Patent Application
20150069676
1. Field of the Invention
This invention relates to an improved sacrificial exothermic cutting blade that is used in a standard oxygen exothermic cutting torch for cutting a variety of materials on land and underwater. The improved cutting blade is adapted to easily and reliably cut both wide and narrow kerfs by using different flat and curved portions of a semi-flattened outer tube.
2. Background Art
Exothermic cutting tools are employed on land and underwater for cutting structural materials such as rock, stone, concrete, iron and steel. Examples of conventional cutting rods are available by referring to U.S. Pat. Nos. 4,069,407; 4,182,947; 3,507,231; 3,487,791; 3,500,744; 3,507,230; 3,570,419; and 3,738,288. The exothermic cutting rods shown in the foregoing patents all have a cylindrical outer tube and a plurality of elongated fuel rods or wires held in place by tube crimps. The result is a rod of oxidizable metal used for cutting, gouging and piercing. Oxygen is driven through the cylindrical tube filled with wires, and the rod is subsequently ignited with a catalytic spark. The resulting flame is brought into contact with the structural material to be cut. Older exothermic cutting rods contained a mixture of steel and alloys like aluminum and magnesium to maintain combustion. The exothermic cutting rods commonly used today contain low carbon steel, allowing the flame to extinguish once oxygen flow is abated. Since oxygen is driven at 80 to 100 pounds psi through existing exothermic cutting rods to maintain combustion, single and multiple crimps are applied to the cylindrical outer tube to secure the internal fuel wires in position while the tube and wires are consumed during the cutting process. Wire combinations vary from a complete fill of the tube to a radial configuration with the center wire removed. Both designs experience problems in both cutting performance and reliability.
The tube crimps which secure the inner fuel wires unavoidably cause venturi-related effects. High pressure oxygen passing crimps causes vacuum-related turbulence. To counteract the negative consequences of uneven oxygen flow, oxygen pressures are typically elevated, exaggerating flare outs, fluttering, side burns and wire stub outs. In particular, the velocity of high pressure oxygen slows when encountering the crimps and rapidly increases after the crimps so as to cause an uneven vacuum. The greater the number of crimps, the greater the exaggerated negative effects. Since exothermic cutting rods contain multiple crimps to hold the fuel wires intact at high oxygen pressures, the exothermic flame suddenly stops, because oxygen turbulence disrupts and extinguishes the flame. One variation of flare outs is fluttering. In this case, the flame flutters which results in significantly reduced cutting efficiency and frequent flare outs. Uneven oxygen flow causes the cutting tube to burn unevenly up one side allowing oxygen to escape prior to the burn zone. Cutting efficiency is therefore significantly reduced and the rod is generally rendered unusable. Uneven oxygen flow causes inadequate combustion of the fuel wires leaving a portion of the wires protruding from the cutting end of the tube. The protruding wires prevent placing the exothermic cutting rod directly into the cutting kerf which renders the cutting rod unusable.
There is currently no method to narrow the cutting kerf because of the uniform diameter of the round tube. Round exothermic cutting rods cut a kerf (width) slightly larger than the diameter of the cylindrical rod. A ⅜ inch diameter round exothermic cutting rod will cut a slightly larger kerf in the hands of an experienced user. When users wish to cut a smaller kerf, a smaller diameter cutting rod is required which necessitates both additional inventory and that additional time be expended to exchange torch collets in order to be able to accommodate the new size.
In general terms, an improved sacrificial exothermic cutting blade is described to be carried by a standard oxygen exothermic cutting torch for use in cutting structural materials on land and underwater. The cutting blade includes a semi-flattened outer tube at a first end thereof having a substantially oval shape such that a major axis along the height of the tube is longer than a minor axis along the width. The cutting blade includes a short cylindrical portion at its opposite end to be received by a collet of the torch. A plurality of conventional consumable fuel rods or wires runs longitudinally through the flattened outer tube of the rod.
Because of its semi-flattened shape, the outer tube of the rod has curved (i.e., rounded) top and bottom cutting surfaces and relatively flat side cutting surfaces. By virtue of the foregoing, the improved cutting blade has the ability to reliably cut a narrow kerf using one of the curved top or bottom cutting surfaces or a wider kerf using one of the relatively flat side cutting surfaces. In this same regard, the improved exothermic cutting blade will consume less oxygen and experience less flare outs, fluttering, side bums and stub outs than conventional tubular cutting rods having a cylindrical outer tube.
The semi-flattened outer tube 3 of cutting blade 1 is created by means of locating the usual cylindrical tube in a press and applying a compressive force to one end thereof until a desired flattened shape is achieved. The resulting cutting blade 1 has relatively flat side cutting surfaces 12 and 14 lying opposite one another and curved (i.e., rounded) top and bottom cutting surfaces 16 and 18 lying opposite one another. It is also to be understood that the locations of the sides of the blade 1 are interchangeable with the top and the bottom thereof. By way of one example only, the semi-flattened outer tube 3 has a height along its major axis 5 of about 10.0 mm and a width along its minor axis 7 of about 7.0 mm. The opposite end 19 of the cutting blade 1 remains cylindrical to fit within a standard torch collet (best shown in
A significant advantage provided by the semi-flattened exothermic cutting blade 1 is its ability to cut a narrow kerf using a curved top or bottom cutting edge 16, 18 of the cutting blade or a wide kerf using a relatively flat side cutting edge 12, 14. By way of further example, a cutting blade like that shown in
In addition to lower oxygen consumption, flare outs, fluttering, side burns and stub outs will be better avoided. The fuel wires 10 inside the semi-flattened tube 3 form a tight bundle seal against the tube walls which provides enhanced flow characteristics by virtue of the oxygen channels that are created during combustion. It has been found that the improved exothermic cutting blade 1 efficiently cuts ¼ inch material (e.g., both ferrous and non-ferrous metals) with as little as twenty pounds oxygen. Conventional cylindrical exothermic cutting rods are known to operate at eighty pounds oxygen pressure or greater merely to sustain combustion. The improved cutting blade 1 provides greater control and less oxygen consumption overall. The semi-flattened shape of the blade also allows for easier ignition because of its narrowed surface area across the burn horizon. As an additional benefit, the flattened shape of the outer tube 3 of cutting blade 1 prevents rolling along ship decks while being deployed in offshore cutting applications.
Comparative tests have shown that the improved exothermic cutting blade 1 of this invention facilitates making long cuts due to a focused linear flame configuration, while allowing low pressure cuts to be made with precision and longer burn duration. The economic advantages of the cutting blade 1 in terms of materials, labor, cutting performance and cutting reliability are significant and make the cutting blade ideally suited for repair, maintenance, scrap, dismantling and salvage assignments on land as well as in underwater marine settings.
