Note: Descriptions are shown in the official language in which they were submitted.
BAND ~W APPARATUS AN13 P~ET~OD
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~ECHNICAL FIELD
~he present invention re~ ates, in general, to
bz.nd saw apparatus suitable f or cutting relatively hard
metal object~ and, more particularly, relates to a band saw
: aE~paratus and a method for enhancin~ the cutting ra~es~ the
cu~ing precision arld the blade life by minimizing ~he area
o~ the workpiece engaged by the cuttinq edge of the blade
dl:~ring cuttingO
1 0 E~KGF~c)uNr)~
~' Various at~empts ha~te been: made 'co enhance the
cutting rate c~f a band saw ~dhen cutting hard materials.
One approach i5 to form the band saw blade w~th a height
dimension ~hich~ varies along the length of the bladec
Typical of such efforts is the apparatus set forth in
United Stat:es Patent Nos7 4,205,571, d~,l95~543, ~,160,397
and 4 ,023 ,448. Irl these patents an endless band saw blade
is ormed with a varying heigh'c dimension or side
elevationAl pro~ ile so that~ as the height Yariations pa~
over guide meansD the blade is urged toward and then
.~ permitted to move away f rom th~ workpiece,.
.... ... , .. ... . . . . . ~ .. . . . . ....... .. ....
1 In most cases such specially formed band saw
blades are actually employing a well known principle for
improving cutting efficiency, namely, they are formed to
reduce the area being engaged ~y the saw teeth by see-
sawing the blade as it is advanced. (See, e.g~, United
States Patent No. 4,160,397, column 2 lines 37-41 and
United States Patent No. 4,205,571, column 2l lines 7-10)
In some cases the blade is formed and the guides are set to
displace the blade directly toward the workpiece without
see-sawing or rocking, but more typically there is angular
displacement.
When hard metallic workpieces are be~ng cut, the
saw blade teeth tend to be displaced into the workpiece
only to a small degree before there is a reaction force
which tends to move the saw arm (or drive wheel support
frame) away from the workpiece~ Thus, a~ter some initial
set or small penetration of the teeth into the work, the
remainder o the displacement resulting from blade height
variations tends to produce upward movement of the saw arm
away from the workpiece. Since band saws typically include
; a pneumatic or hydraulic feed cylinder and control circuits
and associated feed linkage which control the rate at which
i the saw is advanced through the workpiece, the feed
cylinder and control circuit act as a constraint against
free movement of the band saw.
In some saws the feed cylinder and control
circuitry will not let the arm back rapidly away from the
workpiece to accomodate variations in blade height which
are greater than the initial set of the teeth into the hard
; 30 metallic workpiece. This will cause the saw blacle to bend
and to he stressed.
88~
In other saws, the feed assembly will allow the
saw to move away from the workpiece as the blade height
increases, but will not allow a rapid return toward the
workpiece as the valleys in the blade are passed over the
blade guides. If the return toward the workpiece which is
induced by the valleys in the blade height is at rate which
is greater than the feed rate, the feed cylinder and
control circuit retard the arm movement to the saw arm back
toward the workpiece feed rate. Such retarding or slowing
of the saw arm movernent results in a dramatic reduction in
cutting force while the saw arm tries to catch up to the
blade displacement. In the extreme the force will be zero
and stressful bouncing and bending of the blade will occur.
This cutting force reduction reduces cutting efficiency
during part of the cutting process, although the overall
efficiency is improved as a result of the improvement
during the portion of the cut in which the blade is being
urged toward the workpiece and the arm is rebounding away
from the workpiece.
Although not specifically recognized in the prior
art, the effect of the feed cylinder constraint has
heretofore been accommodated in one of two ways.
First, the height variation along the blade can
be selected so that it i5 not substantially greater than
the depth to which the teeth can be initially set or driven
into the work. The disadvantage of this "solution" is that
it does not maximize cutting efficiency.
A second approach is to spread the blade guides
from the workpie~e suf~iciently to enable bending of the
saw blade along the lonyitudinal axis of the blade to
accomodate restraint in either the movement toward or away
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1 from the workpiece. This results in bo~wing of the blade
; and produces angular variations which reduce the see-sawing
effect. This "solukion," however, is very disadvantageous
in that it can fatigue the blade, and it will cause
wandering of the blade as it cuts through the work. The
amount of deviation of the saw blade from a straight line
cut is proportional to the third power of the separation of
the guides from each other.
If the blade guides are set next to the workpiece
so that blade bending is insignificant, and if the height
variation is too great, feed cylinder constraint will cause
the teeth to dig into the workpiece to a degree which will
either stop khe saw or shear off the teeth from the blade.
Since this possibility is unacceptable, specially formed
prior art blades either have had limited height variations
; or have been used with blade guides which are spaced from
the workpiece, or compromises o both approaches.
Ideally, however, enhance cutting efficiency is
obtained when the teeth are urged into the workpiece beyond
the initial set to just short of digging in to a point
which would stop the saw or shear the teeth. For maximum
efficiency in the cutting of a hard metallic material, the
! teeth should be forced into the material until they start
to dig in so they will cut and pull a chip and then the
teeth should be released before shearing or stalling of the
saw.
Moreover, the cutting force should be applied and
maintained as a substantially constant force, below the
force which will cause the teeth to dig in, for as long as
possible during the entire blade displacement cycle.
Additionally, and most preferably, the area being cut at
38
1 any time should be minimized by see-sawing or rocking of
the saw blade so as to increase the pressure per unit area
of the teeth and ease penetration of the material being cut
without having to increase the total Eorce on the blade.
Specially formed saw blades have other
disadvantages. It is inherent that in a sinusoidall
stepped or otherwise specially formed blade the areas of
the blade which project outwardly toward the workpiece the
farthest will undergo the greatest amount of stress and
wear. Thus, over the length of a band saw blade, all of
the downwardly projecting areas will tend to wear first and
to have the greatest potential for blade ~atiguing stress
risers.
I~ is possible to change specially formed blades
to vary the amplitude of blade displacement and thus to
; some degree, the see-saw cutting action and pressure
applied, and it also is possible to vary the cutting speed
to change the frequency of pressure variation. These
changes, however, are not easily or quickly accomplished.
For band saw apparatus in which the production runs are
short and the materials being cut are changed frequently,
for example~ in a job--shop, repeated blade changing can be
a substantial disadvantage.
Another approach to achieving a see-saw cutting
action and thereby varyinq the pressure applied by a band
saw blade during cutting is disclosed in United States
Patent No. 4,127,045. In this patent a pivotal arm band
saw is shown which has a blade guiding assembly that is
ormed to displace the saw blade toward and permit movement
away from the workpiece b~ a stepcam and follower.
The cutting dynamics for the apparatus oE United
1 States Patent No 4,127,045 are the same as above described
for specially formed blades. As the cam pushes the blade
toward the workpiece and saw table, the blade flexes
between the blade guides and the workpiece because the arm
feed cylinder resists reaction displacement of the arm
upwardly.
The guides in United States Patent No. 4,127,045
are widely spaced Erom the workpiece which will permit
blade flexure. Displacement of the blade toward the work
table by one guide does change the angle of engagement of
the workpiece with the work to enable a see-saw cutting
action~ but the wide setting of the guides and the
constraint of the cutting arm by the feed cylinder inhibit
the effectiveness o~ such see-saw action and the depth to
which the teeth are driven into the workpiece.
Generally it is well known in the cutting art,
and particularly in connection with power hack saws and
power grinders, to vary the angle of cutting during the
cut. MARVEL brand hack saws, produced by Armstrong-Blum
~anufacturing Co. o~ Chicago, Illinois~ for example, have
for many years used a "Roll Stroke" blade motion which
progressively raises one end of the saw blade while
lowering the other as the blade is drawn through the work~
This action is repeated many times over the full cut of the
workpiece.
Grinders similarly have been constructed in which
the pivotal arm upon which the abrasive wheel is mounted is
itself eccentrically mounted to displace the pivot point of
the arm and thereby vary the area being cut. It also is
common machining practice to rotate or roll the workpiece
as it is cut to reduce the area engaged at any time by the
~ 2S~
1 cutting tool, and all of these methods maintain higher unit
cutting forces by reducing the cutting area.
In the same manner as see-sawing reduces the area
of a workpiece being engaged bY the saw blade, the shape of
the workpiece, and particularly the width dimensionr can
effect the cutting rate substantially. A piece of round
stock, for example, initially presents a relatively small
area (length along the blade) to be cut. As the blade cuts
through the cylinder, the area increases until the center
of the workpiece is reached. The area of the workpiece
along the blade which is being cut then dlminishes as the
blade moves down to the bottom of the workpiece.
The effect of the changing area of engagement of
the saw blade with the workpiece as a function of workpiece
shape on the efficiency of cutting workpieces has not been
~ considered in any detail~ While see-sawing the blade
;~ and/or using specially formed stepped or wavy blades
enhances efficiency, the effeciency of cutting a workpiece
can be further enhanced by considering workpiece width at
various times during the cut and making adjustments to saw
performance characteristics such as feed rater blade
~ oscillation, cutting pressure and/or blade speed.
'~ Moreover, such variations also can be used to enhance
cutting effeciency in connection with conventional non-
oscillating or non-vibrating saws.
It i5 an object of the present invention to
provide band saw apparatus and a method for cutting hard
workpieces which enhances cutting efficiency and yet
maintain substantial blade life.
It is another object of the present invention to
provide band saw apparatus and a method in which the
; 1 advantages of see-saw cuttinq are combined with ~he
advantages of a more optimum depth o~ penetration of the
blade teeth into a hard workpiece to improve cutting
efficiency.
It is a further object of the present invention
to provide band saw apparatus in which the frequency,
ampIitude, displacement speed and duration of cutting along
a given area can be varied without regard to cutting speed
or blade configuration to enable tuning of cutting to the
specific workpiece being cut.
Another object of the present invention is to
provide band saw apparatus and method in which the angle of
engagement of the workpiece by the cutting ~dge of the
blade and the see-sawing cutting action can be more
efficiently varied during cutting so as to enhance the
efficiency and reduce the time of cutting.
Still a~further object of the present invention
is to provide a method for cutting a metallic workpiece
which affords greater cutting efficiency, while minimizing
cutting blade fatigue, and to distribute wear along the
total length of the blade.
Still another object of the present invention is
to provide a method for cutting a hard metallic workpiece
or the like which reduces the set up time between the
cutting oE different materials or objects, provides the
user with greater flexibility and control during cutting.
and allows tailorin~ of cuttinq to the shape oP the
workpiece being cu~.
Another obiect of the present invention is to
provide an improved method for cutting workpieces having a
width dimension which varies with the depth of cut.
1 S~ill a further object of the present invention
is to provide band saw blade displacement apparatus which
can be easily adapted to existing ~and saws to enhance
cutting efficiency and which can be employed on both
vertical and horizontal band saws.
Still another object of the present invention is
to provide band saw apparatus which is durable, easy to
use, and employs standard band saw cutting blades.
The band saw apparatus and method of the present
invention have other features and obiects which will be
apparent from, or are set forth in more detail in, the
accompanying drawing and following description of the
preferred embodiments.
The band saw apparatus of the present invention
includes blade drive means Eormed for support and guided
movement of a saw blade for cutting a workpiece and
including movable carriage means, an endless band saw blade
mounted to the drive mean~, feed means coupled for relative
advancement o~ said carriage means toward said workpiece
and displacement or reciprocation means formed to produce
variation of the cutting area of the workpiece during
movement of the saw blade.
In one aspect, the improvement in the band saw
apparatus of the present invention comprises, briefly, the
feed means being ormed for and disengaged from advancement
of the carriage means to permit substantially unconstrained
movement of the carriage toward and away from the workpiece
in response to displacement of the saw blade by said
displacement means toward the workpiece.
In the preferred form, blade guides include guide
block elements mounted in sliding engagement with a back
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1 edge of the saw blade, and the guide elements are in turn
mounted on and coupled to (directly or through levers)
fluid actuators so that displacement at relatively spaced-
apart locations along the back edge of the blade toward and
away from the workpiece can be accomplished.
The frequency, amplitude~ displacement speed,
duration and phasing between the two spaced-apart
reciprocating guide assemblies also can be independently
varied so as to tune vibration and cutting area variations
to the specific material and object being cut for a maximum
cutting efficiency.
Disengaging the feed means to free the carriage
for reaction to blade di~placement prevents digging in of
the teeth~ allows a more constant cutting force to be
applied during the cut, and permits the guides to be set in
close proximity to the workpiece for greater cutting
accuracy.
FOL workpieces of varying width dimension over
the depth of the cut, the band saw apparatus preferably
!~ 20 includes guides which are movable and can be laterally
displaced during cutting so as to be position as close to
the workpiece as possible during the entire cut.
Additionally, the sawing apparatus includes a controller,
most preEerably a computerr for varying, over the depth of
cut, the feed rate, the displacement parameters of the
blade, and the blade speed, all as a function of the width
of the workpiece being cut.
The method of cutting a workpiece of the present
invention includes the steps of moving a saw blade across
3~ the workpiece to effect cutting and simultaneously varying
- the force per unit area of the blade against the workpiece.
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1 In the improved method of the present invention,
the displacement occurs with the band saw frame or carriage
being free to move toward and away from the workpiece as
may be required. ~oreover, the rate of feeding of the saw
blade is varied to accommodate changes in the width
dimension of the workpiece over the depth of cuto
BRIEF DESCRIPTI~N QF TE~E_DR~WINGS
FIGURE l is a side e1evational view of the arm
portion of a pivotal arm, horizontal band saw with the
wheel housing removed and including the blade displacement
apparatus of the present invention.
FIGURE 2 is an enlarged, fragmentary, cross-
sectional view of the area bounded by line 2-2 in Figure l
showing blade displacement apparatus constructed in
accordance with the present invention.
FIGURE 2A is a fragmentary, side elevational
view, in cross section of an alternative embodiment of the
; fluid cylinder of Figure 2.
FIGURES 3, 4 and 5 are fragmentary, side
elevational views of band saw guide assemblies constructed
in accordance with the present invention with the blade
displaced upwardly on the righthand side of the
displacement apparatus, both guides in a neutral position,
and the blade displaced upwardly on the lefthand side of
the apparatus, respectively.
FI~URE SA is a fragmentary~ side elevational view
of an alternative embodiment o band saw guide assemblies
constructed in accordance with the present invention.
FIGURES 6, 7 and~8 are enlarged, cross-sectiQnal
views through a workpiece illustrating the method of
cutting a round workpiece of the present invention.
1~5~B8~
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1 FIGURE 9 is a side elevational view and schematic
diagram corresponding to Figure 1 of an alternative
embodiment of the present invention.
BEST MODE OF CARRYING OUT T~E
XNVENTION AND INDUSTRIAL_~PPLICABILITY
The method and apparatus of the present invention
are suitable for use with a wide variety of horizontal and
vertical band saws. For purposes of illustration, Figure 1
shows a horizontal, pivotal arm, band saw constructed in a
manner more fully setforth in my United States Patent No.
3,682,030, but having mounted thereon the band saw blade
displacement apparatus of the present invention.
Band saw 21 includes a horizontally extending arm
22 which is pivotally mounted at 23 to mountinq flange 24
extending upwardly from base 26 of the saw. Rotatably
mounted pLoximate opposite ends of arm 22 are a drive wheel
27 and an idler wheel 28 upon which an endless band saw
blade ~9 is movably mounted~ Saw blade 29 advances in the
direction of arrow 31 across a cutting stretch 32 between a
pair of spaced-apart guide assemblies 33 and 34. Arm 22
acts as a movable frame or carriage means which can be
advanced toward the workpiece as the saw blade cuts through
the workpieceO
As will be understood. however, the use of a
pivotal arm band saw for purposes of illustration shall not
limit the applicability of the apparatus and method of the
present invention to such saws, and the present invention
may be easily adapted for use with either horizontal or
vertical band saws with frames or carriages which do not
pivot.
Pivotal arm band saw 21 can be displaced in the
direction of arrows 36 and 37 by pneumatic lift cylinder or
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l feed means 38 mounted on base 26. The arm is initially
lifted upwardly in the direction of arrow 36 until it is
above a workpiece (shown in Fig. 6; not shown in FigO 1 but
normally held by vice means 39). Cylinder or feed means 38
then allows the saw arm to pivot about mount 23 downwardly
in the direction of arrow 37 as a saw blade is advanced so
as to cut the workpiece~
In many band saws. lift cylnder 38 actually
supports arm 22 as it descends so that the full weight of
the arm is not applied as the saw cuts through the
workpiece. In some saws, however, the cylinder will add to
the weight of the arm to produce the desired cutting force
and feed rate.
In most band saw apparatus, feed cylinder 38
15 includes a flow control valve means (not shown in Figure 1,
but shown at 185 in Figure 9), which enables selective
control of the ra~e at which a working fluid can escape
from cylinder 38; this controls the rate at which arm or
carriage means 22 descends toward the workpiece. Moreover,
it is usually possible to effectively disengage the feeding
function of the feed cylinder; thus the working fluid is
not significantly restrained in its passage between the
i~ cylinder and a storage reservoir or atmosphere. There will
be some resistance to fluid flow inherent in the system
2~ when the flow control valve is bypassed to l'disengage'l feed
cylinder 38; however, movement of the piston within
cylinder 38, as used herein, shall be deemed to be
"substantially unconstrained" when the working fluid
affords little or negligible resistance to arm movement.
As will be appreciated, it also is possible to
mechanically disengage cylinder 38 from arm or carriage 22
8~ '
; -14-
1 so that carriage movement is solely det~ermined by gravity.
Such a mechanically disenqaged feed cylinder also shall be
deemed to be "substantially disengaged" as used herein.
Moreover, it will be understood that for vertically movable
saw carriages, gravity will resist any upward movement o
carriage 22, whether mechanically disengaged or disengaged
by opening or effectively taking the flow control valve of
cylinder 38 out of the system. Still further, for
horizontally displaceable carriages a return energy means
such as a spring or pressure source is required to maintain
the saw carriage biased toward the work.
For purposes of simplicity of illustration. the
saw of Figure 1 has the wheel housings removed.
Additionally, it will be understood that guide assemblies
1533 and 34 are carried by arm 22, and the guide assemblies
twist blade ~9 from its horizontal orientation on the drive
and idler wheels tv substantially a vertical orientation
across cutting stretch 32.
As thus far described. the band saw apparatus is
well known in the prior art; vertical band saws as for
example shown in my United States Patent No. 4,117,756 and
horizontal band saws include unctionally equivalent
structure.
Band saw 21 further includes displacement or
2~ reciprocation means 41 formed and mounted to reciprocate
blade 29 toward and away from the workpiece during cutting
of the same.
~Broadly, blade displacement means are known in
;the prior art and not regarded as a novel portion o~ the
present invention. Saw blades, for example, having a
varying height dimension which pass over fixed rollers
. ,
1 effect displacement of the blade teeth relative to the
workpiece. Alternatively, the saw of United S~ates Patent
No. 4,127,045 employs a single reciprocation means; it is
mounted to a blade guide that is separated from the
workpiece being cut by a significant dis~ance (as shown in
the drawing, about one diameter of the workpiece).
Displacing the back edge of the saw blade at a single
location will effect see-sawing, but the effect is
minimized by bending or bowing of the blade between the
lQ guide and the workpiece. Hydraulic cylinder 52 constrains
the arm in the saw of United States Patent No. 4,127,045
against reaction, and the saw blade therefore flexes~ This
structure produces limited see-sawing on the entrance side
of the cut, but the exit side experiences only a slight
effect from bowing of the blade.
Additionally, the single point displacement
system of United States Patent No~ 4,127,045 also limits
the ability to superimpose independent and varying
frequencies and amplitudes of displacement at both sides of
the cut to achieve an optimum or tuned vibration pattern
for the particular material and shape being cut.
~ In the improved band saw apparatus o~ the present
i; invention, reciprocation means 41 is provided by two
relatively spaced-apart blade support assemblies, each of
which is formed and mounted for reciprocation toward and
away from the workpiece; this enables variation of the
angle of the cutting edge of the blade to increase the
cutting force per unit area of the localiæed pressure of
the blade against the workpiece.
As best may be seen in Figure 2 r reciprocation
means 41 on each blade support assembly preferably includes
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1 a blade support means or guide block 42 mounted for
engagement with the back edge 43 of saw blade 29. Blade
support means 42 further includes lever means 44 pivotally
mounted at 46 to an end of guide assembly 34. Coupled to
an opposite end of lever means 44 is a double-acting spool
valve or piston and cylinder, generally designated 47,
which may be pneumatically or hydraulically actuated. It
is preferable that blade guide block 42 be pivoted to lever
44 at 48, and that lever 44 actually be formed as a pair of
lever arms on either side of the central guide block 42.
The pair of arms can be pivoted at 49 to the end 51 of
movable piston element 52.
In order to twist the blade into a vertical
orientation, it is preferable that guide assemblies 33,34
further include a pair o~ guide blocks 53 which engage the
sides of blade 29. As shown in Figure 2, only one block 53
is visible, but it will be understood that a second half of
the lower guide assembly carrying a similar block 53 is
attached to the end of the guide by a fastener mounted into
a threaded bore.
Figure 3 corresponds to Figure ~ in that the
outside halves of the guide assemblies have been removed.
Figures 4 and 5 show the assemblies with the other half of
the ends of the guides secured in place so that a carbide
guide block 53 engages each side of blade 29t in a manner
well known in the art. The guide assemblies also
preferably include coolant channels 54 for the discharge of
fluid coolant down on the back edge 43 and sides of the
blade.
30Fluid piston-cylinder assembly 47 is operated by
communicating fluid ~hrough one of lines 56 and 57, e.g.,
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1 through line 56 to cylinder 58. In orde!r to control the
flow of fluid to cylinder 58, it is preflerable that flow
control valve S0 be positioned in one or both of lines 56
and 57. Valve 50 can be formed for controlled flow in one
direction and free flow in the opposite directionl or for
controlled flow in both directions.
The flow of fluid into cylinder 58 causes washer
or flange 59 (mounted on central longitudinally extending
shaft ~1) to be downwardly displaced, for example, by a
distance of 0.180 inches (4.5 millimeters), which in turn
causes backup guide 42 to move 0.060 inches (1.5
millimeters). When fluid is supplied in line 57 and
allowed to escape through line 56 past valve 50r cylinder
62 receives fluid and the flange and shaft are upwardly
displaced. The rate that the fluid volume enkers or leaves
cylinder 58 can be controlled by valve 50 so as to control
the speed of displacement and the duration of dwells, for
example, at maximum displacement.
; Lock nuts 63 and 64 can be used to easily vary
the amplitude of displacement. It will be seen that
displacement need not be very great in order to generate a
substantial displacement at cutting-edge 66 of the blade.
As will be readily understood~ the vertical displacement oE
the end 51 of shaft 61 is transmitted by lever 44 to guide
block~or blade enaging support 42. This in turn causes
displacement of the edge 43 of the blade, and a downward
displacement and a slight localized increase in pressure of
the cutting edge or teeth 66 against the workpiece.
In addition to displacement of the saw blade at
two spaced~apart locations along the length thereof to
maximize the see-sawing effect, it is a further very
.~ ' . .
.
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1 important feature of the apparatus and method of the
present invention that the saw arm or carriage 22 is free
or substantially unconstrained so that it can move toward
and away from the workpiece during blade displacement.
; In order to minimize deviation of the saw blade,
guides 33 and 34 should be positioned as close to workpiece
81 as possible. Such positioning of the blade guides
essentially eliminates ~minimizes) the flexure of blade 29
during displacement and/or see-sawing. To prevent "cligging
in" of the blade while still maintaining substantial
vertical displacement, the fluid control valve in fluid
feed cylinder 3~ is disengaged (in the "o~f" condition by
bypassing the valve as is explained in detail in connection
with Figure 93; descent o~ the arm is then controlled
solely by gravity (in vertically movable saws) and the
nominal resistance to fluid flow inherent in the cylinder
hydraulic or pneumatic system~
The result of freeing arm 22 from the constraint
of eed cylinder 38 is that displacement of the blade by
assemblies 41 urges the teeth into the workpiece beyond the
initial set required to pull a chip and until the teeth
start to dig in and stall the saw. As the teeth start to
; dig in, the resistance increases rapidly and forces arm 22
upwardly, even though displacement assemblies 41 are urging
the blade downwardly. The downward displacement of
assemblies 41 essentially causes the teeth to penetrate the
workpiece until the point of digging in is about to occur,
at which point further downward displacement is converted
to upward displacement of arm 22 against gravity.
Disconnecting feed cylinder 38 effectively permits the arm
to automatically move away from the workpiece or rebound
2S9351~
--lg--
1 just before digging in when the substantial increase in
load occurs.
Moreover, freeing the arm to move without the
constraint of the ~eed cylinder and associated control
circuit allows the arm to rapidly move back toward the
workpiece to maintain the cutting force on the workpiece
when the saw blade is displaced away from the workpiece.
Thus, the cutting Eorce is maintained at a substantially
constant level throughout a longer portion of the
reciprocation or blade displacement cycle. The result is
maintenance of the cutting force at a more constant level
closer to but below the level producing digging in and
stalling of the saw for substantially the entire
displacement cycle. This substantiall~ enhances cutting
efficiency.
As will be apparent, the inertia of the arm
affects rebound/ as will the area of the workpiece being
engaged and the hardness of the workpiece. The area of the
workpiece being engaged will also be effected by the amount
of see-sawing keduction of area) which is occuring and the
width dimension of the workpiece. For most commercially
available band saws, however, the inertia of the saw arm or
i movable frame or carriage will not be so great as to
prevent movement of the arm away before digging in of the
teeth,
Accordingly, for a given arm inertia and spaced-
apart displacement assemblies, the operator can tune
amplitude, frequency, displacement speed and duration of
any dwells in the displacement of the saw blade to cause
the teeth to penetrate the material up to a maximum short
of digging in, or for very hard materials up to a maximum
,
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1 for the inertia of the arm. The latter condition occurs
when the arm is very light or has a low inertia and it is
not possible to penetrate the teeth into the workpiece to a
degree approaching the dig in (stall or shear) point. Most
commercially available saws will have sufficient inertia to
5 cause the saw teeth to approach the dig in point and back
the arm up to release the blade short of diy in once the
amplitude, frequency and speed of displacement have been
tuned to the saw's physical characteristics.
In the preferred form, pivot 23 provides means
coupling arm or frame 2~ to the remainder of the saw for
advancement of the saw blade through the workpiece (or
through the portion of the workpiece being cut if the piece
is not to be cut completely through). When cylinder 38 is
disengaged, pivot means 23 for coupling the blade for
advancement is also coupled for free or substantially
unconstrained movement (pivoting~ toward or away from the
workpiece in response to relative displacement of the saw
blade away from and toward the workpiece. This enables
guide assemblies 41 to be positioned as closely proximate
opposite sides of the workpiece as can be accomplished
while still cutting to the desired depth in the workpiece~
As will be more fully described in connection
with Figure 9, the width dimension of many workpieces will
vary with the depth of cut. Most typical of such
workpieces is cylindrical bar stock. The effect of such
width variations is to change the area (length along the
b}ade) being engaged by the saw blade. When the area is
changing with the depth of cut, the automatic releasing
feature is very important. This feature disengages the
feed means for the saw so that the carriage can rebound or
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1 react away from the blade to avoid dig in and move toward
the blade to maintain the cutting force or pressure.
As the length of blade engagement with the
workpiece decreases, the force per unit area increases for
a given blade displacement. But, as digging in of the
5 teeth and stalling of the saw is approached, the carriage
moves away in reaction to the rapidly increasing
resistance. For narrow sections of the workpiece this
reaction away starts somewhat sooner as the smaller area
tends to result in digging in at an earlier stage. As the
section or width oE the workpiece increases, it takes more
displacement of the saw blade to reach the dig in point and
reaction away occurs later in the displacement cycle.
Freeing the saw from its ~eeding force, however, allows
automatic rebound before digging in even though the width
of the work is varying with the cut. The feed rate and the
displacement amplitude need not be set for the ~orst
(smallest area) condition in order to avoid dig in; instead
the feed is disengaged and amplitude of displacement
optimized with other operatiny conditions (e.g., blade
speed) to produce optimum cutting.
~ Displacement of blade 29 by a pair of spaced-
i~ apart blade guiding assemblies has several important
advantages over a single point displacement assembly of the
type disclosed in United States Patent No. 4,127,045.
First, as will be described in more detail
hereinafter, it enables very substantial changes in the
angle at which the workpiece is contacked during cutting.
Instead of pivoting around arm pivot point 23 or flexing
about one side of the workpiece, the two displacement
assemblies 41 can be run out of synchronism so as to rock
, ,
8~1
-22-
1 or see-saw the blade through angles which are much greater
than can be accomplished by a single point displacement
device for the ~ame amplitude of displacement. As the area
engaged by the teeth decreages~ the ability of the teeth to
approach maximum penetration short of digging in is
enhanced.
Second, each of the reciprocation assemblies 41
can be independently operated. Thus, it is possible to
superimpose different displacement frequencies and
amplitudes on top of each other, as well as operating the
displacement assemblies in synchronismO This allows the
user to tune or adjust displacement patterns until the
optimum for a particular workpiece and saw arm inertia is
achieved.
~ 15 Additionally, variation or increase and decrease
: in the area being cut by cutting edge 66 can be
accomplished at a frequency which is totally independent of
the shape or configuration of blade 290 Moreover, the
amplitude and rate or speed of displacement is also totally
independent of the shape or configuration of blade 29~
Still further, it is possible to vary the length of time or
duration at which the blade dwells at any of various
cutting angles with respect to the workpiece~
The independent variation of frequency,
2~ amplitude, speed of displacement and duration of the
dispIacement at two locations along the blade, when using
the apparatus of the present invention, has other important
advantages~
First, the band saw blade can be any standard or
conventional blade. Since there are many different types
of band saw blades (e.g. Raker set, wavy set, standard
~zs~
23-
1 tooth, hook tooth, skip tooth, and various tooth rakes),
one can achieve the benefits of blade vibration with
virtually any blade. Additionally, the ability to vary
frequency, amplitude, speed of displacement and duration
minimizes blade wear since the cutting force and large chip
load will be more evenly distributed over the length of the
blade.
Pneumatic and hydraulic valves 50 and controllers
are known in the art; they are capable of attachment to
fluid piston-cylinder assembly 47 to produce and vary the
frequency of fluid pulses to either side of the spool or
flange 59. In the preferred form, such controllers can be
; computer assisted with measurement apparatus (shown in
Figure 9).
; 15 Figure 9 shows a hinge-top or pivotal arm saw
with an angular transducer 136, but in a vertical or
horiæontal saw a linear transducer would be employed. The
main re~uirement is to measure or sense the position of the
saw blade into the material; then the controller would set
the cutting rate for optimi~ation of frequency, duration
and blade speed, all of which can be independently altered.
In the apparatus shown in the drawing, amplitude is
controlled by the lock nuts 63 and 64 and can be manually
altered, but it will be understood that more elaborate
apparatus Eor automatic controlled variation of amplitude
can also be incorporated into the fluid piston-cylinder
assembly 47.
An alternate emdodiment of fluid piston and
cylinder assembly 47 is shown in Figure 2A. Coupled
directly to a guide block (not shown), or indirectly
through a lever arm ~not shown)~ is piston rod 52a which is
....
1~5~88B
-24-
1 connected by fastener 55 to piston 59a. To produce a
reciprocal motion, piston 59a is biased by spring biasing
means 60 in a direction opposed to displacement produced by
introducing fluid into cylinder 65 through fluid conduit
56a and control valve 50a.
Again, fluid piston-cylinder assembly 47a enables
variation of the frequency, amplitude, speed and duration
of the displacement of the blade against the workpiece.
This is accomplished by controlling the fluid flow to
10cylinder 65 and piston 59a, against which spring 60 works.
In the preferred form of the invention, the
mechanical reciprocation of band saw blade 29 (see Fig. l)
is accomplished by blade support means mounted to a pair of
blade guide assemblies of the band saw.
15Reciprocation of blade support means also can be
accomplished, however, by displacing the entire arm 22
toward and away from the workpiece, either alone or in
combination with reciprocation at the guide assemblies.
Thus, arm displacement means, generally designated 71, may
be coupled to arm 22 for reciprocation of the arm toward
and away from the workpiece to enable variation o~ the
displacement of the cutting edge of the blade during
i~ advancement across the workpiece. In the preferred form of
this embodiment, a fluid piston-cylinder assembly 7~ can be
2S mounted in series with lift cylinder 38O Fluid piston-
cylinder 72 can be constructed substantially as shown in
conneckion with piston-cylinder assembly 47 and coupled by
conduit means 73 to a controller.
Disengaging ~eed cylinder 38 still ~rees the arm
3~ to rebound or move toward and away ~rom the workpiece as
necessary ko avoid dig-in of the te~th~ even though
1 cylinder 71 is used to displace the armn Alternatively,
displacement means 71 can be provicled with means, such as a
relief valve, for releasing or terminating downward
pressure if resistance from digging in of the teeth starts
to increase dramatically. Or, a balance cylinder can be
coupled to the arm in parallel to cylinder 38, as shown in
Figure 9.
The use of arm displacement means 71 to effect
mechanical vibration of the saw blade also allows a
variation of the frecluency, amplitude, speed and duration
o~ the vertical stroke of the blade independently of the
speed of advancement of the saw blade.
The improved cutting method of the present
invention, and the variations in cutting force per unit
area which can be achieved through the method and apparatus
of the present invention, are best described in detail by
reference to Figures 3 through 5~ One of the advan~ages of
vibrating or reciprocating blade support members 42 for the
saw blade is that two spaced-apart blade support members on
2~ the spaced-apart guide assemblies 41 can be used to see-saw
or oscillate the blade, as well as vertically reciprocate
the blade.
Oscillation of the blade can be accomplished by
operating the two stroke cylinders 47 out of phase. Thus,
as shown in Figure 3, the righthand lift cylinder and lever
44 are in an up position, as shown by arrow 74, while the
lefthand piston cylinder assembly 47 is in the down
; position, as shown by arrow 76~ The downward clisplacement
of the left side and upward displacement of the right side
causes the blade to lift upwardly by an angle C~.
-26-
; 1 In Figure 4, both stroke cylinders 47 are in a
neutral position, which can be an intermediate position
between the orientation of Figures 3 and 5 or illustrative
- of mid-stroke when the two stroke cylinders are
reciprocated in synchronism. Finally~ in Figure 57 the
positions of the cylinders of Figure 3 has been reversed
with the result that the angleo~ is now produced as an
! opposite or mirror image of that produced in Figure 3.
As will be understood, operation of cylinders 47
can be synchronized out o phase so as to produce a
constant oscillation of blade 29. In addition to
oscillating the blade, various complex reciprocation modes
can be employed. It is possible, for examplet to operate
one of stroke cylînders 47 at twice the frequency of the
other so that there are various in-phase and out-of-phase
displacements. It is also possible to hold one of the
cylinders in a neutral position while the other is
displaced down and then up, and thereafter to hold the
reciprocating one and displace the first one which was held
~ 20 through a stroke. To enhance control, the apparatus is
; shown with flow control valves 50 in both lines 56 and 57
Thus, it is a uery important feature of the
present invention that the mechanical reciprocation of the
band saw blade can be accomplished at at least two
distinct~ spaced-apart locations along the len~th of the
blade to enable oscillation, reciprocation and combinations
thereof. Using a computer to run the pneumatic controller,
it is readily possible to proqram very complex blade
reciprocation patterns to produce optimum cuttinq
efficiency~
~2~
1 An illustration of the method of the present
invention, and the advantages of the apparatus of the
present invention, can best be understood by reference to
Figures 6, 7 and 8.
As will be seen, a piece of round stock or
workpiece 81 of varying width is being cut by blade 29
using the apparatus of the present invention~ In order to
enhance the efficiency over the depth of cut, it is
preferable to change the blade displacement mode as a
function of the width being cut. In Figure 6, blade 29 is
generally horizontally oriented, and the stroke cylinders
are being operated in synchronism for essentially vertical
displacement as indicated by arrows 82. Such vertical
. reciprocation is continu~d until blade 29 has cut through
~ 15 approximately 10 to 20%, and preferably 15~, of the
: diameter of workpiece 81. Thus, when the width and area of
the workpiece are relatively small, see-sawing action is
not required.
Once the saw has cut through about 15~ of the
diameter, the stroke cylinders 47 are operated to cause
oscillation of blade 29 as indicated by arrows 83. This
oscillation results in a cut in which there are two beveled
i surfaces 84 and 86 against which the cutting edge 66 is
alternately cutting. The angles of these surfaces are
exaggerated in Figure 7 for he purpose of illustration;
they would normally be equal to the angle c~fro~ the
horizontal count as shown in Figures 3 and 5 or 2c~,
between cutting edge 66 and surface 86. The cutting is
continued in an oscillation mode until approximately 80 to
90% of the diameter has been cut; at this point the area of
the workpiece is again small and the cylinders are operated
8~3
-28-
1 in synchronism again, as shown in Figure 8 and indicated by
arrows 87.
As will be seen from Figure 7r the advantage of
oscillating is to reduce the length of surface being cut at
any one time during oscillation. ~hen round stock is being
cut, the effective cross section width can be reduced by
oscillation in the center of the cut. The outside edges of
round stock tend to have a lesser cross section in any
event and oscillation is not required. Eor square bar
stock, it is advantageous to start the cut without
oscillakting until the cut is established, and then to
oscillate the blade through the substantially entire cut as
a way of reducing the length of the blade in contact with
the workpiece during the cut. The cut is completed without
blade displacement (oscillation or reciprocation) to avoid
a sudden break-through of the thin section, digging in of
the teeth, and stalling of the saw (the last 5 percent or
less).
Referring to Figures 3, ~ and 5, it will be
apparent that a wavy back blade (U.S. Patent No. 4,195,543)
can be used to produce oscillation by simply allowing the
blade displacement piston-cylinder assemblies to be passive
(unpowered) or follow the back of the blade. Thus, if the
piston-cylinder assemblies 47 are connected together as a
clo~ed circuit, with conduits 56 coupled together and
conduits 57 coupled together (not shown) and valves 50
opened, the blade will have no vertical motion, or will
reciprocate, or will see-saw (oscillate), depending upon
the diskance bekween the wave peaks. If the guides are
spaced at one-half the blade phase, no vertical
displacement occurs. At a distance e~ual to the blade
-29-
1 phase, vertical displacement is produced. At distances
other than one-half or one blade pha~e, see-sawing results.
Thus, the apparatus of the present invention can be used
with conventional blades by employing powered blade
; displacement, or with variable height blades and employing
unpowered displacement.
Further alternative embodiments of the present
invention are illustrated in Figure 5A. Guide assembly 33a
is provided with an eccentrically mounted cylindrical guide
element or block 42a, which is formed for rolling
engagement with back edge 43 of blade 29. Advancement of
blade 29 produces rotation of block 42a about a shaft 40,
which is eccentric to the sur~ace of the block and which
causes vertical displacement of the saw blade.
~ 15 Guide assembly 34a includes a guide element 42b
; which has a planar blade engaging surface 30 formed for
sliding engagement with back edge 43 of the blade~ In
order to provide for reciprocation of blade 29, guide
element 42b includes an eccentrically mounted element 35
2Q formed for rotation about and driving by shaft 20. A
rotary motor (not shown~ drives shaft 20.
Each of guide assemblies 33a and 34a, therefore,
can be used in pairs of similarly formed assemblies and ln
various combinations with other blade displacing
assemblies.
An alternative embodiment of the band saw
apparatus of the present invention is shown in Figure 9.
Saw 112 is coupled to computer lllr which is preferably a
; general purpose digital computer~ to permit variation and
3~ optimum control of various operating parameters of the saw.
8~
-30-
1 As shown for the saw apparatus of Figure 1, saw
112 includes arm 113 pivotally mounted at 114 to saw base
115, and particularly arm support structure 116. Carried
by arm 113 are a pair of wheels 117 and 118 upon which saw
blade 11~ is mounted. The pivotally mounted arm thereby
provides a movable carriage means which can be displaced
toward or away from workpiece 123 by fluid piston-cylinder
assemblies 151 and 152 as will be described more fully
below.
In order to guide saw blade 119 as it cuts
workpiece 123, the saw further includes a pair of laterally
movable guide assemblies 121 and 122 which are mounted to
arm 113 by a track or guideway 133. Although it is
possible to provide one of guide assemblies 121 and 122 as
a fixed assembly, it is most preferable that both
assemblies are mounted for displacement along guideway 133,
as indicated by arrows 126.
As thus far described, saw 112 is constructed in
a manner well known in the art. The importance of
maintaining the saw blade guide assemblies as close to
workpiece 123 as possible in order to avoid blade wandering
also is well known. As above set forth, displacement of
the band saw blada has often been accommodated by
maintaininy the guides at a spaced dist~nce from the
workpiece to allow blade flexure with an attendant loss in
cutting accura~y. The method and apparatus of the present
invention permit blade displacement while the guides are in
~ close proximity to the workpiece by allowing the arm or
- carriage assembly to rebound. Accordingly, enhanced
cut~ing eEficiency can be accomplished without sacrificing
accuracy.
-31-
1 In order to further enhance the accuracy of band
saw cutting, saw 112 is formed for disp:Lacement of at least
one of guide assemblies 121 and 122 toward and away from
workpiece 123 during cutting. Thus, guide assembly
displacement means are provided for displacing one or both
of guides 121 and 122 relative to workpiece 123, which is
held by vise 124~
In the preferred form, guide displacement means
127 include motors 128 coupled to drive lead screws 129
which pass through a threaded bore in members 131. The
threaded members 131 are movably mounted with respect to
guideway 133 and are coupled to guide arms 132. When
actuated and controlled by computer 111, motors 128 can be
used to position the guide assemblies in substantially
abuttîng relation to workpiece 123.
Since workpiece 123 can vary in its width
dimension over the depth of cut, it is an important feature
of the band saw apparatus that guides 121 and 122 can also
vary in the width of their spacing over the depth of the
` 20 cut to better conform to the width of the workpiece and
thereby improve cutting accuracy. Computer 111 can be fed
a signal from sensing means so as to know the position of
blade 119 relative to material 123; in that way, the
position of guide assemblies 121 and 122 could be laterally
adjusted by computer commands to motors 128 for
displacement of guide arms 132.
Several methods of varying the positioning of
guide assemblies 121 and 122 to conform to the width of
workpiece 123 may be used. In a completely automated move,
the saw operator would input to the computer the bar stock
cross sectional configuration and nominal dimensions.
-32-
1 Alternatively/ sensing means and feedback to computer 111
can be employed, for example by sensors which determine the
pssition of vi e 124 when it grips workpiece 123. Standard
tracing methods, including sensors or a stylist mounted to
the guide arms which engage and follow irregular or varying
workpiece shapes, can be employed and ~ed back to computer
111 .
As shown in Figure 9, input signals from an
angular transducer 136 is fed back to computer 111 by
conductors 137. For vertical or horizontal saws, a linear
sensor or transducer would be substituted for angular
transducer 136. As arm 113 pivots, the computer receives
input as to the depth of th~ blade in the cut. If input is
also given that the workpiece is cylindrical bar stock, for
example, computer 111 can drive motors 128 (through
conductors 134) to position the guides next to workpiece
; 123 over the full depth of cut. Alternatively or
additionally, a cam and follower assemhly tnot shown) can
be positioned at pivot 114r with the cam having a surface
2~ which is angularly correlated to the width dimension at
various depths of cut for the workpiece.
Thus, sensing at pivot 114 or directly off the
workpiece can be used to control and vary the width of
guide assembly space during cutting It is most preferable
2S that guide assembly ends be relieved at 138 or relatively
small in height dimension to facilitate closer positioning
of the guide assemblies to workpiece 123 in the undercut
areas, such as the lower half of the cylinder.
As will also be seen from Figure 9, the lefthand
3~ lead screw 128 is longer than the righthand lead screw.
This structure is used because the lefthand jaw of vise 124
~33-
1 is usually adjustable while the righthand jaw is fixed.
Le~thand lead screw, therefore, accommodates the major
adjustments necessary for workpieces of various widths,
while both sides need only be adjusted to a more minor
degree to accommodate variation in the workpiece width as a
function of depth.
As will be apparent, the advantages of increased
accuracy are achieved by adjustment of the guide settings
as a function of workpiece width for saws which do not
include blade displacement means 141. But in combination
with the blade displacement means 141, both improved
cutting rates and improved cutting accuracy can be achieved
~ by moving guide assemblies 124 and 122 during cutting to
;~ maintain them as closely adjacent to workpiece 123 as
possible throughout the cut.
As shown in Figure 9, blade displacement means
141 are provided with fluid through conduits 143 connected
to a fluid controller, in this case pneumatic controller
145, which is connected in turn by conduit 140 t~ pressure
2~ source 1S7. Blade displacement is accomplished by levers
144, upon which guide blocks 146 are mounted and formed to
engage the back edge of blade 119, as described in detail
in connection with Figure 2.
In order to enable variation of the displacement
2~ Of blade 119 in combination with variation of other saw
operating conditions, pneumatic controller 145 is coupled
for control by conductors 150 to computer 111.
The feed and cutting force control means of saw
112 is provided by a pair of fluid piston-cylinders
assemblies 151 and 152, which are coupled to fluid control
circuits 153 and 154l respectively. The piston-cylillder
-34-
1 assemblies are pinned to arm 113 by pins 155 and to base
115 by pins 160 so that forces can be applied between the
base and arm to lift the arm and control its descent
Piston and cylinder assembly 151 and control
circuit 153 are used to lift the saw arm and to apply a
cutting force to arm 113 and thus blade 119. Piston--
cylinder assembly 151 is coupled between saw support or
base 115 and arm 113, and assembly 151 either supports the
arm with respect to the base or pulls the arm toward the
base to achieve the desired cutting pressure.
The pneumatic control circuit 153 preferably
includes a branch in which conduit 161 from pressure souce
157 has mounted therein a three-way lift valve 159 and a
two-way check valve 162. Upon opening of valve 159 by
15 solenoid 163 upon command from computer 111 through
conductors 164, the high pressure in conduit 161 drives the
ball 164 in valve 162 to the right seat and closes conduit
: 166 for the pressurization of conduit 167, conduit 168 and
- piston-cylinder assembly 151. High pressure in piston-
20 cylinder 151 raises arm 113 until the arm is topped by
ad~ustable stop means 169. Note that stop means 169 is
mounted on a rod 170 behind the piston rod 175 of piston-
cylinder 152. As will be appreciated, limit switches (not
shown) and/or angular transducer 136 can be used to signal
the computer to stop lifting of arm 113.
When the valve 159 shifts by solenoid 163, the
pressure source 157 is blocked, and that allows the
pressure in lines 167 and 16~ to flow back and leak to
atmosphere out of release or bleed orif ice 171 in valve
30 15~. Mounted in conduit 166 is a relieving regulator lS8
which can be set to relieve pressure in conduit 166 by a
-35-
: 1 valve actuator 172 ~oupled by electrical conductors 173 to
computer 111. When the pressure drops in 167 and 168 below
the pressure 5et in line 166 set by regulator 158, then the
ball 164 moves to the opposite side, and relieving
~ regulator 158 controls the pneumatic circuit.
; 5 In the example shown in Figure 9, the weight of
the arm is greater than the downward force desired to be
applied to blade 119. Control circuit 153, and
particularly relieving regulator 158, is set so that the
net of the pressure in line 166 and the weight o~ the arm
equals the downward cutting force applied to and throug
blade 119. Without more, arm 113 will descend slightly
until relieving regulator 158 has discharged gas through
outlet 1740 The weight of arm 113 is supported by the
combination of the preæsure in conduit 166 as determined by
regulator 158 and the predetermined force of workpiece 123
against blade 119.
; In order to enhance the accuracy of adjustment
and sensitivity of relieving regulator 158, it is
pre~erable to provide control circuit 153 with a conduit
176 having orifice means 177 mounted therein, with conduit
176 being coupled to pressure source 157 and conduit 167.
Orifice means 177 is a very small diameter orifice, e~g.,
0~004 inches (OoOll cm), in order to constantly leak
pressure into time conduit 167 which will be "seen" by
relieving regulator 158 when check valve ball 164 moves to
the left and opens conduit 166.
It is well known in the pneumatic art that the
leak provided by orifice 177 into the relieving regulator
will cause constant fwlctioning of the regulator and
thereby prevent ticking or delays and inconsistarlcy in the
~8
-36-
1 pressure relieving function. This portion of circuit 153
is not regarded as containing any novelty~
While piston-cylinder assembly 151 and control
circuit 153 provide control of the downward cutting force
applied by blade 119, piston-cylinder assembly 152 and
control circuit 154 provide for control of the advancement
of the arm and blade down through the workpiece.
As will be seen from Figure 9, it is preferable
that fluid circuit 154 be provided as a liquid control
circuit most preEerably employing oil 181 as the working
fluid. Fluid reservoir 182 is connected by conduit 183 to
four valves 184, 185, 186 and 187 and in turn through
conduit 188 to piston-cylinder assembly 152. Since circuit
154 is a closed circuit, when piston-fylinder 151 is used
to lift or raise arm 113 and if valve 184 is open, fluid is
drawn from reservoir 182 through valve 184 and past check
valve 186 and into cylinder 151 by suction.
Computer 111 is coupled by conductors 189 to
valve actuator 191 for variable or adjustable valve 185,
;- 20 and by conductors 175 to valve actuator 180 ~or variation; of the flow through valve 184. As the arm descends, check
valve 186 shuts and the working fluid returns to reservoir
lB2 through variable valve 185, which has been se by the
computer to control the return of fluid to the reservoir at
25 a predetermined rate. The computer can also shut off the
flow of fluid through valve 185 and stop the de~cent o~ the
- saw arm.
While fluid circuit 153 limits the weight or
force which can be applied to the blade, circuit 154
controls the rate of descent of the arm and blade.
~8
-37-
:
1 In order to enhance lifting of the arm and insure
flow of liquid to piston-cylinder assembly 152, ît is
further preferable to provide reservoir 182 as a pressure
vessel and couple penumatic conduit 168 to reservoir 182.
During the lif ting of arm 113 by pres urization of conduit
167, pressure through conduit 168 on reservoir 182 forces
oil up into the cylinder of assembly 1520 This pressurized
flow of oil to assembly 152 adds to the lifting force on
the arm and more positively insures that oil will fill the
cylinder than is the case when suction is the only
mechanism employed.
As above set Eorth, it is an important feature of
the present invention to be able to disengage or
essentially uncouple the feed portion of the saw when blade
119 is being displaced or reciprocated by displacement
means 141. Such disengagement frees the arm to rebound
toward and away from the workpiece as needed to enable the
a high, substantially constant, cutting force, ~s
determined by cylinder 151 and circuit 153, to be
maintained throughout the cutting cycle. In the fluid
control circuit 154 of Figure 9 this is accomplished by
providing valve 187 which can essentially dump to reservoir
182.
Solenoid valve operator 192 is coupled to
computer 111 by electrical conductors 193 to enable valve
187 to be selectively opened or closed by the computer. In
the closed position, fluid flows from cylinder 152 through
variable opening valve 185 as the arm descends. With valve
134 wide open, check valve 186 will permit rapid movement
of arm 113 away from the workpiece when the arm tries to
--38--
1 move upwardly away f rom workpiece 123 in response to
displacement of the blade toward the workpiece.
When valve 187 is opened~ however, the fluid
bypasses variable valves 185 and 184 and check valve 186
This allows the arm and saw blade to maintain the cuttiny
force of cylinder 151 when the blade displacement means 141
moves the blade away from the material being cut. The
fluid in circuit 154 is essentially free to move between
the reservoir and the cylinder as required by the dynamics
of vibrating the saw blade. Throughout this process,
relieving regulator 158 will maintain the pre-set cutting
force. Only the arm descent control will be disengaged.
It should be noted that when conduit 168 is
coupled to reservoir 182, the pressure in circuit 154 is
~also communicated back to circuit 153, so that a different
regulator setting is employed because both piston-cylinder
assemblies 151 and 152 pressurize conduits 167 and 166.
It is a further important feature of the present
invention to be able to change or vary the rebound rate of
arm 113 in one and preferably in two directions when the
blade displacement assembly in operating. Thus, instead of
simply dumping working fluid 181 back and forth between
reservoir 181 and cylinder 151~ it is preferable to provide
1Ow control means, such as valves 184 and 185, which can
be used to control or retard the movement of working fluid
181 as it moves between the reservoir and cylinder.
Computer 111, therefore, can be used to close
valve 187 so that flow back to reservoir 182 must pa~s
through valve 185. The computer can change the flow rate
setting of valve 185 from the feed rate to another rate,
usually a higher rate which is less than full open to the
,'' . '
-39-
1 reservoir. As thus controlled by the computer, the arm
will descend faster than the normal fe~d rate but slower
than when disengaged.
Similarly, valve 184 can be closed down by the
computer from a fully open position; this retards fluid
flow in the direction of cylinder 151 slightly, which in
turn retards the upward motion of the arm slightly. Such
computer adjustment oE flow control valves 184 and 185 can
be used to optimize or tune the arm reaction rate to
maximize the effectiveness of displacement of the blade by
assemblies 141.
Finally, compu~er 111 is preferably coupled to
control the speed of drive motor 196 t~rough conductors
197. As will be seen, therefore, computer 111 can be used
to control and vary: blade speed, blade displacement,
guide ass0mbly positioning, blade cutting force, and the
rate of blade descent and the reaction rate of th~ arm to
blade displacement. With this control, blade vibration and
oscillation can be controlled and optimized with other
operating parameters of the saw.
Angle transducer 136, for example, can be used to
give feedback to computer 111 to enable control of the feed
rate as a function of workpiece width, the positioning of
the guide assemblies as a function of width, and whether
the displacement means 141 are reciprocating the blade,
; oscillating the blade or not displacing the blade, all as a
function of workpiece width. Moreover, blade speed and the
cutting force can be coordinated with the other operating
parameters to maximiæe cutting efficiency and accuracy~
