Slip Assembly for Handling a Tubular

Abstract

A slip assembly for handling a tubular, such as drill pipe, is disclosed. In one embodiment, the slip assembly includes a slip bowl having slip segments inserted therein. Each of the slip segments includes a force amplifier member slidably disposed to a slip member. An amplifier is disposed within a pocket formed at the slip member, and upon actuation, the amplifier decreases the angle of inclination of the slip assembly with respect to the tubular. A pad base is secured to the force amplifier member and configured to contact the tubular. The pad base includes a frictional material.

What is claimed is: 
     
         1 . A slip assembly for handling a tubular comprising:
 a slip bowl having an upper end and a lower end and a tapered axial bore therethrough;   a plurality of slip segments for insertion into the slip bowl, each slip segment including an upper end and a lower end and an inner surface which defines the shape of the axial bore; and   each of the slip segments including:
 a slip member having a first tapered inner slip surface, a first tapered outer slip surface, and a pocket at the tapered inner slip surface, the first tapered outer slip surface is slidably disposed on the slip bowl, 
 a force amplifier member having an upper contact surface, a second tapered inner slip surface, a second tapered outer slip surface, and a downwardly facing shoulder on the second tapered outer slip surface at the pocket, the upper contact surface disposed against a limiting plate, the second tapered outer slip surface is slidably disposed on the first tapered inner slip surface, 
 a force amplifier disposed within the pocket, upon actuation, the force amplifier decreasing the angle of inclination of the slip assembly with the tubular, and 
 a pad base having a frictional material thereon disposed on the second inner slip surface of the force amplifier member. 
   
     
     
         2 . The slip assembly as recited in  claim 1 , wherein the second tapered inner slip surface of the force amplifier member and the pad base are coupled by a linear movement connection limiting linear movement in a pre-defined direction. 
     
     
         3 . The slip assembly as recited in  claim 1 , wherein the second tapered inner slip surface of the force amplifier member and the pad base are coupled by a dovetail joint connection limiting linear movement in a pre-defined direction. 
     
     
         4 . The slip assembly as recited in  claim 1 , wherein the force amplifier member further comprises a spring and a sliding cylinder. 
     
     
         5 . The slip assembly as recited in  claim 1 , wherein the force amplifier member rests against the limiting plate when biased by the amplifier. 
     
     
         6 . The slip assembly as recited in  claim 1 , wherein the force amplifier decreases the angle of inclination of the slip assembly with the tubular by 1 degree to 5 degrees. 
     
     
         7 . The slip assembly as recited in  claim 1 , wherein the force amplifier decreases the angle of inclination of the slip assembly with the tubular by 3 degrees. 
     
     
         8 . The slip assembly as recited in  claim 1 , wherein the frictional material increases the coefficient of friction between the slip assembly and the tubular. 
     
     
         9 . The slip assembly as recited in  claim 1 , wherein the frictional material provides a coefficient of friction of about 0.15. 
     
     
         10 . A slip assembly for handling pipe assemblies on a drilling rig having a rotary table, the slip assembly comprising:
 a slip bowl supported in the rotary table having an upper end and a lower end and a tapered axial bore therethrough for passage of the drill pipe, the tapered axial bore having a constant slope from the upper end to the lower end;   a plurality of slip segments for insertion into the slip bowl, each slip segment including an upper end and a lower end and an inner surface which defines the shape of the axial bore for passage of the drill pipe;   each of the slip segments including:
 a slip member having a first tapered inner slip surface, a first tapered outer slip surface, and a pocket at the tapered inner slip surface, the first tapered outer slip surface is slidably disposed on the slip bowl, 
 a force amplifier member having an upper contact surface, a second tapered inner slip surface, a second tapered outer slip surface, and a downwardly facing shoulder on the second tapered outer slip surface at the pocket, the upper contact surface disposed against a limiting plate, the second tapered outer slip surface is slidably disposed on the first tapered inner slip surface, 
 a force amplifier disposed within the pocket, upon actuation, the force amplifier decreasing the angle of inclination of the slip assembly with the tubular, and 
 a pad base having a frictional material thereon disposed on the second inner slip surface of the force amplifier member. 
   
     
     
         11 . The slip assembly as recited in  claim 10 , wherein the second tapered inner slip surface of the force amplifier member and the pad base are coupled by a linear movement connection limiting linear movement in a pre-defined direction. 
     
     
         12 . The slip assembly as recited in  claim 10 , wherein the second tapered inner slip surface of the force amplifier member and the pad base are coupled by a dovetail joint connection limiting linear movement in a pre-defined direction. 
     
     
         13 . The slip assembly as recited in  claim 10 , wherein the force amplifier member further comprises a spring and a sliding cylinder. 
     
     
         14 . The slip assembly as recited in  claim 10 , wherein the force amplifier member rests against the limiting plate when biased by the amplifier. 
     
     
         15 . The slip assembly as recited in  claim 10 , wherein the force amplifier decreases the angle of inclination of the slip assembly with the tubular by 1 degree to 5 degrees. 
     
     
         16 . The slip assembly as recited in  claim 10 , wherein the force amplifier decreases the angle of inclination of the slip assembly with the tubular by 3 degrees. 
     
     
         17 . The slip assembly as recited in  claim 10 , wherein the frictional material increases the coefficient of friction between the slip assembly and the tubular. 
     
     
         18 . The slip assembly as recited in  claim 10 , wherein the frictional material provides a coefficient of friction of about 0.15. 
     
     
         19 . A slip assembly for handling a tubular comprising:
 a slip bowl having an upper end and a lower end and a tapered axial bore therethrough;   a slip member having a first tapered inner slip surface, a first tapered outer slip surface, and a pocket at the tapered inner slip surface, the first tapered outer slip surface is slidably disposed on the slip bowl;   a force amplifier member having an upper contact surface, a second tapered inner slip surface, a second tapered outer slip surface, and a downwardly facing shoulder on the second tapered outer slip surface at the pocket, the upper contact surface disposed against a limiting plate, the second tapered outer slip surface is slidably disposed on the first tapered inner slip surface;   a force amplifier disposed within the pocket, upon actuation, the force amplifier decreasing the angle of inclination of the slip assembly with the tubular, the force amplifier member resting against the limiting plate when biased by the amplifier;   a pad base having a frictional material thereon disposed on the second inner slip surface of the force amplifier member; and   the force amplifier member and the pad base are coupled by a dovetail joint connection limiting linear movement in a pre-define direction.   
     
     
         20 . The slip assembly as recited in  claim 19 , wherein the force amplifier decreases the angle of inclination of the slip assembly with the tubular by 1 degree to 5 degrees.