Abrading – Abrading process – With critical nonabrading work treating
Patent
1997-08-11
1999-10-12
Rose, Robert A.
Abrading
Abrading process
With critical nonabrading work treating
451450, 451442, 451448, 451449, 451342, 451270, B24B 5502
Patent
active
059646497
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a grinding cup for grinding buttons of a rock drilling bit, said grinding cup including a shank that is rotatably mounted in a grinding machine and a wear part having a recess, said recess carrying out the grinding of the buttons. The invention also relates to a wear part for a grinding cup.
PRIOR ART BACKGROUND
When grinding cemented carbide buttons of a drill bit, a grinding cup of the type described above is normally used. The wear part of such grinding cup usually has an abrasive grinding surface that often includes granular diamond. However, the grinding of cemented carbide buttons generates both heat and abrasive cuttings to such an extent that it is necessary to cool the grinding cup and the button bit as well as to flush away the cuttings. The known prior art technique for such cooling is to supply cooling medium, normally water, through the grinding machine and axially through the grinding cup to provide the cooling medium to be discharged in the region where the wear part of the grinding cup engages the free end of the button.
It is previously known through for example International Publication WO 93/25346 to provide a first flush channel which extends centrally through the shank of the grinding cup and which connects to a second flush channel, terminating centrally in a recess in the wear part of the grinding cup.
That recess cannot perform a grinding function and thus leaves a projection in the center of a ground button. The projection may constitute a starting point for a crack in the button when the rock drill bit is reused and thus it may shorten the length of life of the drill bit.
Furthermore it is previously known to provide a groove extending diametrically over the center of the recess, to spread the flushing medium and whereby the available volume of abrasive material is undesirably decreased.
OBJECTS AND SUMMARY OF THE PRESENT INVENTION
An object of the present invention is to provide a grinding cup for grinding of rock drill bit buttons, configured such that the active surface of the button becomes smooth after grinding and such that cools the button sufficiently. Furthermore the configuration of the grinding cup according to the present invention makes it possible to increase the volume of abrasive material in the wear part of the grinding cup. The objects of the present invention are realized by a wear part that has a flush channel which is spaced from a center axis of the wear part.
DESCRIPTION OF THE DRAWINGS
Below embodiments of a grinding cup according to the present invention will be described, reference being made to the accompanying drawings, where FIG. 1 shows a partly sectioned side view of a grinding cup according to the present invention; FIG. 2 shows an end view of the grinding cup shown in FIG. 1; FIGS. 3 and 4 show partly sectioned side views of alternative embodiments of a grinding cup according to the present invention; and FIGS. 5 to 7 show end views of alternative grinding cups according to the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
The grinding cup 10 according to primarily FIGS. 1 and 2 includes a shank 11, a wear part 12 and an intermediate portion 13 that bridges the shank 11 and the wear part 12. Preferably the shank 11 and the intermediate portion 13 are in one piece and form a carrier for the wear part 12. The wear part 12 is connected to the intermediate portion 13 in a suitable way, preferably by brazing. The grinding cup 10 is rotatable about to longitudinal centre axis 14.
The free end of the wear part 12 has a cavity 15 in the shape of a segment of a sphere when the button 16, to be grinded, has a hemispherical free end. The button is preferably made of cemented carbide. However, if the buttons have ballistic or conical free ends then the cavity of course has a complementary shape. The cavity 15 is intended to engage and cooperate with the free end of a button that is subjected to grinding. The cavity is equipped with an abrasive material, preferably diamond. The other parts
REFERENCES:
patent: 4102084 (1978-07-01), Bloomquist
patent: 4802799 (1989-02-01), Rachev
patent: 5070654 (1991-12-01), Manqvist et al.
patent: 5634747 (1997-06-01), Tukala et al.
patent: 5637037 (1997-06-01), Bergquist
Bergqvist Arne
Nava Peter
Nguyen George
Rose Robert A.
Sandvik AB
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