Boring or penetrating the earth – With tool shaft detail
Reexamination Certificate
1999-03-24
2001-09-25
Batson, Victor (Department: 3673)
Boring or penetrating the earth
With tool shaft detail
C285S334000, C411S386000
Reexamination Certificate
active
06293360
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a thread joint, a male portion, a female portion and a method for manufacturing a thread product for use in percussive drilling equipment.
PRIOR ART
In a conventional thread joint between two components in a rock drilling equipment for percussive drilling, one normally uses male and female threads that have been formed by cutting, see for example Swedish Patent No. 469,602 corresponds to (U.S. Pat. No. 4,687,368). At manufacturing of such a male thread a blank of steel is formed, which comprises a thick part having ends that connect to a clearance surface or a clearance groove of less diameter to receive at least portions of the threading tool and to an often conical free end. Subsequently, the tool's lateral and longitudinal feed are coordinated with the rotational movement of the thick portion such as to generate the thread in a conventional manner during at least one pass. Sharp edges are formed at the entrance and exit ends of the thread due to the geometries of the clearance groove and the free end surface. Corresponding sharp edges are formed when cutting a female thread.
The sharp edges result in the male and female threads damaging each other foremost at the free end of the respective drilling element during mounting and dismounting of the joint.
In addition, the threads are case hardened, and the sharp edges become hardened so much that the sharp edges define the area for the deepest case depth of the thread. Results from the hardening show cracking and fatigue in these areas during drilling, and therefore the lifespan of the joint becomes relatively short.
Another conventional thread joint between two components in a rock drilling equipment for percussive drilling and experience cracking is shown in EP Document 02 220 147 wherein the thread end is cut away to form a uniform thread size from one end to the other.
OBJECTS OF THE INVENTION
One object of the present invention is to provide a thread joint of the above-indicated type in which a longer tool life is attained.
Another object of the present invention is to provide a thread joint including entrances and exits with substantially the same case depth as in the rest of the thread joint.
Still another object of the present invention is to provide a thread joint the parts of which do not damage each other during mounting and dismounting.
Still another object of the present invention is to provide strong male and female portions.
Still another object of the present invention is to provide a method for manufacturing rock drilling products that have strong thread starts.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a thread joint which includes first and second drill string components, the first component including a spigot. A substantially cylindrical external thread is formed in the spigot. A substantially cylindrical internal thread is formed in the second component. Each of the internal and external threads includes an end section gradually transforming into a full thread section. The end section has a pair of flanks, and the full thread section also has a pair of flanks. In at least one of the internal and external threads, both flanks of the end section have different profiles than the corresponding flanks of the full thread section.
The invention also pertains to percussive drilling components having an external thread or an internal thread of the above-described type.
The invention also pertains to a method of manufacturing a percussive drilling component having a thread. The thread includes an end section gradually transforming into a full thread section. Each of the end and full thread sections includes two flanks. The method comprises the steps of:
A. providing a blank of metal in a machine for metallic machining,
B. providing a threading tool in the machine, and
C. coordinating longitudinal and lateral feed of the tool with rotational movement of the blank about an axis of rotation such that the thread is cut into the blank, with both flanks of the end section having respective profiles that are different from profiles of corresponding flanks of the full thread section.
REFERENCES:
patent: 3645570 (1972-02-01), Johansson et al.
patent: 4332502 (1982-06-01), Wormald et al.
patent: 4625814 (1986-12-01), Helasuo et al.
patent: 4687368 (1987-08-01), Eklof et al.
patent: 4968068 (1990-11-01), Larsson
patent: 5730566 (1998-03-01), Goodwin et al.
patent: 5733137 (1998-03-01), Knoop
patent: 5791849 (1998-08-01), Goodwin et al.
patent: 6095266 (2000-08-01), Lundell
patent: 0 220 147 (1987-04-01), None
Liljebrand Per-Olof
Olsson Urban
Batson Victor
Burns Doane Swecker & Mathis L.L.P.
Sandvik AB
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