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Earthboring tool and method of casehardening

Earthboring tool and method of casehardening description/claims

1. Field of the Invention

This invention relates generally to earthboring tools for cutting earthen annulus.

2. Description of the Related Art

Earthboring tools are commonly used to bore holes by cutting through earthen annulus. Such holes may be bored for many different reasons, such as drilling for oil, minerals and water. One type of earthboring tool used for boring is a rotary earth bit. Several examples of rotary earth bits are disclosed in U.S. Pat. Nos. 3,550,972, 3,847,235, 4,136,748, 4,427,307, 4,688,651 and 4,741,471. A rotary earth bit generally includes one or more earth bit cutting cones rotatably mounted to corresponding lugs with a hub unit, as well as ball and roller bearings. The lugs generally form a portion of an earth bit body and, as the earth bit body rotates, the cutting cone rotates in response to contacting earthen annulus.

Another type of earthboring tool is a mechanized boring cutter, with an example being disclosed in U.S. Pat. No. 4,040,493. A mechanized boring cutter generally includes a hub unit rotatably mounted to a shaft and a cutting cone frictionally engaged with the hub unit. The hub unit is often rotatably mounted to the shaft using ball bearings.

It is known that earthboring tools wear out with use. As a result, they are often casehardened to reduce the amount of wear they experience. Examples of casehardened earthboring tools are disclosed in U.S. Pat. Nos. 4,303,137, 4,627,882, 4,643,051, 4,660,444 and 4,781,770. Casehardening sometimes involves subjecting the earthboring tool to a carburization process. However, there are several problems with using a carburization process.

A carburization process is typically a “batch process”, wherein a number of earthboring tool components are heated by a large and expensive furnace at the same time. The components are heated at the same time because it is not economical, or otherwise beneficial, to heat fewer components using a carburization process. Since the components are heated at the same time, they are casehardened in the same way without providing an option for selective casehardening. Further, the region of the earthboring tool component that is casehardened is often casehardened non-uniformly so its hardness undesirably varies from one location to another.

The carburization process also requires a long period of time. The furnace can provide temperatures in excess of 1700° F., resulting in a carburization process that can take ten or more hours. After the earthboring tool component is heated by the furnace, it is generally slow cooled, quenched and machine finished, which requires additional time.

Another problem is that the earthboring tool components typically include low alloy carbon steel, wherein the amount of carbon is generally less than one-quarter of one percent. Low alloy carbon steel often wears down faster than higher alloy carbon steel, so low alloy carbon steels are often case carburized to allow them to function with acceptable wear in earthboring tools. During the case carburizing process, the amount of carbon in the surface of the steel is increased by introducing an expensive carbon rich gas into the atmosphere in the furnace when the batch of earthboring tool components is being heated.

Other methods of casehardening involve using gas lasers that emit light or electron emitters that emit electrons. However, gas lasers and electron beam emitters are expensive and difficult to accurately align with the earthboring tool. They are difficult to align because they are unwieldy and the alignment often requires mirrors. Hence, it is desirable to provide other casehardening methods that are simpler, more time efficient and less costly.

The present invention provides a method of casehardening an earthboring tool component. The method includes steps of providing a first earthboring tool component and a semiconductor light emitting device carried by a mechanical arm. The method also includes a step of directing light emitted by the light emitting device to a first surface of the first earthboring tool component, wherein the first surface is casehardened in response to being heated by the light. The properties of the light are chosen so that the amount of time needed to caseharden the first earthboring tool component is significantly reduced.

In some situations, the light emitting device is moved, using the mechanical arm, so that a second surface of the first earthboring tool component is exposed to the light and casehardened in response. In some situations, the first earthboring tool component is moved so the light is provided to the second surface. In this way, selected surfaces of the first earthboring tool component are casehardened.

In some embodiments, the first earthboring tool component is replaced with a second earthboring tool component. In this way, the first and second earthboring tool components can be casehardened separately and provided with different amounts of casehardening. The second earthboring tool component is exposed to light emitted by the light emitting device so that a surface of it is casehardened. The first and second earthboring tool components can be coupled together to form an earthboring tool. The first and second earthboring tool components are often coupled together so that their casehardened surfaces face each other. In this way, these surfaces experience less wear when they engage each other.

These and other features, aspects, and advantages of the present invention will become better understood with reference to the following drawings and description.

FIGS. 1a and 1b are side views of a semiconductor light emitting device carried by a mechanical arm and directed at an earthboring tool component, in accordance with the invention.

FIG. 2a is a perspective view of a rotary earth bit which can be casehardened, in accordance with the invention.

FIG. 2b is a cross-sectional view taken along a cut-line 2b-2b of the earth bit of FIG. 2a.

• Provisional Patent
• Utility Patent

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