Note: Descriptions are shown in the official language in which they were submitted.
TITLE: IMPROVED BIT HOLDER FOR GRINDING APPARATUS
BACKGROUND
The present disclosure relates to improvements in
apparatus for grinding the hard metal inserts or working
tips of rock drill bits (percussive or rotary), tunnel
boring machine cutters (TBM) and raised bore machine
cutters (REM) and more specifically, but not exclusively,
for grinding the cutting teeth or buttons of a rock drill
bit or cutter.
In drilling operations the cutting teeth (buttons)
on the drill bits or cutters become flattened (worn) after
continued use. Regular maintenance of the drill bit or
cutter by regrinding (sharpening) the buttons to restore
them to substantially their original profile enhances the
bit/cutter life, speeds up drilling and reduces drilling
costs. Regrinding should be undertaken when the wear of the
buttons is optimally one third to a maximum of one-half the
button diameter.
Manufacturers have developed a range of different
manual and semi-automatic grinding machines including hand
held grinders, single arm and double arm self centering
grinding machines and grinders designed specifically for
mounting on drill rigs, service vehicles or set up in the
shop.
These types of machines utilize a grinding machine
having a spindle or rotor rotated at high speed. A grinding
cup or grinding pin, mounted on the end of the rotor or
spindle, grinds the button and typically the face of the
bit/cutter surrounding the base of the button to restore
the button to substantially its original profile for
effective drilling. In addition to the rotation of the
grinding cup, these types of grinding machines may include
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features where the grinding machine is mounted at an angle
to the longitudinal axis of the button and the grinding
machine is rotated to provide orbital motion with the
center of rotation lying in the center of the grinding cup.
When grinding the buttons, the centering aspects of the
grinding machine tend to center the grinding machine over
the highest point on the button.
Longstanding problems with these types of grinding
machines are vibration and noise due to high rotational
speeds, wear, the requirement for large compressors for
pneumatic systems and long grinding times per button, in
the larger sizes.
U.S. Patent No. 7,402,093 addressed a number of
problems with earlier machines and provided a grinding
machine carried on a support system where the grinding cup
is rotated at variable speeds preferably from about 2200 to
6000 RPM and the support system is capable of providing a
variable feed pressure preferably or optionally up to 350
kilos. In this type of machine there is a need to provide
better support for larger bits during grinding.
SUMMARY OF THE INVENTION
Accordingly the present disclosure provides
embodiments of a grinding apparatus for grinding the hard
metal inserts of rock drill bits. The grinding apparatus
has a grinding machine carried on a support system and
means for holding one or more bits to be ground. The
grinding machine is equipped with a grinding cup driven by
a motor to rotate about its longitudinal axis. An aspect of
the present disclosure relates to embodiments of grinding
apparatus wherein means for holding one or more rock drill
bits to be ground are provided that include a moveable
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floor plate for each aperature and movement of said floor
plate is controlled by a linear actuator.
Further features of the invention will be described
or will become apparent in the course of the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the disclosure may be more clearly
understood, the embodiments will now be described in detail
by way of example, with reference to the accompanying
drawings, in which:
FIGURE 1 is perspective view from the right side of one
embodiment of a grinding apparatus having a grinding
machine carried for vertical and horizontal adjustment by a
support system, and
means for holding the bit(s) to be
ground and with a schematic illustration of a large down
the hole bit (the bit illustration does not show the hard
metal inserts or buttons to be ground).
FIGURE 2 is left side view the grinding apparatus of FIGURE
1 with shielding removed around the bit.
FIGURE 3 is a top perspective view of one embodiment of bit
holder for the grinding apparatus of FIGURE 1.
FIGURE 4 is a bottom view of the bit holder of Figure 3
with the aperature closed.
FIGURE 5 is a bottom view of the bit holder of Figure 3
with the aperature open.
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FIGURE 6 is a top view of one embodiment of bit holder with
shelding removed according to the present invention.
FIGURE 7 is a front view of the bit holder of FIGURE 6.
FIGURE 8 is a rear bottom view of the bit holder of FIGURE
6.
FIGURE 9 an enlarged bottom view of the bit holder similar
to the one illustrated in FIGURE 6 with the motor for the
linear actuator arranged differently.
FIGURE 10 is an enlarged view of the motor for the linear
actuator of FIGURE 9.
DETAILED DESCRIPTION
With reference to the FIGURES 1 to 5 one embodiment
of a grinding apparatus is generally indicated at 1. The
grinding apparatus 1 includes a grinding machine 2, means
for holding one or more bits to be ground generally
indicated at 3 and a support system generally indicated at
4. The grinding machine 2, means for holding the bits 3 and
support system 4 are arranged to permit relative movement
between the grinding machine 2 and the bit to be ground to
permit alignment of the grinding machine 2 with the
longitudinal axis of the buttons on the bit. The grinding
apparatus 1 has a control system, part of which is
generally indicated at 5, having a programmable operator
control panel 35 capable of directly or indirectly
monitoring and adjusting one or more operational
parameters. The operational parameters may include feed
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pressure, grinding cup RPM, grinding time and other
parameters as noted herein.
In the embodiment of the grinding apparatus 1 shown
in Figures 1-5, the grinding machine 2 is carried by
support system 4 which includes an arm or lever system 6
journaled on a stand 7 attached to the rear 8 of an open
box 9. The bit holder means 3 consists of a table 10
mounted within the box 9.
In the embodiment shown, the arm or lever system 6
for carrying and positioning the grinding machine 2 as
noted previously is journaled onto a stand 7 at the rear 8
of the box 9. The arm system 6 consists of a first arm
section 11 having one end 12 journaled to the stand 7. The
other end 13 of the first arm section 11 is journaled to
the backside 14 of a first control box 15. The first arm
section 11, in this embodiment, controls the horizontal
location of the grinding machine 2 relative to the bit to
be reground. To the front side 16 of the first control box
is pivotally mounted a second arm section 17. The second
arm section 17 consists of a pair of parallel arms 18,19
with one end 20,21 of each arm 18,19 pivotally mounted to
the front side 16 of the first control box 15. The other
end 22,23 of each arm 18,19 is pivotally connected to the
backside 24 of a second control box 25. The second arm
section 17 controls the vertical movement of the grinding
machine 2 up and down.
In the embodiment illustrated in FIGURES 3-5, the
means for holding the bits 3 is a table 10 mounted within
the box 9 at pivot points on each side of the box 9 to
permit the table 10 to be tilted. In FIGURE 4 a linear
actuator 60 is shown as controlling the tilting action of
table 10. The bit holder means 3, in this case table 10,
may be provided with one or more apertures 50 to hold one
or more bits to be ground. In the embodiment illustrated
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table 10 has one aperture 50. When a bit(s) is positioned
in an aperture 50 the shank of the bit is placed against
the front edges 51,52 of aperture 50. The front edges 51,52
may be rubber coated. The bit is held in place against
front edges 51,52 by pressure plate 53 controlled by a
second linear actuator 54 and lever arm assembly 55. Means
are provided to monitor and control the travel of the
linear actuator. In the embodiment illustrated the linear
actuator 54 is an electro mechanical actuator. By
monitoring the amperage used by the electric motor for the
actuator 54, when the amperage spikes the control system 5
can stop the electric motor from advancing the actuator
further. The amperage will spike when the pressure plate 53
contacts the shank of the bit when the shank is contacting
front edges 51,52 of aperature 50. A shield 56 is attached
to and moves with the pressure plate 53 and fully covers
the opening between the rear 57 of pressure plate 53 and
back 58 of the aperture 50. The shield 56 prevents
accidental pinching of fingers, etc. when the pressure
plate 53 is retracted. The linear actuator 54 can be backed
off slightly to rotate the bit (to the next button to be
ground) within the aperture 50 without full retraction of
the linear actuator 54 and pressure plate 53. The controls
for operating the linear actuator 54 may be provided on the
sides of box 9. While the method of holding a bit in the
bit holder means is shown as a pressure plate 53 and linear
actuator 54 other arrangements are possible and the present
invention is not limited to the embodiment is illustrated.
FIGURES 6-10 illustate one embodiment of an
improvement to the bit holder shown in FIGURES 3-5. In
FIGURES 6-9 a moveable floor plate is illustrated on which
the free end of a drill bit can rest. The floor plate is
moveable to accommodate different sizes of drill bits
having longer or shorter stems. The floor plate positioning
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is controller by a linerar actuator. In the embodiments
illustrated the linear actuator is an electro-mechanical
actuator having a threaded rod as best shown in FIGURE 10
that is rotated using a gear assembly powered by an
electric motor. The moveable floor plate is mounted on a
bracket moveable up and/or down on vertical support member.
The threaded rod extends through a threaded block on the
bracket. As the threaded rod is rotated the bracket moves
up or down.
On advantage of the moveable floor plate of the
present invention is that after a button has been ground
the pressure plate holding the bit in position is backed
off slightly so that the bit can be rotated to position the
next button to be ground. The moveable floor plate supports
the bit without assistance from the operator.
Another advantage is that the floor plate can be
moved up or down so the bit is supported by pressure plate
near the working surface of the bit rather than down the
shank of the bit. This provides better support during
grinding.
Having illustrated and described a preferred
embodiment of the invention and certain possible
modifications thereto, it should be apparent to those of
ordinary skill in the art that the invention permits of
further modification in arrangement and detail and is not
restricted to the specific semi-automatic grinding
apparatus illustrated.
It will be appreciated that the above description
related to the preferred embodiment by way of example only.
Many variations on the invention will be obvious to those
knowledgeable in the field, and such obvious variations are
within the scope of the invention as described and claimed,
whether or not expressly described.
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