Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
The present invention relates generally to work tables and more particularly
to an inclined work
surface with a gantry assembly and counterbalancing system.
BACKGROUND
There are several types of supporting tables that have been suggested for the
use of tools, with
these tables providing support for these tools on the surface of the table or
by connection to the
underside of the table. Typically, these tables comprise a flat, generally
horizontally extending
top, which is supported by legs. The top of a supporting table typically has
an upper planar
surface which supports the item to be shaped and an under surface to which the
tool may be
attached. These horizontally extending tables require a large amount of floor
space in order to be
installed, thus drastically reducing the available work area. Furthermore,
these tables typically
require disassembly in order to relocate them from one room to another due to
restrictions of, for
example, the size of a doorway.
By inclining a supporting table the resulting floor footprint of the table is
dramatically reduced
when compared to that of a horizontal table having the same surface area. By
inclining the
supporting table, however, the tool which may typically be manoeuvred on a
plane parallel to the
surface of the supporting table, will be operating at an inclined angle. A
gantry on a horizontal
working table typically supports the weight of the tool being used, however
this support is
decreased if the working table is inclined.
As a result of the inclination of the table, the required applied vertical
force in order to translate a
horizontal gantry in a vertical direction will be increased, while the applied
force required for
horizontal translation of the tool positioned on the gantry will remain
relatively unchanged.
Thus there will be a variation in the required applied force necessary to move
the horizontal
gantry, depending on the direction of the translation. This variation in the
applied force may
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result in unsteady movement of the gantry resulting in uneven shaping or
etching through a laser
of the item being prepared.
Typically, in order to reduce the applied force necessary to move an object
vertically, a
counterbalance system is incorporated into the apparatus. A typical method of
counterbalancing
an object is achieved by the suspension of a weight using a pulley mechanism
such that this
additional weight counteracts the weight of the object. This technique
requires a plurality of
varying weights providing a means for the adjustment of the counter weight
enabling the
counterbalancing of objects of varying weights. U.S. Patent No. 5,806,245
describes the use of
this method as applied to the opening of a lift gate. Tn this example the
counterweight was
adjusted such that the full weight of the lift gate was compensated enabling
the user to easily
move the lift gate in a vertical direction.
Furthermore, pneumatic means have been used, for example, to open and close
gates, doors and
windows, for example. U.S. Patent No. 5,806,245 also describes a pneumatic
means enabling
the opening and closing of a lift gate; with the volume of the air within the
system being
controlled by a switch operated by a user. The force created within the
pneumatic means is
transmitted to the lift gate by a conventional pulley system. As the air
volume within the
pneumatic means increases the gate will rise and as the air volume within said
means decreases
the gate will lower. This pneumatic means was used to open and close the gate
only and the
pressure within said pneumatic means is not regulated to compensate for the
full weight of the
Iift gate enabling the user to easily move the gate in a vertical direction.
In a related patent, U.S. Patent No. 6,612,792 describes a pneumatic system
used in conjunction
with a worktable. It provides a work table for use with a tool, comprising an
inclined work
surface, which is substantially planar and is supported by a frame having a
base; a gantry
movably attached to the work surface and having two ends, a longitudinal axis
and extending
within a plane parallel to the work surface; a movable tool mount slidably
attached to the gantry
for removable attachment of the tool wherein the tool mount and the tool have
a combined
effective weight; a first movement means attached to one end of said gantry
for translation of the
gantry over said work surface; a second movement means attached to the tool
mount for
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translation of said tool between the ends of the gantry; and a weight
counterbalancing means
operatively associated with the tool mount fox neutralising the combined
effective weight.
Neutralisation of the weight is accomplished by attaching the tool mount to a
counterbalancing
system that counterbalances the combined effective weight of the tool and tool
mount along the
length of the gantry, enabling its smooth movements when the work surface is
in an inclined
position.
This background information is provided for the purpose of making known
information believed
by the applicant to be of possible relevance to the present invention. No
admission is necessarily
intended, nor should be construed, that any of the preceding information
constitutes prior art
againstthe presentinvention.
SUMMARY OF TIC INVENTION
An object of the present invention is to provide a work table having a gantry
assembly
counterbalancing system. In accordance with one aspect of the present
invention, there is
provided a work table for use with a tool, the work table comprising an
inclined work surface
which is substantially planar and is supported by a frame having a base; a
gantry assembly
including a gantry movably attached to said work surface, said gantry having
two ends, a
longitudinal axis and extending within a plane parallel to the work surface,
the gantry assembly
further including a movable tool mount slidably attached to said gantry and
configured for
removable attachment of the tool, wherein said gantry assembly has a combined
effective
weight; a first movement means operatively associated with said gantry for
translation of the
gantry over said work surface; a second movement means attached to the tool
mount for
translation of said tool and said tool mount between the ends of said gantry;
and a pneumatic
weight counterbalancing means operatively associated with said gantry for
neutralising the
combined effective weight of said gantry assembly.
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BRIEF DESCRIPTION OF THE FIGURES
Figure 1 is a side view of one embodiment of the present invention;
Figure 2 is a front view of the top half of one embodiment of the present
invention;
Figure 3 is an exploded view of the pulley mechanism in one embodiment of the
present
invention;
Figure 4 is an exploded view of the piston system in one embodiment of the
present invention;
Figure 5 is a front view of a counterbalancing system in one embodiment of the
present
invention;
Figure 6 is a front view of another counterbalancing system in one embodiment
of the present
invention;
Figure '7 is a front view of a counterbalancing system in one embodiment of
the present
invention;
Figure 8 is a front view of a counterbalancing system in one embodiment of the
present
invention;
Figure 9 is a front view of a counterbalancing system in one embodiment of the
present
invention; and
Figure 10 is a front view of a counterbalancing system in one embodiment of
the present
invention;
S
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DETAILED DESCRIPTION OF THE INVENTION
Definitions
The term "inclined vertical axis" is used to describe the axis which is
parallel to the inclination
of the work surface.
The term "effective weight" is used to describe the force component of the
gravitational weight
along the inclined vertical axis.
The term "gantry assembly" is used to describe a gantry together with a tool
mount secured there
to and/or a tool.
The term "tool" is used to describe a device where the operation of said
device would be affected
by the inclination of the surface upon which it is used, such as but not
limited to a router, panel
saw, laser, paint or ink applicator, sampling device, a cutting device and a
marking device.
The term "tool mount" is used to describe a device which allows attachment of
a tool to the
apparatus of the present invention such that the tool is oriented in an
operational position. It
would be readily appreciated by a worker skilled in the art that the tool can
be removably or
permanently attached via the tool mount.
Unless defined otherwise, all technical and scientific terms used herein have
the same meaning
as commonly understood by one of ordinary skill in the art to which this
invention belongs.
The present invention provides a work table for use with a tool, comprising an
inclined work
surface, which is substantially planar and is supported by a frame having a
base.
The work table further comprises a gantry assembly having a combined effective
weight,
wherein the gantry assembly includes a gantry movably attached to the work
surface and having
two ends, a longitudinal axis and extending within a plane parallel to the
work surface. The
CA 02548879 2006-05-29
gantry assembly further includes a movable tool mount slidably attached to the
gantry for
removable attachment of a tool. The work table further comprises a first
movement means
attached to one end of said gantry for translation of the gantry over said
work surface and a
second movement means attached to the tool mount for translation of said tool
between the ends
of the gantry. Furthermore, the work table comprises a weight counterbalancing
means
operatively associated with the gantry fox neutralising the combined effective
weight of the
gantry assembly.
Neutralisation of the weight is accomplished by attaching the gantry to a
counterbalancing
system that counterbalances the combined effective weight of the gantry
assembly enabling its
smooth movements in the inclined vertical axis.
In the apparatus of the present invention, the effective weight of the gantry
assembly along the
length of the work surface is zero when the work surface is in the horizontal
position. As the
work surface is raised to an inclined position, the effective weight of the
gantry assembly along
the length of the inclined surface increases, rendering the ability to support
and raise the gantry
assembly along the height of the work surface (the inclined vertical axis)
increasingly difficult.
The counterbalancing means of this invention generates a force equal in
magnitude to counter-
act the combined effective weight of the gantry assembly along the height of
the work surface
(the inclined vertical axis), wherein the generated counter-force is applied
by a flexible line
attached to the gantry, wherein said flexible line is carried by a pulley.
In one embodiment of the present invention and with reference to Figure 1, the
apparatus is
mobile with this mobility being provided by a rolling mechanism 10, for
example casters or
wheels which are connected to the base of a supporting frame 20. The apparatus
can be
transported to a desired location and the subsequent activation of a braking
system maintains the
desired location of the apparatus. The inclination of a work surface 30
reduces the floor
footprint of the apparatus and thus there is a reduction in the floor area
required to set-up said
apparatus as compared to a horizontal work surface having the same surface
area. Furthermore,
by inclining the work surface 30 the apparatus may be able to move through
standard doors,
resulting in easy relocation of said apparatus. Material 40 may also be easily
installed on the
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work surface 30. Such material may include, but is not limited to, stone,
granite, glass, wood
acrylic, carpet, and leather.
In a further embodiment of the present invention, the supporting frame may be
constructed such
that the inclination of the work surface may be adjusted or fixed at a
particular angle depending
on the preference of the user. The adjustment of the inclination of the work
surface may be
performed by a variety of means, for example manual, mechanical or electrical
as would be
known to a worker skilled in the art. The inclined work surface may be
inclined at an angle
within a range of 0 to 90 degrees from the vertical axis emanating from the
base of the
supporting frame. In an embodiment of the present invention, the inclined work
surface is
inclined at an angle between 0 to 45 degrees from the vertical axis. Fn
another embodiment, the
inclined work surface is inclined at an angle between 10 to 25 degrees. In
still a further
embodiment, the inclined work surface is inclined at an angle of 22.5 degrees.
Gantry Assembly
In one embodiment of the present invention and with reference to Figure 2, the
gantry 50
comprises a main elongated tubular member. Although it is not necessarily so,
the components
of the gantry 50 can be designed such that a tool is able to reach all corners
of the inclining work
surface 30. In a related embodiment the elongated tubular member spans the
width of the wark
surface.
In one embodiment of the present invention and with further reference to
Figure 2, a tool mount
may be connected to the gantry 50 such that the tool mount is able to move
smoothly and freely
along said gantry 50. For example, the tool mount can incorporate a collar
which can be
mounted on the gantry 50, providing a means for said member to guide the
translation of the tool
mount along its length. The smooth and free movement of the tool mount along
the gantry 50
may be provided by a plurality of guide bearings, or any other friction
reduction means, for
example various lubricants. A tool connected to the tool mount is capable of
freely moving along
the length of the elongated tubular member of the gantry and together with the
gantry, over the
work surface such that the tool can translate over a defined area of the work
surface. In one
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CA 02548879 2006-05-29
embodiment of the present invention the defined area is the entire work
surface. Guide rails b0
are also provided along the side extremities of the inclined work surface 30.
The smooth and
free movement of the gantry 50 along said guide rails GO may be provided by a
plurality of guide
bearings. A variety of alternate guiding means providing substantially
frictionless movement of
the gantry would be known to one skilled in the art.
In one embodiment of the present invention, the tool 70 is firmly attached to
the tool mount 75
using adjustable brackets, or any other means that can firmly connect the tool
to the tool mount.
In one embodiment of the present invention the translation of the tool is
controlled by a
computing system. This computing system controls a series of electrical means,
for example
speed reduction motors and/or electro servo motors, which provide a means for
the movement of
the tool using a gearing mechanism. Electrical means control the movement of
the gantry over
the work surface and another electrical means controls the movement of the
tool mount along the
length of the elongated tubular member. In one embodiment, a further
electrical means may be
installed to enable the movement of the tool in a direction perpendicular to
the plane of the
inclining work surface, with this electrical means being incorporated into the
tool mount
assembly. The control of the movement of the tool, tool mount and gantry using
electrical means
would be known to a worker skilled in the art of CAD/CAM systems (computer
aided design/
computer aided manufacturing). For example, a CAD/CAM system provides a means
for a
designer to create a virtual representation of the object to be manufactured
using a computer, or
format of computing device as would be known to a worker skilled in the art.
The computing
device can subsequently create a set of instructions for the system to
manufacture the desired
object, where these instructions control the apparatus in the desired manner.
Counterbalancing Means
The counterbalancing means of the present invention counter acts the combined
effective weight
of the gantry assembly along the inclined vertical axis. This counterbalancing
force remains
constant independent of the position of the gantry and the tool over the work
surface.
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Furthermore, this counterbalancing means enables equilibration of the required
applied force for
the translation of the gantry assembly over the work surface.
In one embodiment of the present invention and with reference to Figure 2, the
counterbalancing
means incorporates a pulley mechanism comprising pulleys, flexible lines 80
and 90, pneumatic
cylinders 100 and 110 and a pressure controlling system. Flexible line 80 is
associated with
pneumatic cylinder 110 and flexible line 90 is associated with pneumatic
cylinder 160. In this
embodiment, the pneumatic cylinders 100 and 110 are parallel to each other and
offset.
In one embodiment of the present invention and with reference to Figure 3 and
Figure 4, the
flexible line 80 connected to the piston 130 in pneumatic cylinder 110 is
relayed to one end of
the gantry by a conventional pulley 120. The pressure within the pneumatic
cylinder 110 is
monitored and regulated by the pressure control system, which initiates the
insertion or removal
of air from the pneumatic cylinder through a valve 140 (e.g. hose) such that a
predeternuned
internal pressure within the pneumatic cylinder is maintained. A pressure
sensor monitors and
helps to regulate the pressure within said cylinder such that a constant
pressure is maintained
within the cylinder at all times. In one embodiment of the present invention,
a safety valve can
be installed W thin the pneumatic system to prevent pressure lcss Am case of
breaks in the - -- -
pressurized supply lines. Pneumatic cylinder 100 has similar components as
described for
pneumatic cylinder 110. ,
In one embodiment of the present invention the pressure sensor is operatively
coupled to a
computing device, wherein the computing device can sample the pressure within
a pneumatic
cylinder and regulate the pressure therein through a feedback type loop. For
example the
feedback loop can be configured to sample the pressure at predetermined
intervals of time or
sampling rate, for example every one second, two seconds, 10 seconds, 30
seconds or 1/10 of a
second, in order to maintain a desired pressure within a pneumatic cylinder.
For example the
computing device can adjust the sampling rate of the pressure sensor based on
the amount and
speed of required movement of the gantry relative to the work surface. A
worker skilled in the
art would readily understand haw to configure a computing system in order that
the desired
function of the pressure feedback loop is enabled.
CA 02548879 2006-05-29
In one embodiment of the present invention, the computing device which
regulates the pressure
within the pneumatic cylinder can be integrated with the computer system
configured tv control
the movement of the toot, tool mount and gantry.
In one embodiment of the present invention and with further reference to
Figure 2, the pulley
mechanism and the pneumatic cylinders 100 and 110 are positioned on the top
edge of the
inclined work surface 30. The gantry 50 is counterbalanced by flexible lines
80 and 90 such as
cables which are connected to the gantxy SO and which are carried by
conventional pulleys
mounted near the pneumatic cylinders 100 and 110. The flexible Junes 80 and 90
extend through
an opening in the pneumatic cylinders 100 and 110 and are attached to pistons,
which are
movably disposed inside the pneumatic cylinders 100 and 110. Thus the movement
of the gantry
50 is directly linked to the movement of the pistons. As the gantry 50
translates over the inclined
work surface 30, the pistons will translate a corresponding distance within
the pneumatic
cylinders 100 and 110, altering the volume of the air within the pneumatic
cylinders 100 and
110. This translation of the pistons results in a pressure change within the
pneumatic cylinders
100 and 110, with said pressure being monitored by pressure sensors and
accordingly adjusted to
a desired level for the counterbalancing of the gantry assembly.
1n one embodiment of the present invention and with further reference to
Figures 3 and 4, the
apparatus comprises sealing means 150 located on the piston 130, the top of
the pneumatic
cylinder 110 and the entry location of the flexibte line 80 into the pneumatic
cylinder 110. An
example of such a sealing means includes what are known in the art as "O
rings" or any other
sealing means, which result in similar sealing qualities. These sealing means
1~0 provide the air
seal between the piston 130 and the internal wall of the pneumatic cylinder
110, with said sealing
means 150 attached directly to the piston 130 enabling the movement of the
piston 130 within
the pneumatic cylinder 110 while maintaining said pressure seal. Similar
sealing means 155 are
installed at the entry point of the flexible line 80 into the pneumatic
cylinder 110, enabling the
sealing of the pneumatic pressurized chamber in front of the piston inside
cylinder 110 during
the movement of the flexible line 80.
I1
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In another embodiment of the present invention and with reference to Figures
5, 6 and 7, the
counterbalancing system comprises two pneumatic cylinders. In Figure 5,
pneumatic cylinders
100 and 110 are aligned and mating at one point. Flexible lines 80 and 90
extending from
pneumatic cylinders 100 and lI0 are connected to the gantry 50 through pulleys
120 and 160. In
another embodiment and with further reference to Figure 5, the pneumatic
cylinders 100 and 110
can be combined into a single cylinder comprising both pistons 130 and 170. In
this case the
central portion of the cylinder should be vented to allow air movement into
and out of this region
during movement of the pistons. Such an embodiment requires that the pneumatic
cylinder be of
a sufficient length enabling the pistons 130 and 170 to travel the required
distance to enable
movement of the gantry over the desired area of the work surface and to
properly counterbalance
the gantry assembly as required under the present invention. The
counterbalancing system of
Figure 6 comprises pneumatic cylinders 100 and 110 which are positioned along
the side edges
of the work surface 30. The counterbalancing system of Figure 7 comprises
pneumatic cylinder
100 positioned along the top edge of the work surface 30 and a pneumatic
cylinder 110
positioned along the bottom edge of the work surface 30. As would be known to
a worker
skilled in the relevant art the flexible line and pulley mechanism may take a
variety of
configurations which still provide the required counterbalancing force to the
gantry in order to
counterbalance the effective weight of the gantry assembly.
In another embodiment of the present invention and with reference to Figures
8, 9 and 10, the
counterbalancing system comprises a single pneumatic cylinder 100 which may be
positioned
either at the top or side edge of the work surface 30. The counterbalancing
system of Figure 8
comprises two flexible lines 80 and 90 connected to the piston head 130. The
counterbalancing
systems of Figures 9 and 10 require a suitable guiding rail system for the
gantry 50 given the
presence of a single flexible line 80. The embodiments illustrated in Figures
9 and 10 may cause
the gantry 50 to rotate during its movement unless a proper guiding rail
system is provided as
would be known by a worker skilled in the relevant art.
Pressure Control System
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In one embodiment of the present invention, upon detection of a decrease of
the internal pressure
within the pneumatic cylinders by the pressure sensors, the pressure control
system will initiate
the insertion of compressed air from a compressed air source such as an air
compressor into the
pneumatic cylinders through valves. This insertion of air will continue until
the internal air
pressure has reached the desired level. Conversely, the pressure control
system, upon detection
of an increase in the pressure within the pneumatic cylinders by the pressure
sensors, will bleed
air from the pneumatic cylinders through valves until the internal air
pressure has decreased to
the desired level. A pneumatic cylinder pressure in excess of that desired may
cause the gantry to
rise and conversely the gantry may fall if the pneumatic cylinder pressure is
below that which is
required. The pressure sensors which are attached-to the valves and monitors
the pressure within
the pneumatic cylinders, are sufficiently sensitive such that the required
internal pressure within
the pneumatic cylinders will be maintained by the pressure control system, to
within far
example, ~0.05 psi of the pre-selected pressure. There are a variety of
pressure control systems
which are capable of providing this level of sensitivity with one such system
being manufactured
by NUMATICSTM. See also Willcerson~ (e.g. see Precision Regulators Application
Guide FRL-
APP-C00, July 2004, http://www.wilkersoncorp.com~brochure/FRL-APP-600.pdf)
A type of pressure control system may be embodied by a pneumatic pressure
regulator, also
known as a pressure-reducing valve which reduces pressure from supply to
output. The
regulator is used to control and kip the reduced pressure constant or at least
stabilized when
either the primary or secondary pressure fluctuate. A common use of the
regulator is to make air
driven devices operate consistently with constant pressure for functions
involving force, torque,
speed, control and finesse. The regulator valve opens, closes and modulates on
demand to keep
the pressure constant. This is a balance between the force (spring tension)
set to control the
pressure and the internal force of the compressed air attempting to close it.
A feature common to
many regulators is relieving capability, The energy required to compress the
valve spring force,
open the valve and stabilize the moving parts is reflected in initial pressure
drop. When the relief
passage opens the excess pressure will vent from the regulator without further
pressure increase
up to maximum relief flow. When the maximum relief flow is exceeded the outlet
pressure will
increase. This is how a "high relief' regulator, which may be used in one
embodiment of the
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invention, operates. See White Paper #8, Air Regulators, by Thomas W. Kreher,
Applied
Pneumatic Controls, http://www.ifps.or~/Education/WhitePaperslAirRe ators.htm.
In one embodiment of the invention wherein there are two pneumatic cylinders,
the pressure
control system is monitoring pressure within only one cylinder. In this case,
the pressure control
system applies the determined adjustment to both cylinders. Alternatively,
there may be a
pressure control system associated with each of the pneumatic cylinders for
controlling the
pressure therein independently.
The required speed of response of the pressure control system to a change in
the internal pressure
of the pneumatic cylinders is directly linked to the translational speed at
which the gantry is
being moved. For example, rapid movement of the gantry will result in sudden
changes in the
volume of the air chamber within the pneumatic cylinders and thus the
regulation of the internal
pressure within said cylinders must be equilibrated at a faster rate in order
to maintain a
consistent counterbalancing force.
The pulley mechanism transmits the force generated within the pneumatic
cylinders to the gantxy
and thus counterbalances the combined effective weight of the gantry assembly
along the
inclined vertical axis. The force transmitted via the flexible Iines is
equivalent to the pressure
within the pneumatic cylinders times the surface area of the piston. Thus, by
maintaining a
constant pressure within the pneumatic cylinders, even during volumetric
changes of the air
chambers within said pneumatic cylinders, a constant counterbalancing force
will be exerted on
the gantry.
By counterbalancing the combined effective weight of the gantry assembly the
required power
associated with an electrical means that translates the gantry over the work
surface, is reduced.
Furthermore, this counterbalancing means may reduce the wear of the components
of the
electrical means due to the reduction of the weight being translated in
comparison to a situation
in which the tool is translated in the absence of the counterbalancing means.
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In one embodiment of the present invention the desired pneumatic cylinder
pressure is
determined based upon the effective weight, along the inclined vertical axis,
of the gantry
assembly. The pressure within the pneumatic cylinder may be systematically
increased until the
gantry assembly reaches a state of weight neutrality. At this point the
combined effective weight
of the gantry assembly is completely counter acted by the counterbalancing
mechanism, as such
the gantry assembly will remain at a constant position until movement of said
gantry assembly is
initiated. Upon the determination of the required internal pneumatic cylinder
pressure, the
pressure sensor is calibrated to this value for the subsequent operation of
the apparatus. As
would be readily appreciated by a worker skilled in the art upon the
adjustment of the inclination
of the work surface, the counterbalancing system must be re-calibrated. The
same is true if the
tool associated with the gantry is changed.
The present invention provides a means for counterbalancing the combined
effective weight of a
gantry assembly which is being used in conjunction with an inclined work
surface. By
counteracting the combined effective weight of the gantry assembly using
pneumatic means, the
varying weights of the gantry assembly (which may occur through the variation
of various tools
used on the gantry) operated using the present invention are counterbalanced
by adjusting the
internal pressure within the pneumatic cylinder.
The invention being thus described, it will be obvious that the same may be
varied in many
ways. Such variations are not to be regarded as a departure from the spirit
and scope of the
invention, and all such modifications as would be obvious to one skilled in
the art are intended to
be included within the scope of the following claims.
IS
