Boring or penetrating the earth – Bit or bit element – Specific or diverse material
Reexamination Certificate
1999-11-19
2001-04-24
Tsay, Frank S. (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Specific or diverse material
C175S431000
Reexamination Certificate
active
06220376
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to drilling, such as rock drilling, and relates in particular to a drill bit and a button for such drilling.
TECHNICAL BACKGROUND
Diamond enhanced buttons (DE-buttons) for percussive drilling and rotary drilling usually have semispherical, ballistical, conical or chisel shaped tips. The outer hard polycrystalline diamond layer (PCD-layer) is very thin, normally 0.2 mm and the service length of the button is directly related to how fast the PCD-layer is worn through. To get the most from the DE-buttons the DE-bits normally are designed to distribute the wear as evenly as possible, i.e. the gauge buttons that often are determining the service length are placed symmetrically and also the bit as a whole often has a more or less symmetrical shape, such as shown in Hedlund et al. U.S. Pat. No. 5,575,342. A way to increase the service length would be to increase the thickness of the PCD-layer. However, for technical and physical reasons it has not been possible to make the PCD-layer much thicker than 0.4 mm on semispherical buttons for percussive and rotary drilling.
DE-button bits are most useful when drilling in hard to extra hard abrasive rock where DE-button bits have the advantage that they do not need to be reground, while the wear on conventional cemented carbide-buttons is high, requiring regrinding several times.
U.S. Pat. No. 5,335,738 discloses a button of cemented carbide with a stud covered by a diamond layer. The PCD layer is thicker at certain parts of the button, for example at the tip point where a shallow hole in the substrate is provided and on the flank wherein a shallow groove around the semispherical tip is provided. The known button has a layer which provides less disadvantageous stresses and locally thicker PCD-layer. The service length of the known button has, in spite of these improvements, not been optimized. Dennis U.S. Pat. No. 5,379,854 discloses in one embodiment a button of cemented carbide with a diamond layer. The button surface has a sinusoidal cross section and an applied PCD-layer of similar contour. The ridges and the grooves of the sinusoidal contour of the cemented carbide button serve to prevent delamination of the PCD-layer and reduce the shear stresses in the bond zone between the PCD-layer and the cemented carbide. The sinusoidal profile of the PCD-layer provides several impact points which work simultaneously when the button is used for drilling.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a drill bit for percussive or rotary crushing rock drilling, wherein the service life of the bit is extended.
Another object of the present invention is to provide a button for a drill bit for percussive or rotary crushing rock drilling, wherein the service life of the button is extended.
Another object of the present invention is to provide a button and a drill bit for percussive or rotary crushing rock drilling, which provides for a faster penetration rate.
Still another object of the present invention is to provide a button for percussive or rotary crushing rock drilling, in which the geometry provides for beneficial displacement of the most active portion of the working end of the button.
SUMMARY OF THE INVENTION
These and other objects of the present invention have been attained by a drill bit which comprises a drill body having a connection section at a rear end thereof for connection to a drilling unit. The connection section defines a rotational center axis of the drill bit. The bit body further includes a plurality of buttons embedded in a front end of the drill body. Each button has a longitudinal center line. Each button comprises a cemented carbide body having a rear mounting portion embedded in the drill body, and a crushing end protruding from the drill body and being shaped symmetrically about the center line. Each button is oriented at a first acute angle of from about 35° to about 55° relative to the rotational center axis of the drill bit. The crushing end of each button comprises at least one annular groove arranged coaxially about the center line, whereby the crushing end includes local maximum points spaced apart by the groove. An imaginary line touching the maximum points defines a second acute angle relative to the center line of the button, the second acute angle being smaller than the first acute angle.
The invention also pertains to a button for a drill bit. The button comprises a cemented carbide body having a rear mounting portion defining a longitudinal center line, and a crushing end shaped symmetrically about the center line. The crushing end of the button comprises at least one annular groove arranged coaxially with the center line, whereby the crushing end includes local maximum points spaced axially apart by the groove. An imaginary line intersecting the maximum points defines an acute angle relative to the center line.
REFERENCES:
patent: 4109737 (1978-08-01), Bovenkerk
patent: 5335738 (1994-08-01), Waldenström et al.
patent: 5379854 (1995-01-01), Dennis
patent: 5575342 (1996-11-01), Hedlund et al.
patent: 6003623 (1999-12-01), Miess
patent: 6053263 (2000-04-01), Meiners
patent: 6135219 (2000-10-01), Scott
patent: 2180280 (1986-08-01), None
patent: 791-889 (1977-12-01), None
patent: 1344-888 (1986-01-01), None
Burns Doane Swecker & Mathis L.L.P.
Sandvik AB
Tsay Frank S.
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