Cutter assembly

Abstract

There is a cutter assembly for a roller reamer for downhole drilling. The cutter assembly has a first end block and a cutting element having a plurality of cutting projections. The cutting element is rotatably mounted to the first end block. The cutter assembly further has (a) a primary locking assembly having a primary bore in the first end block for screwing in a primary screw to attach the cutter assembly to a reamer body and (b) a secondary locking assembly. The secondary locking assembly has a secondary bore in the first end block having a threaded section and a secondary bolt screwed into the threaded section. The secondary bolt has a head and a threaded portion. The secondary bolt is for unscrewing out such that the head is received in a locking bore of the reamer body to attach the cutter assembly to the reamer body.

1 . A cutter assembly for a roller reamer for downhole drilling, the cutter assembly comprising:
 a first end block;   a cutting element comprising a plurality of cutting projections, wherein the cutting element is rotatably mounted to the first end block;   wherein the cutter assembly further comprises:   a primary locking assembly comprising a primary bore in the first end block for screwing in a primary screw to attach the cutter assembly to a reamer body; and   a secondary locking assembly comprising:
 a secondary bore in the first end block comprising a threaded section; and 
 a secondary bolt screwed into the threaded section, the secondary bolt comprising a head and a threaded portion, wherein the secondary bolt for unscrewing out such that the head is received in a locking bore of the reamer body to attach the cutter assembly to the reamer body. 
   
     
     
         2 . The cutter assembly of  claim 1 , further comprising a biasing member arranged to bias the secondary bolt in an unscrewing direction. 
     
     
         3 . The cutter assembly of  claim 2 , wherein the biasing member is a spring arranged in the secondary bore. 
     
     
         4 . The cutter assembly of  claim 1 , wherein the secondary bolt further comprises a radial projection between the head and the threaded portion, wherein the radial projection shoulders against the reamer body to prevent the secondary bolt from unscrewing further. 
     
     
         5 . The cutter assembly of  claim 1 , further comprising a second end block, and wherein the cutting element is rotatably mounted between the first end block and the second end block. 
     
     
         6 . The cutter assembly of  claim 5 , wherein the primary locking assembly further comprises a primary bore in the second end block for screwing in a primary screw to attach the cutter assembly to the reamer body. 
     
     
         7 . The cutter assembly of  claim 1 , wherein each end block is a cutter block comprising a plurality of cutting projections. 
     
     
         8 . The cutter assembly of  claim 1 , wherein the secondary bore comprises a counter-bore section for receiving the head of the secondary bolt screwed into the threaded bore such that the head is flush with an outer surface of the first end block. 
     
     
         9 . The cutter assembly of  claim 1 , wherein the primary bore is transverse to the secondary bore. 
     
     
         10 . The drilling assembly of  claim 9 , wherein the primary bore is perpendicular to the secondary bore. 
     
     
         11 . A roller reamer comprising:
 the cutter assembly of  claim 1 ;   a reamer body comprising:
 a recess for receiving a cutter assembly; 
 a primary receiving bore for receiving the primary screw when it is screwed in to retain the cutter assembly in the recess; and 
 a secondary receiving through bore extending from an outer surface of the reamer body to the recess for receiving the head of the secondary bolt when it is unscrewed out to retain the cutter assembly in the recess. 
   
     
     
         12 . The roller reamer of  claim 11 , wherein the primary bore is transverse to the secondary bore. 
     
     
         13 . The roller reamer of  claim 12 , wherein the primary bore is perpendicular to the secondary bore. 
     
     
         14 . The roller reamer of  claim 11 , wherein the roller reamer comprises a plurality of cutter assemblies according to  claim 1 ,
 wherein the reamer body comprises:
 a plurality of recesses corresponding to the plurality of cutter assemblies; 
 a plurality of primary receiving bores corresponding to the plurality of recesses for receiving the corresponding primary screw when it is screwed in to retain the corresponding cutter assembly in the corresponding recess; and 
 a plurality of secondary receiving through bores corresponding to the plurality of recesses and each extending from an outer surface of the reamer body to the corresponding recess for receiving the head of the corresponding secondary bolt when it is unscrewed out to retain the corresponding cutter assembly in the corresponding recess. 
   
     
     
         15 . The roller reamer of  claim 14 , wherein the plurality of cutter assemblies are N cutter assemblies and the plurality of recesses are N recesses, and wherein the N recesses are arranged with N-fold rotational symmetry around the reamer body. 
     
     
         16 . The roller reamer of  claim 15 , wherein N is three. 
     
     
         17 . A method of assembly a roller reamer comprising the steps of:
 a. providing a cutter assembly according to  claim 1 ;   b. providing a reamer body comprising:
 a recess for receiving the cutter assembly; 
 a primary receiving bore for receiving the primary screw when it is screwed in to retain the cutter assembly in the recess; and 
 a secondary receiving through bore extending from an outer surface of the reamer body to the recess for receiving the head of the secondary bolt when it is unscrewed out to retain the cutter assembly in the recess, 
   c. inserting the cutter assembly into the recess;   d. screwing a primary screw through the primary bore into the primary receiving bore to retain the cutter assembly to the reamer body; and   e. unscrewing the secondary bolt until the head is within the secondary receiving through bore.   
     
     
         18 . The method of  claim 17 , further comprising:
 providing a plurality of cutter assemblies according to  claim 1 , and   wherein the reamer body comprises:   a plurality of recesses corresponding to the plurality of cutter assemblies;   a plurality of primary receiving bores corresponding to the plurality of recesses for receiving the corresponding primary screw when it is screwed in to retain the corresponding cutter assembly in the corresponding recess;   a plurality of secondary receiving through bores and corresponding to the plurality of recesses and each extending from an outer surface of the reamer body to the corresponding recess and for receiving the head of the corresponding secondary bolt when it is unscrewed out to retain the corresponding cutter assembly in the corresponding recess,   wherein the method further comprises carrying out steps c, d, and e for each corresponding recess and cutter assembly.   
     
     
         19 . The method of  claim 18 , wherein the plurality of cutter assemblies are N cutter assemblies and the plurality of recesses are N recesses, wherein the N recesses are arranged with N-fold rotational symmetry around the reamer body. 
     
     
         20 . The method of  claim 19 , wherein N is three.