U.S. patent application number 10/283150 was filed with the patent office on 2003-03-20 for grinding tool for grinding buttons of a rock drill bit, a grinding spindle and method for mounting the grinding cup on a grinding spindle.
Invention is credited to Bergquist, Arne, Lindgren, Goran.
Application Number | 20030054745 10/283150 |
Document ID | / |
Family ID | 20414431 |
Filed Date | 2003-03-20 |
United States Patent
Application |
20030054745 |
Kind Code |
A1 |
Bergquist, Arne ; et
al. |
March 20, 2003 |
Grinding tool for grinding buttons of a rock drill bit, a grinding
spindle and method for mounting the grinding cup on a grinding
spindle
Abstract
A grinding tool for grinding buttons of a rock drill bit
includes a spindle having a longitudinal axis of rotation, and a
grinding cup mounted on the spindle by a tongue-and-socket
connection. A fastener in the form of a coil spring secures the
grinding cup to the spindle. The grinding cup can be inserted into
the inside of, or around the exterior of, the coil spring. When the
spindle is rotated in a working direction, the spring tightens
against the grinding cup. To install or remove the grinding cup,
the grinding cup is rotated relative to the spindle in a direction
corresponding to the working direction, whereby engagement between
the grinding cup and the coil spring becomes loosened.
Inventors: |
Bergquist, Arne; (Sandviken,
SE) ; Lindgren, Goran; (Gavle, SE) |
Correspondence
Address: |
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
20414431 |
Appl. No.: |
10/283150 |
Filed: |
October 30, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10283150 |
Oct 30, 2002 |
|
|
|
09453880 |
Feb 11, 2000 |
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Current U.S.
Class: |
451/540 ;
451/548 |
Current CPC
Class: |
B24D 7/10 20130101; B24B
45/00 20130101; B24B 3/33 20130101 |
Class at
Publication: |
451/540 ;
451/548 |
International
Class: |
B24B 033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 1999 |
SE |
9900458-2 |
Claims
What is claimed is:
1. A grinding tool for grinding buttons of a rock drill bit
comprising: a spindle having a longitudinal axis of rotation; a
grinding cup mounted on the spindle by a tongue-and-socket
connection which includes a cylindrical surface disposed on the
grinding cup, the cylindrical surface being symmetrical with
respect to the axis; a vibration damper disposed between the
grinding cup and the spindle; a fastener for securing the grinding
cup to the spindle, the fastener being attached to the spindle
against axial displacement relative thereto, the fastener arranged
to engage the cylindrical surface of the grinding cup to rotate the
grinding cup when the spindle is rotated in a working direction,
the fastener arranged to tighten a grip on the grinding cup when
the spindle is rotated in the working direction during a grinding
operation, and to permit rotation of the grinding head relative to
the spindle in a direction corresponding to the working direction
to loosen the grinding head for insertion and removal thereof.
2. The grinding tool according to claim 1 wherein the fastener
comprises a coil spring.
3. The grinding tool according to claim 2 wherein the coil spring
defines a sole means of transferring rotation from the spindle to
the grinding head.
4. The grinding tool according to claim 3 wherein one end of the
spring is secured against axial movement and rotational movement
relative to the spindle.
5. The grinding tool according to claim 3 wherein the spring is
situated inside of the cylindrical surface.
6. The grinding tool according to claim 3 wherein the spring is
situated outside of the cylindrical surface.
7. A grinding cup for grinding buttons of a rock drill bit, the
grinding cup having a body defining an axis of rotation and
including a forward wear part and a rear shank, a flush channel
extending through the shank, the shank including a cylindrical
surface arranged symmetrically relative to the axis and defining a
sole means of receiving a rotary drive torque during a grinding
operation.
8. The grinding cup according to claim 7 wherein the body further
comprises an intermediate portion which connects the shank to the
wear part, the wear part including flush channels oriented
eccentrically relative to the axis and communicating with the flush
channel that extends through the shank.
9. Apparatus for holding an insert-grinding cup, comprising a
grinding spindle defining an axis of rotation and including a
cylindrical surface at one end thereof adapted to receive a
grinding cup, and a fastener for securing a grinding cup, the
fastener disposed against the cylindrical surface and attached
against axial movement relative to the spindle, the fastener
arranged to permit movement of a grinding cup relative to the
spindle in a direction corresponding to a working direction of the
spindle.
10. The apparatus according to claim 9 wherein the fastener
comprises a coil spring which constitutes a sole means of
transferring rotation from the spindle to a grinding cup.
11. The apparatus according to claim 10 wherein the cylindrical
surface comprises an inner surface of a recess formed in the
spindle, the recess adapted to receive the coil spring and a
grinding cup, the spring being radially contractible to hold a
grinding cup.
12. The apparatus according to claim 10 wherein the cylindrical
surface comprises an outer surface of a projection of the spindle,
the projection adapted to receive the coil spring and a grinding
cup, the spring being radially expandible to hold a grinding
cup.
13. The apparatus according to claim 10 wherein one axial end of
the spring is secured to the spindle against rotation and axial
movement relative thereto, and an opposite axial end of the spring
is free.
14. A method for mounting a grinding cup on a grinding spindle for
grinding buttons of a rock drill bit, the grinding spindle
including a first cylindrical surface, the grinding cup including a
forward wear part and a rear shank having a second cylindrical
surface connectable to the first cylindrical surface, and a coil
spring fastener for interconnecting the first and second
cylindrical surfaces, the method comprising the steps of: A)
attaching the coil spring fastener to the grinding spindle such
that the fastener is immovable relative thereto in the axial
direction; B) positioning a vibration-damping element between the
spindle and the grinding cup; and C) moving the grinding cup
axially into engagement with the spindle while rotating the
grinding cup relative to the spindle in a direction corresponding
to a working direction of the spindle to elastically loosen the
coil spring fastener and permit the grinding cup to be axially
inserted onto the spindle.
15. The method according to claim 14 wherein step A is performed
prior to step B.
16. The method according to claim 14 wherein step B is performed
prior to step A.
Description
TECHNICAL FIELD
[0001] The present invention relates to a grinding tool for
grinding buttons of a rock drill bit, a grinding cup, a grinding
spindle and a method for mounting the grinding cup on a grinding
spindle.
PRIOR ART
[0002] A conventional grinding tool includes a grinding cup
fastened to a rotary spindle, there being a vibration damping
device between the spindle and grinding cup.
[0003] When grinding cemented carbide buttons of a drill bit, a
grinding cup is normally used. The wear part of such grinding cup
usually has an abrasive grinding surface that often comprises
diamond particles. 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. A prior art means for cooling involves
supplying cooling medium, normally water, through the grinding
machine and axially through the grinding cup to discharge the
cooling medium in the region where the wear part of the grinding
cup engages the free end of the button, as is shown in U.S. Pat.
No. 5,964,649.
[0004] Through for example U.S. Pat. No. 5,688,163, there is
previously known a tool for grinding buttons of a rock drill bit.
The tool is secured to a grinding head, wherein the rotatably
journalled spindle carries a grinding cup. The grinding cup is
vibration-damped by means of a bushing of rubber for minimizing the
risk for white fingers. Furthermore, the prior art grinding tool
comprises means for quickly mounting and dismounting the grinding
cup on and from the grinding spindle. Said means comprises an
external, movable sleeve, a spring, a ball in a radial hole in the
spindle, an O-ring and driving surfaces. This complicates the
design of the grinding tool and requires two hands for demounting
of the grinding cup.
[0005] Through for example U.S. Pat. No. 5,727,994 there is
previously known a tool for grinding buttons of a rock drill bit.
Also this grinding tool comprises means for quickly mounting and
dismounting the grinding cup on and from the grinding spindle. Said
means comprises an O-ring that co-operates with a cylindrical
surface and polygonal co-operative surfaces for driving. In case a
flush medium is supplied to the grinding cup without the grinding
cup abutting against a button being ground, the pressure can
influence the grinding cup from the inside which over-powers the
frictional force between the O-ring and the grinding cup. Thus the
grinding cup will become dislodged from the grinding spindle. In
addition some skill is needed for aligning the driving surfaces
when mounting the grinding cup.
OBJECTS AND SUMMARY OF THE INVENTION
[0006] One object of the present invention is to provide a grinding
tool for grinding drill bit buttons, which realizes the advantages
of the prior art,
[0007] Another object of the present invention is to provide a
grinding tool that can be mounted or dismantled quickly.
[0008] Another object of the present invention is to provide a
grinding tool that comprises a minimum of parts.
[0009] Another object of the present invention is to provide a
grinding tool, which can be mounted or dismounted by means of one
hand only.
[0010] Another object of the present invention is to provide a
grinding tool which is developed such that the grinding cup is
retained harder as more torque is applied.
[0011] The objects of the present invention are realized by a
grinding tool for grinding buttons of a rock drill bit, a grinding
cup, a spindle and a method of mounting the grinding cup on a
spindle. The grinding tool comprises a spindle having a
longitudinal axis of rotation, and a grinding cup mounted on the
spindle by a tongue-and-socket connection which includes a
cylindrical surface disposed on the grinding cup, the surface being
symmetrical with respect to the axis. A vibration damper is
disposed between the grinding cup and the spindle. A fastener
secures the grinding cup to the spindle. The fastener is attached
to the spindle against axial displacement relative thereto. The
fastener is arranged to engage the cylindrical surface of the
grinding cup to rotate the grinding cup when the spindle is rotated
in a working direction. The fastener is arranged to tighten a grip
on the grinding cup when the spindle is rotated in the working
direction during a grinding operation, and to permit rotation of
the grinding head relative to the spindle in the working direction
to loosen a grinding head for insertion and removal thereof.
[0012] In another aspect of the invention the grinding cup has a
body defining an axis of rotation and includes a forward wear part
and a rear shank. A flush channel extends through the shank. The
shank includes a cylindrical surface arranged symmetrically
relative to the axis and defining a sole means of receiving a
rotary drive torque during a grinding operation.
[0013] In another aspect of the invention an apparatus is provided
for holding an insert-grinding cup. The apparatus comprises a
grinding spindle which defines an axis of rotation and includes a
cylindrical surface at one end thereof adapted to receive a
grinding cup. The apparatus also includes a fastener for securing a
grinding cup. The fastener is disposed against the cylindrical
surface and is attached against axial movement relative to the
spindle. The fastener is arranged to permit movement of a grinding
cup relative to the spindle in a direction corresponding to a
working direction of the spindle.
[0014] The invention also pertains a method for mounting a grinding
cup on a grinding spindle for grinding buttons of a rock drill bit.
The grinding spindle includes a first cylindrical surface. The
grinding cup includes a forward wear part and a rear shank having a
second cylindrical surface connectable to the first cylindrical
surface. A coil spring fastener is provided for interconnecting the
first and second cylindrical surfaces. The method comprises the
steps of:
[0015] A. attaching the coil spring fastener to the grinding
spindle such that the fastener is immovable relative thereto in the
axial direction;
[0016] B. positioning a vibration-damping element between the
spindle and the grinding cup; and
[0017] C. moving the grinding cup axially into engagement with the
spindle while rotating the grinding cup relative to the spindle in
a direction corresponding to a working direction of the spindle to
elastically loosen the coil spring fastener and permit the grinding
cup to be axially inserted onto the spindle,
[0018] wherein step A can be performed prior to, or after, step
B.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Below, three embodiments of a grinding cup according to the
present invention will be described, reference being made to the
accompanying drawings:
[0020] FIG. 1A shows an exploded cross-sectional view of an end of
a grinding tool according to the present invention;
[0021] FIG. 1B shows the grinding tool of FIG. 1A in a mounted
position;
[0022] FIG. 1C shows the grinding tool in FIG. 1B mounted to a
flushing head;
[0023] FIGS. 1D-1F show the grinding cup according to FIG. 1A in an
end view, in a cross-section (section 1E-1E in FIG. 1D) and in an
opposite top view, respectively;
[0024] FIGS. 1G-1I show a spring in an end view, in a side view and
in an opposite top view, respectively;
[0025] FIG. 1J shows the end of the grinding tool according to FIG.
1B in magnification;
[0026] FIG. 2A shows an exploded cross-sectional view of an end of
a grinding tool according to the present invention in an
alternative embodiment;
[0027] FIG. 2B shows the grinding tool in FIG. 2A in a mounted
position;
[0028] FIGS. 2C-2E show the grinding cup according to FIG. 2A in an
end view, in a cross-section and in an opposite top view,
respectively;
[0029] FIG. 3A shows an exploded cross-sectional view of an end of
a grinding tool according to the present invention in an
alternative embodiment;
[0030] FIG. 3B shows the grinding tool in FIG. 3A in a mounted
position; and
[0031] FIGS. 3C-3E show the grinding cup according to FIG. 3A in an
end view, in a cross-section and in an opposite top view,
respectively.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0032] A first embodiment of a grinding tool 10 according to the
present invention for grinding buttons of a rock drill bit is
described hereinafter with reference to FIGS. 1A-1J. The tool
comprises a grinding spindle 11, a vibration-damping means 13, a
mounting means or a spring 14 and a grinding cup 15. In FIG. 1C the
tool 10 is shown as mounted to a swivel or flushing head 12 to form
a grinding assembly.
[0033] The upper end of the grinding spindle 11 is intended to be
rotatably mounted in a grinding head, not shown, of the type shown
and described in EP-B-734,306, which hereby is incorporated by
reference into the description. The grinding head is thus connected
to a power source such as an electric motor and can be vertically
displaced, i.e. downwardly and upwardly. The grinding head
comprises an external housing (not shown) which is stationary. The
grinding spindle 11 is rotatably journalled in a boring of the
spindle house by means of roller bearings that are spaced apart
axially in the longitudinal direction of the grinding spindle. The
end of the grinding spindle that projects from the external housing
carries the flushing head 12. The flushing head 12 is provided with
one or several openings 12a which are intended to receive hoses
that conduct flush medium from a suitable source. The connection of
the hoses to the source prevents a part of the flushing head from
rotating when the grinding spindle 11 is rotated. The flushing head
12 comprises two sealing sleeves 12b that surround the grinding
spindle 11. The grinding spindle is intended to perform a wobbling
movement relative to the buttons during grinding. The forward end
of the grinding spindle comprises a central cylindrical recess 27
in which a central flush channel 28 terminates. The recess 27 is
substantially symmetrical about the rotational axis 20 and
comprises a cylindrical wall 29 and a bottom surface 30. The recess
27 has a diameter D4. The bottom surface 30 is substantially planar
and perpendicular to the axis 20. A radially extending hole 32
extends through the wall 30 and intersects the jacket surface 31 of
the spindle. An axial groove 33 extends from the hole axially
forwards along the wall 29 and forwards to the free end surface 34
of the spindle 11. The spindle may eventually include a
circumferential groove in the surface 29 to receive an O-ring for
radial vibrational damping, depicted at right in FIG. 1J.
[0034] The vibration-damping means comprises a circular washer 13
made of plastics or rubber. The washer has two plane-parallel side
faces and a central hole. The spring 14, which is primarily shown
in FIGS. 1G-1I, is a helical coil spring made from a tightly wound,
preferably stainless steel wire of about 1 mm diameter. The spring
14 has, in the shown embodiment, about 4.5 left-wound turns and its
ends 35, 36 have mutually different appearances. One end 35 lies
within an imaginary cylindrical tube, which is formed by the
spring, while its other end 36 projects outside of said tube,
perpendicularly to the axis 20. The spring shall, as seen from the
other end 36, be wound opposed to the direction R in which the
spindle will rotate during grinding. The spring has an inner
diameter D5, for example 11 mm, and an external diameter D6.
[0035] The grinding cup 15 according to the present invention, see
primarily FIGS. 1D-1F, comprises a shank 16, a wear part 17, and
first and second intermediate portions 18, 19 which connect the
shank 16 to the wear part 17. The shank and the recess 27 together
define a tongue-and-socket connection between the grinding cup 15
and the spindle 11. All segments 16-19 are cylindrical without
having any driving grooves and have a substantially similar axial
extension. Preferably, the shank 16 and the intermediate portions
18, 19 are made as a one-piece unit. The shank 16 comprises a
cylindrical shank surface 37 which preferably via an entering bevel
connects to a planar rear surface 23, which is substantially
perpendicular to the axis 20 and which is intersected by a
preferably central flush channel 24. The wear part 17 is connected
to the first intermediate portion 18 in a suitable manner,
preferably by direct sintering or by brazing via conical surfaces,
which facilitates the jointing method. Within the scope of the
present invention it is also possible for the wear part 17 to be
made as a one-piece unit with the first intermediate portion 18.
The grinding cup 15 is symmetrical relative to its longitudinal
central or rotational axis 20, and therefore the cup may be used
both for right-hand and left-hand grinding.
[0036] The shank 16 has a diameter D1; the second intermediate
portion 19 has a diameter D2; and the first intermediate portion 18
and the wear part 17 have a diameter D3. The diameters fulfill the
following condition:
[0037] D2<D1<D3. Alternatively D3 can be less than D2. A
shoulder 21 is formed at a transition between the shank 16 and the
second intermediate portion 19. The shoulder 21 is planar and
substantially perpendicular to the axis 20.
[0038] The forward end of the wear part 15 has a recess 22 in the
shape of a ballistic segment when the buttons have ballistic free
ends. However, if the buttons have conical or spherical free ends
then the recess of course has a corresponding shape. The recess 22
is intended to be in engagement with, and cooperate with, the free
end of the button being ground. The button is frequently made from
hard metal, and the recess 22 is therefore provided with an
abrasive material, preferably diamonds in a binder matrix. If the
wear part 15 is of one piece with the first intermediate portion
18, i.e., if the wear part blank is made of steel, it can be
suitable-by electroplating or in some other suitable manner, to
apply a diamond layer to the wear part blank.
[0039] The wear part 15 has two flush channels 25, 26 extending
axially parallel with and spaced from the axis 20. Each flush
channel 25, 26 extends axially forwardly from the rear side of the
wear part, and terminates at least in the recess. Preferably, the
channel 25, 26 also terminates at a portion radially outside of the
recess 22. Each channel 25, 26 has a rectangular basic cross
sectional shape, the short sides of which are substantially
parallel with the central axis 20 and the long sides of which are
parallel to each other. An imaginary extension line of one long
side of each channel does not intersect the opposite channel, i.e.,
the channels are not diametrically aligned with one another. The
radially inner end of each channel is radially spaced from the
central axis. Through this design of the grinding cup, the buttons
can be ground without leaving a "wart" or projection on the top of
the button, which diminishes the risk for the button breaking
prematurely during drilling. In addition, a constant flow of flush
medium is obtained, since the channels 25, 26 can not be clogged by
grinding residues during the grinding process.
[0040] The described grinding tool 10 functions in the following
manner with reference primarily to FIG. 1J, wherein it is
understood that the grinding spindle 11 and the swivel 12 already
have been assembled to each other and to the grinding head. The
washer 13 is pushed into the recess 27 of the spindle such that it
abuts against the bottom surface 30 of the recess. Then the spring
14 is pushed into the recess such that the end 35 of the spring
first enters and then the other end 36 of the spring is elastically
pushed radially inwards for entering the groove 33. The groove
guides the end 36 such that it will rebound (snap) into the hole 32
after further transport of the spring into the recess. Through
co-operation between the end 36 and the hole 32, both the washer
and the spring are secured from falling out from the recess.
[0041] The outer diameter D6 of the spring is dimensioned somewhat
less than the diameter D4 of the recess 27. Then the grinding cup
is aligned with the axis 20 such that the shank 16, with a diameter
for example of 11.5 mm, can be inserted towards the spring 14.
About simultaneously as the free end of the shank abuts against the
axially forward part of the spring also the second intermediate
portion 19 of the cup engages the wall 29 of the recess. That is,
the diameter D1 is about the same as the diameter D4 to achieve a
slide fit. By further pushing the grinding cup inwardly, the shank
will enter the spring and, due to the difference in diameter of
about 0.5 mm between D2 and D5, the spring is adapted to the
diameter of the shank and therefore the grinding cup can be pushed
into the recess until the end surface 23 of the cup abuts against
the bottom surface 30. In that position there is always a gap G
between the end surface 34 and the grinding cup such that
vibrations shall be extinct in the washer.
[0042] To further facilitate the mounting and to diminish the
strain on the spring, the cup is rotated, at least less than a half
turn, during insertion of the shank into the spring. The cup is
then rotated in a direction opposite the winding of the spring for
increasing the diameter D5 of the spring and the insertion becomes
easy. If the cup is rotated in the same direction as the windings
of the spring, the spring will squeeze the shank such that
insertion cannot be done. This phenomena is completely dependent on
one end of the spring being free and the other end being secured
from rotation such that the friction between the spring and the
shank increases or diminishes depending on the rotational
direction. The phenomenon is then used for driving the grinding cup
during grinding. The direction of winding of the spring decides in
which direction the tool drives the grinding cup. Although the
embodiment shows a left-wound screw spring, right-wound springs
will be frequently used.
[0043] By axially securing the axial forward end 36 of the spring
in the hole 32, plastic deformation of the spring is counteracted
during loosening of the cup, since the pitch can not be increased
due to the thread windings in the spring abutting against each
other at pure retraction without rotating the grinding cup. The
grinding cup is then adjusted in a position relative to the button
which is to be ground, that is in a position where the wear part 17
is in engagement with the button 38, FIG. 1C. The grinding cup 15
is then rotated in the working direction R to perform grinding of
the button. The friction between the shank 16 and the spring is
increased by acceleration of the spindle. By flushing through the
grinding tool, the cup 10 cannot disengage in spite of the lack of
axial support from the button because the spring will be somewhat
tilted in the recess 27 and thereby wedge up the shank. At provoked
tests with the spring soaked with oil or soap, the cup has not been
able to be drawn loose without the aid of the above described
relative rotation. The grinding cup can be mounted and dismounted
with only one hand.
[0044] During loosening of the grinding cup, the procedure for
mounting is substantially reversed except that the cup is
relative-rotated in the same direction as when being mounted. The
spring and the washer will remain in the recess until they have
been worn and must be exchanged.
[0045] FIGS. 2A-2F, show an alternative embodiment of a grinding
tool 10' according to the present invention with indexed reference
numerals in accordance with the above-captioned embodiment. This
embodiment differs from the above-described embodiment foremost in
that the grinding cup 15' is guided via conical cooperating
surfaces on the clip, the washer 13' and the grinding spindle 11'.
The washer 13' minimizes the transfer of vibrations from the
grinding cup to the grinding spindle in connection with the
grinding of the drill bit button, and it efficiently seals such
that abrasive material does not enter into the recess.
[0046] The spring becomes expanded in the two previously described
embodiments of FIGS. 1A-1I and 2A-2E for holding the grinding cup,
while the spring in the next embodiment (FIGS. 3A-3E) functions by
contraction for holding the grinding cup.
[0047] That is, FIGS. 3A-3E show an alternative embodiment of a
grinding tool 10" according to the present invention. This
embodiment differs from the above-described first embodiment of
FIGS. 1A-1I foremost in that the shank 16' of the grinding cup 15'
comprises a central recess 37' intended to receive both the washer
13' and the projecting free end of the grinding spindle 11'. Said
free end or projection carries the spring 14', the axial forward
end 36' of which faces radially inwardly for co-operation with a
hole 32' in the spindle 11'. The embodiment is primarily intended
for grinding smaller buttons where the space around the hard metal
button is limited by adjacent buttons, wherein the coupling between
the cup and the spindle can be arranged regardless of the dimension
of the grinding end.
[0048] Thus, the present invention relates to a grinding tool for
grinding buttons of a rock drill bit, a grinding cup, a spindle and
a method for mounting the grinding cup on a spindle, wherein a
plurality of advantages in relation to prior art can be mentioned.
For example, the grinding tool can be mounted or dismounted quickly
with a minimum of parts and with a few simple manual operations;
the tool can be mounted or be dismounted with only one hand; and
the tool is made such that the grinding cup shank is held more
firmly as larger torque is applied onto the grinding cup.
* * * * *