of the pieces is to be avoided as the tool can malfunction or otherwise become inoperable due to separation of components in operation. Presently, various methods are used to prevent parts from becoming unthreaded in use. In one example, an aperture is drilled through the connection and a pin is inserted. Thereafter, the pin head is deformed to prevent the pin from backing out. In another example the threads are “locked” with cement. In yet another arrangement the threads are welded. These arrangements are time-consuming, unreliable and not uniform in their use. 
         [0005]    What is needed is a more effective way of keeping threaded parts from becoming loose or disconnected in use. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention generally includes a locking system for a connection between two parts, comprising a first part; a second part for connection with the first part; and an interfering member, the member constructed and arranged to permit connection and thereafter, to prevent separation of the parts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0008]      FIG. 1  is a partial section view of a male and female part prior to connection. 
           [0009]      FIG. 2  is a partial section view of the parts during connection. 
           [0010]      FIG. 3  is a partial section view of the parts threadedly connected together and locked together with a snap ring. 
           [0011]      FIG. 4  is a partial section view showing another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIG. 1  is a partial section view of two parts  100 ,  200  to be mated together. A first part  100  includes a threaded portion  110  having male threads and a second part  200  has mating female threads  210 . The threads in the embodiment shown are typical, and the first part includes a tapered nose portion  120  to facilitate the initial mating of the parts before the threads  110 ,  210  are engaged by relative rotation between the parts. 
         [0013]    In addition to the male threads  110 , the first part  100  includes a resilient member in form of a snap ring  300  disposed on its outer diameter in a groove  125  formed to house the ring ( FIG. 2 ). The snap ring  300  and groove  125  are designed and chosen whereby the ring fits in the groove and an outer portion of the ring extends from the groove to form a shoulder  310 , thereby increasing the outer diameter of the first component  100  in the area of the ring. 
         [0014]    Snap rings or retaining rings are known in the art and are essentially a fastener for holding a second component on a first component, especially when installed in a groove. Once installed, the exposed portion acts as a shoulder which retains the second component, especially when the mating component has a matching groove to house the outer surface of the ring while the inner surface of the ring remains housed around the groove in the first component. Snap rings are typically made from carbon steel or stainless steel and may feature a variety of finishes for corrosion protection, depending on the type of environment in which they are used. 
         [0015]    In installation, the snap ring is designed to be slid over the threads  110  and tapered portion  120  of the first part  100  until it reaches the groove  125 . As the ring is passed onto the part, it expands due to a gap  315  provided in the body of the ring and then “snaps” into the groove  125 . 
         [0016]      FIG. 2  is a partial section view of the parts  100 ,  200  during connection. As shown by arrow  20 , the first component is rotated via the threaded connection between the parts, and axial motion (arrow  10 ) is transmitted by the threads. In  FIG. 2 , the parts are partially threaded together to a point whereby the snap ring  300  and groove  125  of the first part is approaching a groove  225  formed in an inner diameter of the second part  200 . As shown, a tapered opening  230  in the second part is compressing the ring  300  (arrows  305 ), thereby reducing its circumference by reducing the size of gap  315 . The connection is constructed and arranged whereby the snap ring  300  axially fixes the two parts  100 ,  200  together at a point wherein the threaded connection is essentially complete. The space between the ring  300  and the groove  225  of the second part and between the end of the male threads  110  and the female threads  210  illustrate the connection is not yet completed. 
         [0017]    In  FIG. 3  the threaded connection is completed, and the snap ring  300  has met and expanded (arrows  306 ) into the groove  225  formed in an inside diameter of the second part  200 . As shown, a space  126  now exists between the inside diameter  301  of the expanded snap ring  300  and an outer surface groove  125 . 
         [0018]    In one embodiment, the locking system is utilized in the following manner: A resilient member  300  is installed on a first part  100  of a component for use downhole. Installation is complete when the resilient member is housed in a preformed groove  125  formed in an outer diameter of the first part  100 . Thereafter, the first and second portions are threaded together using mating threads formed on each. At a point when the threaded connection is made, the resilient member, whose diameter is decreased as the first portion moves into the second portion, finds and snaps into a mating groove  225  formed on the inside surface of the second part  200 . Once the ring is retained in the grooves  125 ,  225  a slight amount of rotation might be possible between the parts  100 ,  200  but not enough to permit axial movement therebetween. 
         [0019]      FIG. 4  is a partial section view showing another embodiment of the invention. As with the previous embodiment, a first  100  and second  200  parts are joined together with male and female threads. There is also a groove  125  in the first part for initially housing the ring and a mating groove  225  in the second part to receive the ring as the threading of the parts is completed. However, unlike the previous embodiment, two rings  400   a,    400   b  are provided, each typically having the same dimensions and thickness. While each ring includes a gap  315  (not shown) the gaps of each ring need not be rotationally aligned. In the embodiment shown, the rings are about ½ the thickness of the rings used in the previous embodiment meaning that the grooves into which they fit are the same width and depth in both examples. Utilizing two rings rather than one provides some redundancy in case one ring fails during assembly. 
         [0020]    In addition to an additional ring, the embodiment of  FIG. 4  includes a resilient member like spring that is placed in the inner end of the second part in a manner that causes it to be compressed as the connection is made. Preloading devices like springs are well known for preventing threaded connections from “backing off” after the connection is made. 
         [0021]    In each of the forging examples, interference created between the ring or rings and the grooves of parts  100 ,  200 , the threaded connection and any resilient member the connection is essentially locked with little or no axial or rotational movement possible between the parts. Because the locking structure is internal to the connection, it is protected from damage as the downhole component is run in and removed from the wellbore and, in the case of a plunger for a downhole pump, as it reciprocates up and down in the well. 
         [0022]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. For example, any number of rings can be used and the grooves and resilient members need not be strictly circumferential so long as there is an interference between the parts preventing their rotation due to a third member internally housed in the connection between the parts when they are threaded together.