Excavating – Digging edge – Specific material
Patent
1993-03-10
1994-12-27
Reese, Randolph A.
Excavating
Digging edge
Specific material
37453, 37195, E02F 928, B22F 708
Patent
active
053753500
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to excavating tools such as revolving cutter head excavators for use in mines or dredgers.
Revolving cutter head excavators consist of a drive wheel that rotates around a shaft and is driven by a means of rotation. The periphery of the revolving cutter head excavator has a series of buckets equipped with teeth arranged in directions that are essentially radial. Dredgers do not have buckets and their teeth are distributed around the periphery in a rotary ogival structure. Each tooth consists of a single-unit tooth body structure made of a mechanically resistant metal or alloy such as steel, having a fixing area to connect it to the bucket or the ogival structure and a working area to dig the soil. The working area is generally flat and shaped like a shovel and is bounded by a leading face that points in the direction of movement of the periphery of the wheel or ogival structure in the preferred direction of rotation and a trailing face or face opposite the leading face. The leading face and the trailing face are generally flat or slightly curved and are connected by a front tapered facet that defines a transverse cutting edge. If the tooth is mounted on the bucket or the ogival structure, the transverse cutting edge is essentially parallel to the axis of rotation of the assembly and the general plane formed by the tooth shovel or working area generally slants in the direction of the direction of movement of the tooth in the preferred direction of rotation.
During operation, part of the peripheral zone of the bucket or cutter cuts into the ground, the transverse cutting edge of the teeth bites into the ground and the leading face pushes up the material. This results in considerable wear of the transverse cutting edge and the leading face.
One common solution to increase the service life and the efficiency of the teeth is to hardface the external surface of the leading face and the tapered front facet in order to cover them with a coat of molten carbide by fusing a welding bead.
Although this process significantly increases the service life of the tooth, wear still occurs, relatively slowly at the start of use when the hard material still covers the front facet; wear then becomes much faster when the hard material that covers the front facet is itself damaged by wear. The tooth can only be used as long as the length of its working area has not reduced too extensively and this defines the maximum permissible area of wear of the tooth.
In particular, as soon as the front facet has lost its protective coating of hard material, wear becomes much faster despite the existence of a layer of hard material on the leading face of the tooth.
Another drawback of known structures is that they require the use of a protective surface hardfacing, a layer that is produced by melting with a welding torch or an electric arc. An examples of such a layer comprises a deposit consisting of a mixture of molten carbide particles embedded in a fusible matrix. Such hardfacing is time consuming and awkward and produces relatively irregular surfaces made up by the juxtaposition of several side-by-side welding beads. The intermediate areas between two successive beads are usually sunken areas of which the metallurgical structure is slightly different from the central structure of the welding beads. This results in a lack of homogeneity of the material that forms the protective layer made of a hard material and this results in the appearance of preferential areas of wear, thus encouraging faster wear of the material. In addition, such a process is expensive and requires skilled labor.
Dredger teeth with a composite structure are known consisting of a metal tooth body containing inserts of a hard anti-abrasion material. In document U.S. Pat. No. 3,805,423, a prefabricated insert is fitted in appropriate recesses in the metal tooth body where it is fixed by welding or brazing. The insert, in the embodiment shown in FIGS. 3 and 4, consists of two intermediate bars which each take up h
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Eilberg William H.
Reese Randolph A.
Technogenia S.A.
Warnick Spencer
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