Tube cutting apparatus and method

An improved apparatus for cutting the inside surface of a tube with a cutting means connected to a shaft means so that said cutting means cuts the tube by a flailing action, comprising:

• (a) a flexible connecting shaft connected to said cutting means and to said shaft means;
• (b) a substantially rigid support assembly connected to said shaft means having a distal end and a proximal end which is insertable within and slidably movable along the longitudinal axis of the tube;
• (c) a pressure operated, selectively expandable member connected to said support assembly for temporarily affixing said support assembly to the inside surface of the tube in order to position said cutting means adjacent to a selected point along the longitudinal axis of the tube, and
• (d) a guide bore within said support assembly for both journalling said shaft means and for conducting a pressurized fluid to said pressure operated, selectively expandable member.

An improved apparatus for cutting the inner wall of a tube with a cutting means having a flexible connecting shaft connected to a drive shaft which cuts the tube by a flailing action, comprising:

• (a) a substantially rigid support assembly having a distal and a proximal end which is slidably movable along the longitudinal axis of the tube, and which includes
• (i) a mandrel in its middle portion having a guide bore for journalling a linking shaft which links the flexible shaft of the cutting means to the drive shaft, and for providing a flow path for a pressurized fluid.
• (ii) a coupling means in its distal portion for detachably connecting the linking shaft to the flexible connecting shaft of the cutting means in order to facilitate the replacement of the cutting means,
• (iii) thrust bearing means for preventing the linking shaft from moving along the longitudinal axis of the guide bore during the cutting operation so that the cutting means cuts the inner wall of the tube in a thin circular pattern while producing a minimum amount of tube cuttings, and
• (iv) a coupling means in its proximal portion for detachably connecting the drive shaft to said linking shaft;
• (b) a resiliently expandable bladder circumscribing a portion of the mandrel and mounted thereto in fluid-tight relationship for temporarily affixing said support assembly to the inside surface of the tube in order to position the cutting means adjacent to a selected point along the longitudinal axis of the tube, wherein said expandable bladder communicates with a source of pressurized fluid at least in part through said guide bore in said mandrel, and
• (c) means located at the distal end of said support assembly for both journalling said linking shaft and for creating a fluid-tight seal between said linking shaft and said guide bore so that pressurized fluid introduced into the guide bore will be substantially directed into the expandable bladder.

A method for cutting a conduit by means of a cutting device having a substantially rigid support assembly slidably positionable along the longitudinal axis of the conduit, a linking shaft rotatably mounted within the support assembly, a cutting means having a blade means which is connected to one end of the linking shaft for cutting around the inner wall of the conduit, a flexible drive shaft connected to the other end of the linking shaft and surrounded by a flexible, fluid-tight casing, wherein said support assembly includes an expandable bladder which is selectively engageable with the inner surface of the conduit when a pressurized fluid is introduced into the bladder by way of the fluid-tight casing, comprising the steps of:

• (a) positioning the blade means adjacent to a point along the longitudinal axis of the conduit by slidably moving the support assembly of the device along the inside of the conduit by manipulating said casing surrounding the flexible drive shaft;
• (b) fixing said blade means into said position adjacent said point by introducing pressurized fluid into the expandable bladder through the fluid-tight casing until said bladder engages the inner surface of the conduit and secures said support assembly at a desired position within said conduit;
• (c) rotating the blade means by said drive shaft until said blade means cuts through said conduit;
• (d) stopping the rotation of said blade means;
• (e) disengaging said expandable bladder from the inside surface of said conduit by discharging said fluid from said bladder, and
• (f) removing said cutting device from said conduit.

A method for cutting a conduit by means of an improved flail tube cutter having an elongated cutting head circumscribed by a blade means, said cutting head being connected to a flexible connecting shaft, a substantially rigid support assembly which includes a linking shaft for couping the flexible connecting shaft to a drive shaft, as well as means for detachably mounting the support assembly, flexible connecting shaft and cutting head within the conduit, comprising the steps of

• (a) positioning the blade means of the cutting head adjacent to a selected point along the longitudinal axis of the conduit by slidably moving the support means, flexible connecting shaft, and cutting head along the longitudinal axis of the conduit;
• (b) detachably mounting the support assembly within the conduit after said blade means is positioned;
• (c) rotating said blade means at a speed no greater than about 15,000 rpm to avoid creating a flair around the cut end of the conduit after said conduit is cut, and
• (d) stopping the rotation of the blade means.