Downhole tool

Abstract

A downhole tool comprises a body having a slot therein, a cutting blade mounted within the body and extendible and retractable through the slot such that the outer diameter of the tool can be selectively increased, an actuation member for driving the cutting blade between the retracted and extended positions and a mounting means connecting the blade to the actuation member, said body having a tapered surface along which the blade travels such that as the blade travels along the tapered surface the blade moves radially outwardly with respect to both the body and the mounting means whilst remaining in contact with the tapered surface.

1 . A downhole tool comprising:
 a body having a slot therein;   a cutting blade mounted within the body and extendible and retractable through the slot such that the outer diameter of the tool can be selectively increased;   an actuation member for driving the cutting blade between the retracted and extended positions;   a mounting means connecting the blade to the actuation member; and   said body having a tapered surface along which the blade travels such that as the blade travels along the tapered surface the blade moves radially outwardly with respect to both the body and the mounting means whilst remaining in contact with the tapered surface.   
     
     
         2 . A downhole tool according to  claim 1 , wherein the tool comprises a plurality of slots and a plurality of cutting blades, each blade being extendible and retractable through a respective slot in the body. 
     
     
         3 . A downhole tool according to  claim 2 , wherein the slots are equispaced around the outer surface of the body. 
     
     
         4 . A downhole tool according to  claim 1 , wherein the or each slot in the body extends longitudinally along the length of the body. 
     
     
         5 . A downhole tool according to  claim 1 , wherein the mounting means comprises a substantially rectangular block 
     
     
         6 . A downhole tool according to  claim 5 , wherein the block is formed with a T-slotted head at one end. 
     
     
         7 . A downhole tool according to  claim 6 , wherein the cutting blade comprises a recess at one end which receives the T-slotted head of the block. 
     
     
         8 . A downhole tool according to  claim 5 , wherein the depth of the or each cutting blade is greater than the depth of the block. 
     
     
         9 . A downhole tool according to  claim 1 ,  wherein the cutting blade(s) and body are slidably connected together. 
     
     
         10 . A downhole tool according to  claim 1 , wherein the or each blade is fixed along one longitudinal edge to the body. 
     
     
         11 . A downhole tool according to  claim 1 , wherein a channel is formed in one of the underside of the cutting blade and the tapered surface of the body 
     
     
         12 . A downhole tool according to  claim 11 , wherein a cooperating leg is formed on the other of the cutting blade and tapered surface of the body, the leg being slidably constrained within the channel to prevent the blade being lifted out of engagement with the body as the blade slides longitudinally along the tapered surface. 
     
     
         13 . A downhole tool according to  claim 1 , wherein the mounting block further comprises a jetting nozzle. 
     
     
         14 . A downhole tool according to  claim 1 , wherein the mounting block is fixed to the actuation member. 
     
     
         15 . A downhole tool according to  claim 1 , wherein the actuation member comprises a sleeve. 
     
     
         16 . A downhole tool according to  claim 15 , wherein the sleeve is slidably mounted within the body of the tool and is selectively operable between a retracted and an extended position within the body. 
     
     
         17 . A downhole tool according to  claim 15 , wherein the sleeve is operated by a drop ball mechanism. 
     
     
         18 . A downhole tool according to  claim 1 , wherein the tapered surface comprises a ramp. 
     
     
         19 . (canceled)