FUSION BONDED EPOXY REMOVAL TOOL

A tool for removing fusion bonded epoxy coating from the surface of a pipe has an elongate rotatable shaft suitable for being received in a rotating tool holder of a machine. Extending radially outward of the distal end of the shaft are a plurality of fingers, the outer ends of which are spaced apart. Each of the fingers is made of a spring metal, and at the distal end of each finger is an abrasive pad having diamond particles embedded in soft metal. Spring force is independently applied by each spring finger to its associated abrasive pad.

BACKGROUND OF THE INVENTION

With the advent of offshore drilling and the transportation of liquids such as gas and oil through underwater pipes robotically operated machines are needed to repair pipes that extend through deep waters. Such pipes are electrically connected along their length. They also have a coating of fusion bonded epoxy on their outer surface to protect the metal of the pipe from corrosion caused by the chemicals in the ocean. To repair a submerged pipe, the pipe must first be cut in two locations to remove a defective portion, after which the disconnected ends of the undamaged portions must be prepared to receive a repaired length of pipe. One of the steps needed to prepare the end of a length of pipe is to remove a portion of the fusion bonded epoxy coating from the outer end of the pipe in order that a good electrical connection may be made through the repair length. Also, the manufacturers of the couplings that attach the repair length to the existing pipe do not guarantee a tight seal unless the fusion bonded epoxy is removed from the repair area.

Currently, the fusion bonded epoxy coating for underwater pipes is removed by providing a rotating drum, the outer surface of which has embedded therein hard particles of tungsten carbide. The surface of the drum is applied to the surface of the pipe and the drum rotated causing the tungsten carbide particles to remove the fusion bonded epoxy.

It has been found that it is difficult to apply the desired force of the drum against the outer surface of a pipe having an epoxy surface because of the weight of the drum itself. Where the drum is to remove epoxy from the upper surface of the pipe, the weight of the drum may exceed the force desired to be applied to the surface and therefore the machine rotating the drum must compensate for the weight being applied. Conversely, where the drum is rotated against the lower surface of a pipe, the machine that rotates the drum must apply a force greater than the drum weight against the lower surface of the pipe to overcome the weight of the drum and provide sufficient force to remove the epoxy surface. Similar problems exist where the drum is applied against a horizontal portion of the pipe. Furthermore, it has been found that the tungsten carbide particles that are embedded in the drum tend to cause excess damage to the metal of which the pipe is made. Accordingly, there is a need for an improved tool for removing an epoxy bonded surface from a pipe, especially where the pipe is submerged.

BRIEF DESCRIPTION OF THE INVENTION

Briefly, the present invention is embodied in a tool having an elongate rotatable shaft suitable for being received in a rotating tool holder of a machine. Extending radially outward of the distal end of the shaft are a plurality of fingers, the outer ends of which are spaced apart.

In accordance with the invention, one of the fingers is made of a spring metal, and at the outer end of the finger is an abrasive pad having a plurality of diamond particles embedded therein.

In the preferred embodiment, each of the fingers is made of a spring metal, and at the distal end of each finger is an abrasive pad having diamond particles embedded in soft metal. Accordingly, a spring force is independently applied by each spring finger to its associated abrasive pad.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring toFIGS. 1 through 5, a tool in accordance with the present invention, a tool10is rotatably symmetric about an elongate shaft12having a rearward end14adapted for insertion into the retainer of a rotatable machine, not shown, a longitudinal axis15, and a threaded outer end16for threadedly retaining a working end18. For the purposes of this discussion the working end18of the tool10shall be considered the forward end of the tool10, and elements described herein that are directed axially toward the working end18shall be considered the forward end thereof and elements that are directed axially toward end14of shaft12shall be considered the rearward end thereof.

The working end18is generally disc shaped in appearance and includes a centrally located hub20having a planar forward surface22and a parallel planar rearward surface24. Extending rearwardly of the rearward surface24is a cylindrical projection26having opposing flats28,29. Extending axially through the body of the hub20and the projection26is a threaded cylindrical bore30sized to threadedly receive the forward end16of the shaft12. A hex jam nut32is also threaded on the forward end16of the shaft12before the hub20for locking the hub20to rotate with the shaft12. Extending around the circumference of the hub20are planetary parallel threaded bores34the centers of which define a circle that is concentric with the threaded bore30. In the preferred embodiment, the forward end of the shaft12does not extend beyond the forward surface22of the hub20.

Positioned adjacent the forward surface22of the hub20are first and second identically shaped star wheels36,38, each of which has a plurality of elongate fingers40. In the embodiment depicted, each star wheel36,38has nine identical fingers40, however it should be appreciated that the working end18of the tool can be made with more fingers or fewer fingers without departing from the spirit and scope of the invention. Each star wheel36,38is made of a spring steel and preferably has a thickness of about one-sixteenth of an inch. Each of the star wheels36,38also has a centrally located opening42and positioned around the central opening42are a plurality of spaced apart planetary holes44that are equal in number to the threaded bores34in the hub20. The planetary holes44define a circle coaxial with the central opening42of the star wheel and equal to the diameter of the circle defined by the planetary holes34of the hub20. The star wheels36,38are retained to the forward surface22of the hub20by a plurality of screws46-46sized to be slideably received in the holes44of the star wheels36,38and threadedly received in the bores34of the hub20. With the star wheels36,38secured to the forward end of the hub20, the fingers40of both star wheels36,38align with one another and thereby double the effective spring force provided to each of the star wheels independently.

At the outer end of each finger40of the aligned star wheels36,38are a pair of transverse holes48,50. Each of the fingers40has attached at its outer end a generally rectangular mounting plate52having threaded holes54therein sized and positioned to receive screws58-58. The screws58-58are fitted through the holes48,50at the distal end of each of the fingers40and into the threaded holes54of the mounting plates52for retaining the mounting plate52to the forward surface of each of the fingers40. The mounting plates52therefore formed in a planetary ring on the forward surface of star wheel38with each mounting plate at the distal end of each of the fingers40.

In accordance with the present invention, each mounting plate52has attached to the forward surface thereof an arcuate shaped diamond cutting segment60. The diamond cutting segments60are preferably made of a soft metal, such as silver or an alloy thereof with particles of diamond material62embedded into the soft metal. Each segment60is soldered or otherwise secured to the forward surface of one of the mounting plates52. The forward surface of each of the segments60can therefore be applied to the surface of a pipe to remove the fusion bonded epoxy on the outer surface thereof.

A removal tool10in accordance with the present invention that has a plurality of independently springed fingers40and a diamond cutting segment at the distal end of each finger which will independently move across the portion of the surface of a coated pipe. The diamond particles in the various segments60provide an abrasive surface suitable for removing the fusion bonded epoxy. After each segment has removed a portion of the epoxy layer, the spacing between adjacent fingers permits water to circulate around the individual segments60and wash accumulated debris from the surface of the segment before rotation again brings the segment60in contact with the surface of the pipe. Also, the provision of independently adjustable fingers40allows each finger to apply the force desired to remove the epoxy surface from a pipe. Furthermore, the spacings between the fingers allow a remote camera mounted on the machine retaining the tool10to view the underlying pipe between the passage of the successive fingers, such that an operator can view the operation of the tool without removing the tool from the work site. It has also been found that where the segments employ relatively small particles of diamond, the hard cutting material does not unduly damage the outer surface of the pipe as was the case with a removal tool that employed tungsten carbide inserts.

While the present invention has been described with respect to a single embodiment, it will be appreciated that many modifications and variations can be made without departing from the spirit and scope of the invention. It is therefore the intent of the appended claims to cover all such modifications and variations that fall within the spirit and scope of the invention.