Abstract:
A under reamer that has two arms and is piston activated. The under reamer arms are supported on both side walls by a pin assembly. The under reamer arms are extended outward by a piston assembly which is spring biased to retract the arms. A surface of the under reamer arms adjacent the pivot point is protected via a holder assembly with a surface that matches the surface of the arms adjacent the pivot assembly.

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
       [0001]    Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
       BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to drilling devices used in, for example, the oil industry and, in particular, concerns an under reamer tool used to widen the diameters of bore holes. 
         [0004]    Description of the Related Art 
         [0005]    Drilling is commonly performed in industries such as the oil industry where holes are drilled into the ground to receive pipe. Similar holes are also drilled to receive pipe in water applications such as wells and the like. 
         [0006]    One tool that is commonly used is a tool known as an under reamer which extends down through a pipe and then has expandable arms so as to drill a bore hole that is wider than the diameter of the pipe. The arms are preferably expandable through the use of a hydraulic piston that causes the arms to extend outward from the central shaft of the tool. 
         [0007]    Typical under reamers used today have three arms spaced at equal intervals about the outer diameter of a vertical portion of the tool. The three arms are prone to breakage and also prone to vibratory movement as a result of smaller size and due to the design of the tool itself. 
         [0008]    Consequently, there is a need for an under reamer that is more robust in design and less prone to vibration than existing under reamers. 
       SUMMARY OF THE INVENTION 
       [0009]    The aforementioned needs are satisfied by the under reamer of the present invention which, in one non-limiting example or embodiment comprises an under reamer having a central shaft with two arms that are pivotable outward from the central shaft located at opposite sides of the central shaft. The arms are preferably pivotally mounted to the central shaft with a retaining pin formed on either side of the arms. The arms, in one non-limiting example have two lots that engage with the pivot pins. 
         [0010]    In another non-limiting example, the holder block engages with the upper end of the arms and a pivot pin extends through the arms and the central shaft to permit pivoting of the arms. In this example, the retaining pins are also located through the shaft to engage either side of the arms. The use of dual retaining pins reduces vibration and prolongs the life of the tool. Moreover, the use of two arms also prolongs the life of the tool as the arms can be formed to be larger size and therefore more robust. 
         [0011]    These and other objects and advantages will become more apparent from the following description taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIGS. 1A-1C  are isometric views of one exemplary embodiment of a dual precision under reamer of the present disclosure; 
           [0013]      FIGS. 2A and 2B  are isometric views of the arms of the under reams of  FIGS. 1A-1C ; 
           [0014]      FIGS. 3A and 3B  are holder blocks of the dual precision under reamer of  FIGS. 1A-1C ; 
           [0015]      FIGS. 4A and 4B  are retaining pins of the dual precision under reamer of  FIGS. 1A-1C ; 
           [0016]      FIGS. 5A and 5B  are a cross-sectional view of the under reamer of  1 A- 1 C that schematically shows the operating mechanism; 
           [0017]      FIG. 6  is a view of a cam member of the under reamer of  FIGS. 1A-1C ; and 
           [0018]      FIG. 7  is a front view of the under reamer of  FIGS. 1A-1C . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    Reference will now be made to the drawings wherein like numerals refer to like parts throughout.  FIGS. 1A and 1B  illustrate an exemplary dual precision under reamer  100  of one embodiment of the present invention. In this embodiment, the under reamer  100  includes a central shaft  102  that can be  44  inches long but this size may vary depending upon the application. A plurality of arms  104   a ,  104   b  which, in this case comprises two arms, extend pivotally outward from the central shaft  102 . The arms  104   a ,  104   b  are hydraulically activated so that a desired diameter of the bore hole can be selected. The end of the shaft  102  may also include a known digging implement. 
         [0020]    Digging implements  106  are formed on outer portion of the arm to facilitate digging of the bore hole. The arms  104   a ,  104   b  are retractable into openings  108  so that the under reamer  100  can be inserted through a pipe to the digging depth. The openings  108  may include cut outs  110  that are sized to receive the digging implements  106 . 
         [0021]    The arms  104   a ,  104   b  are shown in greater detail in  FIG. 2A and 2B . In this implementation, the arms  104   a,    104   b  have a pivot hole  112  on one end so as to be pivotally attached to the central shaft  102  in a manner that will be described in greater detail below. The arms  104  also have an outward digging surface  114 . As is also shown either of the side surfaces  116  of the arms include an arcuate groove  120  that receives a retaining pin in a manner that will be described in greater detail below. 
         [0022]    The arms  104  are secured in place via a pivot pin that extends through the pivot hole  112  and the central shaft  102 . Further, a holder block  130  is secured to the central shaft  102  and the holder block  130  defines an arcuate surface  132  that engages with a mating surface  134  on the arms  104  to reinforce the interaction between the arms  104  and the central shaft. 
         [0023]    A retaining pin component  140  is also attached to the central shaft via a mounting body  142  that is offset from a pin body  144 . The retaining pin body  144  is positioned within the arcuate grooves  120  on either side of the arms  104  so as to reduce vibration of the arms when the assembly  100  is rotated during digging operations. 
         [0024]    The relative positioning and functionality of these components are shown in greater detail in  FIGS. 5A and 5B . As shown, the shaft  102  defines an inner bore opening  150  that extends the length of the shaft  150 . The outer walls  152  of the shaft are relatively thick, e.g., on the order of approximately 3.75″ or 3.735″ inches thick in one non-limiting embodiment adjacent where the arms  104   a ,  104   b  are pivotally attached to the main shaft  10 . The openings  108  in the shaft that accommodate the arms  104  have exemplary dimensions of approximately 2.265 inches wide, approximately 16.750 inches long inches long and are spaced approximately 180 degrees about the outer circumference of the shaft  102 . As shown, the pivot openings  112  in the shaft that receive pivot pins and extend through pivot openings  113  in the arms  104  are positioned at an upper end of the openings  108 . 
         [0025]    As shown in  FIG. 2A , the arms  104   a ,  104   b  define an opening  160  that has a deeper flat portion  162  and an angled portion  164  that extends towards the outer end of the arms  104   a ,  104   b  that accommodates the digging implements  106 . In one implementation, the arms  104   a ,  104   b  are approximately 10.25 inches in length, approximately 2.25 inches in width, and approximately 2.75 inches in depth. The flat portion  162  of the opening  160  is approximately 1 inch deep and approximately 0.094 inches wide and the angled portion  162  extends at an approximately 25 degree angle with respect to the outer surface of the arms  104   a ,  104   b.    
         [0026]    The assembly  100  further includes a cam member  170  that is mounted inside the opening  150  in the shaft  102 . The cam member  170  is shown in greater detail in  FIG. 6 . The cam member  170  has an opening  172  that engages with a piston, in a manner that will be described in greater detail below, and two bearing arms  174   a ,  174   b  that are positioned within the openings  108  of the digging arms  104  in the manner shown in  FIGS. 5A and 5B . The cam member  170  also includes two positioning arms  176   a ,  176   b  that engage with the inner walls of the inner opening  150  of the shaft  102  to stabilize the cam member  170 . 
         [0027]    As shown in  FIGS. 5A and 5B , the cam member  170  is coupled to the shaft  182  of a piston  180  that is positioned within the opening  150  of the central shaft  102 . As the piston  180  is actuated, the cam member  170  is urged forward where the cam member bearing arms  172   a ,  174   b  engage with the angled portions  164  of the arms  108  which thereby urge the arms outward in the manner shown in  FIG. 5B . As such, the degree of deployment of the arms  108   a ,  108   b  away from the central shaft  102  is controllable by the extension of the shaft  182  of the piston  180 . 
         [0028]    As shown in  FIG. 5A and 5B , the shaft  102  has a reduced diameter portion  194  which defines an opening to receive the holder block  130  via bolts  192 . The arcuate surface  132  of the holder block  130  engages with the arcuate surface  134  of the arms  108   a ,  108   b  in the manner shown in  FIGS. 5A and 5B . The reduced diameter portion  194  also defines an opening  190  through which the shaft  182  of the piston  180  extends. The reduced diameter portion  194  also defines a flange  196  that is used to spring bias the piston shaft  182 . 
         [0029]    The piston shaft  182  includes a fastener  200  that extends through the piston shaft  182  and is connected to the cam  170 . The piston shaft  102  includes a thicker portion  202  that overlaps the flange  196  but is not as wide as the opening  150  of the shaft  182  so as to define gaps  204 . The thicker portion  202  of the piston shaft  182  includes a flange  206  that extends into the gaps  204  such that a spring  210  can be interposed between the flange  196  of the shaft  182  and the flange  206  of the thicker portion of the piston shaft  182 . The spring  210  biases the cam  170  into the position of  FIG. 5A  whereby removal of force from the piston on the shaft  180  results in the spring retracting the shaft  182  thereby returning the cam  170  to the deeper portion  162  of the arm  108   a ,  108   b  thereby retracting the arms  108   a ,  108   b  into the position of  FIG. 5A . The piston  180  can be similar to existing pistons of the prior art. 
         [0030]      FIG. 7  is a front view of the under reamer  100  which shows the relative positioning of the arms  104   a ,  104   b . As shown, the arms  104   a ,  104   b  are spaced so as to be 180 degrees apart from each other around the circumference of the shaft  102 . The use of two arms  104   a ,  104   b  permits this relative spacing. Further, the use of two arms  104   a ,  104   b  as opposed to the typical three in prior art devices permits the use of heavier arms  104   a ,  104   b  which lessens the chance the device can become disabled as a result of the arms breaking. Still further, the use of two arms results in greater side wall material that is supporting the arms and inhibiting twisting of the arms during digging operations. In one exemplary implementation, the shaft  102  is approximately 6″ in diameter and has walls having a thickness of approximately 2 to 3.75″ with the arms  104   a ,  104   b  being positioned approximately 180 degrees apart from each other about the circumference of the shaft  102 . 
         [0031]    It will be apparent from the foregoing description that various changes to the form, implementation and uses of the described embodiments may be made by those skilled in the art without departing from the sprit, teachings or scope of the instant application. Hence, the scope of the instant application should not be limited to the foregoing but should be defined by the appended claims.