Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED GRINDING APPARATUS
BACKGROUND OF THE INVENTION
The present invention relates to improvements
in apparatus for grinding the hard metal inserts or
working tips of drill bits (percussive or rotary),
tunnel boring machine cutters (TBM) and raised bore
machine cutters (RBM) and more specifically, but not
exclusively, for grinding the tungsten carbide cutting
teeth or buttons of a 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 machines for setting up two or more bits
to be ground, mobile machines for grinding on the road
or in a workshop and grinders designed specifically for
mounting on drill rigs, service vehicles or set up in
the shop. The present invention is particularly.
applicable to mobile grinding apparatus of the type
described in U.S. Patent No. 5,193,312 and semi-
automatic grinding machines as described in U.S. Patent
No. 5,070,654.
These types of machines utilize a grinding cup
having the desired profile rotated at high speed to
grind the carbide button and the face of the bit/cutter
surrounding the base of the button to restore the button
to substantially its original profile for effective
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drilling. When grinding buttons, the centering aspects
of the grinding machine tend to center the grinding
machine over the highest point on the button. On buttons
where wear is uneven, typically gauge buttons, this may
result in regrinding the button off center from its
longitudinal axis.
The conventional grinder designs switch
between grinding pressure and balance pressure to
achieve the desired effect. This, for example, does not
allow for a grinding pressure equal to zero. In
conventional grinder designs, the minimum grinding
pressure is equivalent to the weight of the arm or lever
section and the components attached to it. This may, for
example, result in grinding pressure that is too great
in relation to what is optimum for the size, type and
profile of the button being sharpened.
The gauge buttons are mounted in the bit at an
angle relative to the face of the bit. In order to
properly regrind a worn gauge button the bit must be
tilted to correspond to the angle at which the gauge
buttons are mounted in the bit. In order to regrind all
the buttons on the bit, the operator must continually,
tilt and rotate the bit as he proceeds from button to
button and/or bit to bit.
SUMMARY OF THE INVENTION
It is an object of the present invention to
provide means to help align, and optionally lock, the
grinding machine with the longitudinal axis of the
button to be ground.
It~ is a further object of the present
invention to provide a biased side load to the grinding
machine to help align the grinding machine with the
longitudinal axis of the button to be ground.
It is a further object of the present
invention to. provide a balance pressure to the arm
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section which controls the movement of the grinding
machine along the longitudinal axis of the bit or button
when not in use and grinding. pressure when in use.
It is a further object of the present
invention to provide a controlled combination of balance
pressure and grinding pressure to the grinding machine,
whenever necessary.
It is a further object of the present
invention to minimize operator set up and movement of
the bit during regrinding.
Accordingly the present invention provides a
grinding apparatus for grinding the hard metal inserts
or working tips of drill bits (percussive or rotary),
tunnel boring machine cutters (TBM) and raised bore
machine cutters (RBM). The grinding apparatus consists
of a means for holding one or more bits to be ground. In
the preferred embodiment the means to hold the bits) is
a table mounted in or on a frame, box or stand and is
provided with one or more apertures to hold one or more
bits to be ground. A grinding machine is carried by an
arm or lever system that permits movement of the
grinding machine relative to the bit or button to be
ground. This is normally horizontal and vertical
movement. Means are provided to help align .the grinding
machine with the longitudinal axis of the button to be
ground. In one embodiment the means to help align the
grinding machine with the longitudinal axis of the
button provides a biased side load, optionally
adjustable, to the grinding machine.
Another aspect of the present invention
relates to means to provide a balance pressure to the
arm or lever section that controls the movement of the
grinding machine in the direction of the longitudinal
axis of the button or bit when not in use and grinding
pressure when in use.
Another aspect of the present invention
relates to means to provide a controlled combination of
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balance pressure and grinding pressure to the grinding
machine. This allows for a greater range of grinding
pressure, or reduction of minimum grinding pressure by
countering the combined weighty of the arm or lever
section and all other components contributing to feed
during grinding.
Another aspect of the present invention
relates to a grinding apparatus for grinding the hard
metal inserts or working tips of drill bits (percussive
or rotary), tunnel boring machine cutters (TBM) and
raised bore machine cutters (RBM). The grinding
apparatus includes a means for holding one or more bits
to be ground. The means for holding the bits) is
tiltably or pivotably mounted in or on a frame, box or
stand with means to control the tilting/pivoting action.
The means for holding the bits) is preferably a table
provided with one or more apertures to hold one or more
bits to be ground. A grinding machine is carried by an
arm or lever system that permits horizontal and vertical
movement of the grinding machine relative to the bit or
button to be ground.
A further aspect of the present invention
relates, where the grinding machine uses a hex drive
configuration as described in U.S. Patent No. 5,639,273
and U.S. Patent No. 5,727,994, to a means to easily
align and attach the grinding cup and detach the
grinding cup after use.
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 invention may be more
clearly understood, the preferred embodiments thereof
will now be described in detail by way of example, with
reference to the accompanying drawings, in which:
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FIGURE 1 is a perspective view of one embodiment of an
improved grinding apparatus according to the
present invention having a grinding machine
5 carried for vertical and horizontal
adjustment by an arm or lever system
journaled on a stand and with a tiltable
table, pivotally mounted in a box, for
holding the bits) to be ground;
FIGURE 2 is a top plan view of the box and tilting
table of the grinding apparatus of FIGURE 1;
FIGURE 3 is a top plan view, partially cut away, of the
apertures for holding the bits in the table
of Figure 2;
FTGURE 4 is a plan view of the left side of the
grinding apparatus of FIGURE 1 showing the
means of tilting the table;
FIGURE 5 is a plan view of the right side of the
grinding apparatus of FIGURE 1;
FTGURE 6 is a plan view of the left side of a first
arm 'section of the arm system of FIGURE 1;
FIGURE 7 is a top plan view, partly broken away, of the
first arm section of FIGURE 6;
FIGURE 8 is a close-up plan view of one end of the
first arm section of FIGURE 6;
FIGURE 9 is a side view in cross section of a first
control box and second arm section for setting
the balance pressure and feed pressure for the
grinding machine of FIGURE 1;
FIGURE 10 is a front plan view of the grinding machine
and second control box of the arm system of
FIGURE 1:
FIGURE 11 is an enlarged side view, partially in cross
section, of the second control box of FIGURE
10;
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FIGURE 12 is a front plan view of another embodiment of
an improved grinding apparatus according to
the present invention having a grinding
machine carried for vertical and horizontal
adjustment by an arm or lever system journaled
on a stand or frame and with a tiltable table
for holding the bits) to be ground;
FIGURE 13 is a front plan view of the frame for the
grinding apparatus of FIGURE 12.
FIGURE 14 is a left side plan view of the frame of
FIGURE 12;
FIGURE 15 is a right side view of the frame of FIGURE
13;
FIGURE 16 is a front plan view of the arm or lever
system of FIGURE 12;
FIGURE 17 is a top plan view of the arm or lever system
of FIGURE 16;
FIGURE 18 is a top plan view of the tiltable table for
holding the bits to be ground of the grinding
apparatus of FIGURE 12;
FIGURE 19 is a right side plan view of the table of
FIGURE 18; and
FIGURE 20 is a plan view of bottom of the frame of
FIGURE 13.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to the Figures 1 to 11 one
embodiment of a grinding apparatus according to the
present invention is generally indicated at 1. The
grinding apparatus 1 includes means for holding one or
more bits to be ground generally indicated at 2. In this
embodiment the means for holding the bits) consists of
an open box 3 having a table 4 mounted within the box. A
grinding machine 5 is carried by an arm or lever system,
generally indicated at 6, journaled on a stand 7
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attached to the rear 8 of box 3. A compressed air feed
is provided to operate various aspects of the grinding
apparatus as discussed in detail below.
In order to minimize operator set up and
movement of the bit during regrinding, table 4 is
tiltably mounted within box 3 at pivot points 9,10 on
each side 11, 12 of the box 3 (see Figures 4 and 5). The
table 4 is provided with one or more apertures l3 to
hold one or more bits to be ground. rn7hen a bit (s) (not
shown) is positioned in aperture 13 the bit is held in
place by pressure plate 14 controlled by a locking
cylinder 15. A shield 16 is attached to and moves with
the pressure plate 14 and fully covers the opening
between the rear of pressure plate 14 and back 17 of
aperture 13. The shield 16 protects the piston rod of
the cylinder 15 and prevents accidental pinching of
fingers, etc. when the locking cylinder and pressure
plate are retracted. The locking cylinder 15 can be
depressurized and backed off slightly to rotate the bit
(to the next button to be ground) within the aperture 13
without full retraction of the locking cylinder 15 and
pressure plate 14 attached to it.
If the button to be ground is a gauge button,
it is typically mounted in the bit at an angle relative
to the face of the bit. The grinding machine 5, in order
to properly regrind a worn button, should be aligned
with the longitudinal axis of the button. Accordingly to
regrind the gauge buttons, in the embodiment shown,
table 4 is tilted to correspond to the angle at which
the gauge buttons are mounted in the bit. Alternatively,
the grinding apparatus could have, for example, a
tilting feature or positioning feature allowing the
grinding machine to be aligned with, and provide balance
and grinding pressure along, the longitudinal axis of
the button, without tilting the bit or button.
The means of tilting table 4 is best
illustrated with reference to Figure 4. An arced slot 20
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is provided in the side 11 of box 3. A similar slot is
provided in the other side 12 of box 3 so the means for
tilting the table can be mounted on either side of the
box. A scale 21 is preferably provided to indicate the
angle at which the table 4 will be tilted. A stop 22 is
positioned within the slot 20 at the desired angle and
locked in place by lever 23. Once set for a particular
bit type, the angle is fixed and doesn't have to be
reset for each bit or button to be reground. A cylinder
24 is provided on the side 11 of the box 3 and the end
26 of the cylinder rod 25 is connected to the side 27 of
table 4 at point 28. When air is fed to cylinder 24,
extension of the rod 25 will tilt table 4 until further
extension is prevented by stop 22. As shown in Figure 4,
controls, generally indicated at 29, for tilting the
table and locking the bits) in place are provided at
the side 11 of the box 3. One switch 30 controls the
cylinder 24 for tilting the table 4 and a second switch
31 controls the locking cylinder 15 and pressure plate
14. Switches ~0, 31 to control the locking cylinder 15
and pressure plate 14 of the second aperture 13 and the
tilting of the table may be provided on the other side
12 of box 3. Flow controls are provided to regulate the
speed of movement of the table and the pressure plate.
The tilting means can be mounted on either side of the
box so that two boxes may be mounted side by side, while
leaving the tilting means easily accessible
Zarge down the hole bits to be reground
typically have a relatively long shaft that fits through
apertures) 13. In order to regrind smaller bits a floor
plate 32 that can be pivoted (slid) in and out of
position under aperture 13 is provided. Knob 33 and slot
34 in table 4 control the location of the floor plate
32. Adapters (not shown) for holding multiple small
sized bits can be inserted into aperture 13. An air-
actuated adapter having a pair of adjustable outer
plates to accommodate different sizes of bits and air
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actuated locking plates is preferred. Use of the
adapters eliminates repetitive set up time for the
operator.
A splash-guard 35 is provided at the front 37
of the box 3 that can be raised and lowered along a slot
36 on each side of the front 37 edge of box 3. A counter
balancing spring assists in the ease of operation of
splashguard 35. The splashguard 35 can be set and
retained at different heights as desired.
The arm system 6 for carrying and positioning
grinding machine 5 as noted previously is journaled onto
stand 7. With reference to Figures 1, 2, 4, and 6-9, the
arm system 6 consists a first arm section 39 having one
end 40 journaled to stand 7. The other end 41 of the
first arm section 39 is journaled to the backside 42 of
a first control box 43. The first arm section 39
controls the horizontal location of the grinding machine
relative to the bit to be reground. To the front side 44
of control box 43 is pivotally mounted 'a second arm
section generally indicated at 45. The second arm
section 45 consists of a pair of parallel arms 46, 47
with one end 48,49 of each arm 46,47 pivotally mounted
to the front side 44 'of the first control box 43. The
other end 50,51 of each arm 46, 47 is pivotally
connected to the backside 52 of a second control box 53.
The second arm section 45 controls the vertical movement
of the grinding machine up and down.
Within the second control box 53 (Figure 11),
is a rotation motor 54 and bearing arrangement 55 for
providing an orbital rotation to grinding machine 5. The
grinding machine 5 is attached to control box 53 by
means of plates 56. The grinding machine 5 has an
electric motor in the embodiment shown but can also
utilize an air or hydraulic motor. Each of the plates 56
is provided with an acruate slot 57. The angle of
attachment of the grinding machine 5 relative to control
box 53 can be adjusted by means of slots 57 and locking
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levers 58. By having the grinding machine slightly off
vertical, nipple formation on the button being reground
is minimized and uneven wear on the grinding cup
avoided.
5 A circuit board 60 is provided within the
second control box 53, said circuit board 60 containing
the control system for the grinding apparatus including
controls and microprocessor to control grinding time on
each button and grinding pressure. In the embodiment
10 shown pressure controls 61 are provided with digital
read outs on the front 62 of the second control box 53
to permit the operator to set, or increase or decrease
grinding time and grinding pressure. The microprocessor
can be used to provide other functions either manual or
automatic. For example, the microprocessor, in the case
of an electric motor, can monitor the amperage being
used and if it reaches a preset limit automatically
decrease the grinding pressure to prevent motor burn
out. The microprocessor can also control the flow of
coolant to the face of the button during grinding.
Within the first control box 43 (Figure 9), is
means to provide a balance pressure, generally indicated
at 63, to the arm or lever section that controls the
movement of the grinding machine in the direction of the
longitudinal axis of the button or bit when not in use
and grinding pressure when in use. In the embodiment
shown, the means to provide a balance pressure 63 to the
arm or lever section that controls the vertical movement
of the grinding machine is a cylinder 64 connected to an
end 49 of the lower arm 47 of the second arm section 45.
The end 49 of lower arm 47 extends out from the pivot
point 65 at which the lower arm 47 is connected to the
first control box 43. Cylinder 64 provides a balance
pressure to the second arm section when the grinding
machine is not in use and grinding pressure when in use.
The grinding pressure can be adjusted. In addition, b~
applying a controlled balance pressure while in zero
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grinding pressure mode, a lesser grinding pressure can
be achieved than that provided by gravity; effectively
increasing the available range of grinding pressure.
When grinding buttons the self-centering
aspects of the grinding machine tend to center the
grinding machine over the highest point on the button.
On buttons where wear is uneven, typically gauge
buttons, this may result in regrinding the button off
center from its vertical axis. One aspect of the present
invention provides means 66 to help align the grinding
machine with the longitudinal axis of the button to be
ground. In the embodiment shown the means 66 to help
align the grinding machine with the longitudinal axis of
the button consists of, a cylinder 67 (Figure 6) having
one end 68 connected to stand 7 and the other end 69
connected to the bottom 70 of the first arm section 39.
The cylinder 67 provides a side load to grinding machine
5 to help align the grinding machine with the
longitudinal axis of the button. In the embodiment
shown, the cylinder 67 is automatically activated when
the table 4 is tilted by the pilot feed from cylinder 24
through valve 71 (Figure 7). Valve 79 controls the water
flow. The side load biases the grinding machine to grind
more on either the outside or the inside of the gauge
buttons as required thereby tending to shift the
grinding machine over the true center of the button. The
means to help align the grinding machine with the
longitudinal axis of the button to be ground can
alternatively include a locking system to lock the arm
in place to prevent movement in a direction normal to
the longitudinal axis of the button while permitting
movement in the axial direction. Suitable side load can
also be provided by means other than by cylinder 67 such
as counterweights etc.
While typical grinding apparatus are aligned
so that the longitudinal axis of the bit is generally
vertical during grinding, in the case of very large
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bits, or in drilling equipment where bits or cutters are
mounted in a clustered pattern, grinding may be done
with the bit aligned horizontally or some other suitable
angle. The present invention is equally applicable to
this situation. In this situation the grinding machine
may be carried on an arm or lever system and the
grinding pressure applied in a horizontal or other
suitable direction.
As best illustrated in Figure 10, the
grinding machine illustrated utilizes a hex drive system
of the type described in U.S. Patent No. 5,639,273 and
U.S. Patent No. 5,727,994. In order to make the
operation of the apparatus operator friendly, means 72
are provided to easily align and attach the grinding cup
and detach the grinding cup after use. A spring-loaded
button 73 when depressed will fit into a slot in the
rotor 74 and prevent it from rotating. This enables the
operator to align the hex drive section of the grinding
cup with the drive section 75 of the rotor 74 and then
push the grinding cup on. To remove the grinding cup
after use the operator presses lever 76 towards the
grinding machine. The lever 76 pivots around point 77
and the extending arms 78 push the grinding cup away
from the drive section of the rotor facilitating removal
of the grinding cup from the grinding machine.
With reference to FIGURES 12 to 20 a second
embodiment of an improved grinding apparatus according
to the present invention is generally indicated at 100.
While the present invention is applicable to all
grinding apparatus having a grinding machine carried for
vertical and horizontal adjustment by an arm or lever
system journaled on a stand or frame and preferably with
a tiltable table for holding the bit to be ground, the
grinding apparatus shown is of the type intended to be
mounted on drill rigs, service vehicles or set up in the
shop, optionally installed inside a cabinet enclosure.
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The grinding apparatus 100 includes means 101
for holding one or more bits to be ground. In this
embodiment the means 101 for holding the bits) consists
of a frame 102 supporting a table 103. The frame 102, of
the illustrated embodiment, consists of a generally
rectangular box 104 having a back panel 105, left and
right side walls 106,107 normal to said back panel, two
extending support arms 108,109, a top plate 110, bottom
plate 111 and hinged cover 112.
A grinding machine 113 is carried by an arm or
lever system, generally indicated at 114, journaled on a
cylinder rod 115 of cylinder 116 attached to the frame
102. A compressed air connection is provided to operate
various aspects of the grinding apparatus as discussed
in detail below.
In order to minimize operator set up and
movement of the bit during regrinding, table 103 is
tiltably mounted to the frame 102 at pivot points
118,119 on the appropriate places of the extending arms
108,109 (see FIGURE 12 and FIGURE 18). The table 103 is
provided with one or more apertures 121 to hold one or
more bits to be ground. A bit (not shown) is positioned
in aperture 121 with the button to be ground in the
vertical position. The bit is held in place by pressure
plate 122 controlled by a locking cylinder 123. The
locking cylinder can be backed off slightly to rotate
the bit (to the next button to be ground) within the
aperture 121 without full release of the pressure on the
locking cylinder.
The grinding machine 113, in order to properly
regrind a worn button, should be aligned with the
longitudinal axis of the button. Accordingly to regrind
the gauge buttons, table 103 is tilted to correspond to
the angle at which the buttons are mounted in the bit.
The bit is then indexed in the table so that the
longitudinal axis of the button to be ground is in the
vertical. The means of tilting table 103 is best
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illustrated with reference to FIGURE 18 and 19. The
front edge 124 of right side 107 is bent to form an
inwardly extending flange 125. A longitudinal slot 126
is provided in flange 125. A scale 127 is preferably
provided to indicate the angle at which the table 103
will be tilted. A stop 128 is positioned within the slot
126 at the desired angle and locked in place by lever
129. Once set for a particular bit type, the angle is
fixed and doesn't have to be reset for each bit or
button to be reground. A cylinder 130 is connected to
stop 128 and the end 131 of the cylinder rod 132 is
connected to the side 133 of table 103 at point 134.
G~7hen air is fed to cylinder 130, retraction of the rod
132 will tilt table 103 until the rod is fully
retracted. As shown in FIGURE 12, controls, generally
indicated at 135, for tilting the table and locking the
bits) in place are provided on the instrumentation
panel 136 on the hinged protective cover 112. One switch
137 controls the cylinder 130 for tilting the table 103
and a second switch 138 controls the locking cylinder
123 and pressure plate 122. Flow controls are provided
to regulate the speed of movement of the table and the
pressure plate.
Large down the hole bits to be reground
typically have a relatively long shaft that fits through
aperture 121. In order to regrind smaller bits a floor
plate 139 that can be slid in and out of position under
aperture 121 is provided. Knob 140 and slot 141 in table
103 control the location of the floor plate 139.
Adapters for holding multiple small sized bits can be
inserted into aperture 121. Use of the adapters
eliminates repetitive set up time for the operator.
A splashguard 142 (see FIGURE 20) connected to
bottom plate 111 of frame 102 is provided at the front
of the grinding machine 113 that can be raised and
lowered.
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The arm system 114 for carrying and
positioning grinding machine 113 as noted previously is
journaled onto cylinder rod 115. With reference to
FTGURE 12 and 16, the arm system 114 consists of a first
5 arm section 143 having one end 144 journaled to cylinder
rod 115. The other end 145 of the first arm section 143
provides the mount for the second arm section 146. One
end 147 of the second arm section 146 is journaled to
the first arm section 143. The other end 148 of the
10 second arm section 146 is journaled to the back mount
149 connected to control box 150. Locking lever 151
allows control box 150, with back mount 149 to be moved
into position in relation to the axis of the second arm
section and then to be locked. Cylinder 116 through
15 cylinder rod 115 controls the vertical movement of the
grinding machine up and down. Cylinder 116 through
cylinder rod 115 provides a balance pressure to the arm
system when the grinding machine 113 is not in use and
grinding pressure/feed when in use. The grinding balance
pressure and pressure/feed can be adjusted.
Within the second control box 150, is a
rotation motor 152 and bearing arrangement 153 for
providing an orbital rotation to grinding machine 113.
The grinding machine 113 is attached to control box 150
by means of plates 154. The grinding machine 113 has an
electric motor i'n the embodiment shown but can also
utilize other motor type such as air or hydraulic motor.
Each of the plates 154 is provided with an arcuate slot
155. The angle of attachment of the grinding machine 113
relative to control box 150 can be adjusted by means of
slots 154 and locking lever 156. By having the grinding
machine oscillate slightly off vertical, nipple
formation on the button being reground is minimized and
uneven wear on the grinding cup avoided.
When grinding buttons, the self-centering
aspects of the grinding machine tend to center the
grinding machine over the highest point on the button.
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On buttons where wear is uneven, typically gauge
buttons, this may result in regrinding the button off
center from its vertical axis. To substantially align
the grinding machine with the longitudinal axis of the
button, the second arm section 146 is provided with a
cylinder 157 having one end 158 connected to the
cylinder 116 and the other end 159 connected to the
mount 160 of the second arm section 146. The cylinder
157 provides a biased load to grinding machine 113 to
help align the grinding machine over the button. In the
embodiment shown, the cylinder 157 is automatically
activated when the table is tilted by the pilot feed
from cylinder 130 through valve 161 in instrumentation
panel 136. The biased load causes the grinding machine
to grind more on the inside or outside of the gauge
buttons, as required, thereby tending to shift the
grinding machine over the true center of the button. The
suitable biased load can be provided by other means such
as counter weights, etc. Another method of aligning the
grinding machine with the longitudinal axis of the
button, in cases where deemed necessary, is by using one
or more cylinders) 157 connected to cylinder 116 and
cylinder rod 115 or frame 102 to lock the position of
grinding machine 113 in the plane normal to and aligned
with the longitudinal axis of the button to be ground.
Additionally or alternatively cylinders, mechanical
locks etc. can be incorporated to achieve the desired
effect. During grinding the grinding machine will then
grind the button in alignment with the button axis.
Other methods such as mechanical locks can also be used
for locking the horizontal distance or position in the
horizontal plane of grinding machine 113 from, for
example, cylinder 116 and cylinder rod 115 or frame 102.
Variations of the above described principle of
biased side loads, counter balancing and position
fixing, that can be used to allow for grinding at angles
other than vertical, are within the scope of the present
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invention. Combinations of variations of the above
described principle of biased side loads, counter
balancing and position fixing can be used to
substantially eliminate the need for tilting/pivoting
the bit when switching between grinding of face buttons
and gauge buttons. This principle would be ideal in
cases where tilting or pivoting of the bit is difficult
due to size, weight, etc.
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.
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.
