Note: Descriptions are shown in the official language in which they were submitted.
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1 FIELD OF rHE INVENTION
The presen-t invention relates to a monitor for
determining and indicating performance of a bandsaw while
in operation.
BACKGROUND OF TH~ INVENTION
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According to conventional construction, bandsaws
include a cutting band or blade which is tensioned around
a pair of takeup rolls with an idler tension wheel and a
drive wheel for operation of the saw blade~ The drive
wheel which operates at variable selectable speeds
determines the blade speed which is one of the important
operating parameters of the cutting action of the
bandsaw. Two other operating parameters which are of
importance include feed rate of the blade or the speed at
which the blade is moved into the material to be cut în a
direction perpendicular to the teeth of the blade and the
cutting rate or the area of the cut per unit of time.
For example if it takes five minutes to cut through a ten
inch square block the feed rate is two inches per minute
and the cutting rate is twenty square inches per minute
as de-termined by multiplying the feed rate times the
width of the cut.
The cutting rate is extremely imPortant as it
determines the time it takes to cut through
cross-sections of various shapes and sizes. It is
therefore generally used in the saw machine and blade
using and manufacturing industries as the denominator -for
sawing performance under different conditions.
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1 The actual cutting rate achieved is lnfuenced for
example by the following factors: 1) the blade life
which can be expressed as -the total area (in sq.in.)
which can be cut with a blade while it gives a
satisfactory cutting performance or which may be
expressed as the total cutting time of a blade during
which it gives a satisfactory cutting performance;
2) the material of the blade teeth; 3) the shapes,
angles, distance between and number of blade teeth; 4)
the material to be cut; 5) the shapes and dimensions of
the material to be cut and 6) the design and rigidity of
the sawing machine and the blade guidance system on the
sawing machine.
As will be appreciated from the blade life factors
listed above it is not simple to arrive at cutting rate
figures which are correct for a wide range of
conditions. Accordingly the saw blade manufacturers
facilitate the proper setting of sawing machines for the
uses of their blades by recommending cutting rates for
certain conditions. Therefore the problem for the users
of the sawing machines which to date have no monitors for
determining cutting rates is how to set the machine to a
desired cutting rate or how to determine at what cutting
rate the machine is actually cutting. Conventionally the
cutting rate is determined by calculating the
cross-sectional area of the material and then using a
stop watch or timer to determine how long the actual cut
takes. The cutting rate is then calculated by dividing
the area of the cut by the time for the cut. This
procedure is obviously very cumbersome and for larger
material dimensions is extremely time consuming.
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1 Nearly all semi or Fully automatic saws are equipped
with a hydraulic saw feed system and the feed rate is set
by hydraulic valves with a graduated scale. The
graduation is however not expressed or graduated in
inches per minute feed rate since the actual feed rate is
not constant at one dial setting but rather varies
according to the viscosity of the hydraulic flu.id, the
pump, the filter conditions and gradual changes of the
control valve characteristics caused by deposits, etc.
Furthermore these feed rate indicators still require the
operater to divide the length of the cut by the feedrate
to calculate the time for the cut and to then calcuate
cutting rate as indicated above or to multiply the feed
rate by the width of the work piece being cut.
The foregoing problems have therefore lead to a
standard practice in the sawing industry where the
setting of the machines or saws is done according to the
individual judgement of the operators and where
supervisors and management do not control whether or to
what extent recommended and efficient cutting rates are
used.
SUMMARY OF_THE PRESENT INVENTION
The present invention relates to a bandsaw
performance monitor specifically adapted to mitigate the
control problems as found in the prior art by providing
simple and effective means for setting and controlling
bandsaw operations. The bandsaw per-formance monitor of
the present invention enables the setting of bandsaws
quickly and easily to maximize cutting performance and to
immediately monitor the actual useage and performance of
the saw and saw blade at all times.
1 More particularly the monitor of the present
invention which indicates and/or controls bandsaw cutting
parameters is characterized by an electronic feed rate
measuring system for measuring displacement of the
bandsaw blade in the feed direction, a selector system
settable to different shapes and sizes of cutting
profiles and a cutting rate measuring system including
display means for receiving information from both the
feed rate measuring and the selector system to measure
lû and indicate cutting rate as the area cut per unit of
time.
With this arrangement the operator of the machine is
at all times aware of the cutting rate of the machine.
BRIEF DISCUSSION OF THE DRAWINGS
The above as well as other advantages and features
of the present invention will be described in greater
detail according to the preferred embodiments of the
present invention in which:
Figure 1 is a plan view of a bandsaw incorporating a
cutting rate measuring system according to a preferred
embodiment of the present invention;
Figure 2 is a block diagram of the components within
the cutting rate measuring system.
DETAILED DE-SCRIP-rION ACCORDING TO THE PREFERRED EMBODIMENTS
Figure 1 shows a bandsaw comprising a stationary
frame F with a moveable carriage C carrying a bandsaw
blade B to cut into a work piece WP. The blade is
tensioned between a pair of rollers within the carriage
as shown in Figure 1 and driven by a drive system (not
3û shown) such that the blade rotates in a continuous
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1 fashion about -the rollers to perform a sawing action.
The carriage moves down relative to the ~Frame with the
blade in motion to cut downwardly into the work piece.
Two critical operating parameters of a bandsaw are
the feed rate or displacement of the bandsaw blade which
is the rate at which the band saw blade penetrates
downwardly into the work piece and the cutting rate which
is the area of the cut or the feed rate times the length
of the contact region between the bandsaw blade and the
work piece. In Figure 1 the workpiece has a rectangular
configuration but could however have other shapes such as
rounded configurations where the extent of the contact
between the bandsaw and the work piece increases with
depth of the cut. Therefore there are different cutting
profiles which are used in association with the depth of
the cut in determining the cutting rate.
Referring now to Figure 2, an electronic distance
measuring scale 1 is provided on the frame of the saw. A
scale sensor 2 is attached to and moves with the carriage
over the scale to sense degree of carriage and blade
downward movement.. The movement between the carriage
and the frame of the saw machine on which the electronic
scale 1 is provided is measured by distance pulses which
are transrnitted to two different measuring devices
including a feed rate counter 3 and a cutting rate system
4. The feed rate counter 3 consists of a conventional
frequency counter calibrated to show the speed of
movement between the carriage and the rnachine frame in
terms of inches per minute.
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1 Although the drawings show a linear scale it is also
possible to use a rotary pulse sender having For instance
a gear on its shaft which engages in a racl< to obtain the
required pulses for measuring downward movernent of the
carriage and the saw blade.
The cutting rate system is connected to a selector
system 5. This selector 5 changes the measuring or
calculating of the cutting rate system 4 in such a way
that the read out of the cutting rate systern reflects the
product of the feed rate and the contact region between
the saw blade and the work piece according to the profile
of the work piece to be cut. This selector system
changes correspondingly therefore the indicated values in
the cutting rate system 4 to reflect the product of the
feed rate and the contact region.
The rate meters may operate in a number of different
manners. According to one example the rate meters
consistent with fret~uency meters operate in a manner such
that the incoming pulses from the value to be measured
are counted for a certain time period. This time period
is selected such that the pulse count accumulated during
the time period corresponds directly to the value to be
indicated which is the rate per unit of time in seconds,
minutes, hours, etc. depending upon the particular type
unit to be expressed. However the number o r pulses per
unit of time has no direct relationship to the unit in
which the rate is commonly expressed. For example in the
arrangement shown a pulse sending system may for example
be used which furnishes 100 pulses per milimeter of
travel of the saw blade into the material. According to
1 this system a total of 2540 pulses enter the system for
every one inch of travel at the feed rate of one inch per
minute or in other words at the feed rate of one inch per
minute the system receives 2540 pulses every minute. If
a read out accuracy for every one hundreth of an inch is
desired and if the read out indicates 1.00 at the travel
speed of one inch per minute then the time base must be
selected such that during the period of the time base 100
pulses enter the measuring system. According to the
formula below, the time base to indicate a feed rate of
l.Oû per minute must be calculated as follows.
Therefore in order to set a read out accuracy of
l/lOOth of an inch the feed rate counter would be set
correspondingly at a time base of 2.36 seconds which
means that the counter would count lOû pulses every 2.36
seconds at the feed rate of one inch per minute.
For purposes of determining cutting rates the time
base may be varied according to the contact length
between the saw blade and the work piece. For instance
in the example above if the feed rate is one inch per
minute and the width of the cut is one inch then the
cutting rate is one square inch. ~lowever, if the width
of the cut is two inches and the time base is doubled
then the cutting rate indicated will show double the
number of pulses and this read out would then correspond
to a cutting rate of two square inches per minute at a
feed rate of one inch per minute. Correspondingly if the
w~dth of the cut is half an inch and the time base is cut
in half then the cutting rate would be .5 square inches
per minute. In this fashion the cutting rate can be
varied by changing the t:ime base to correspond to the
cutting width or contact length between the saw blade and
the material being cut.
This variability of the tirne base is achieved
through the selector system 5 shown in the drawings
whereby the cutting rate indicator rather than indicating
a feed rate shows a cutting rate and this example is in
terms of square inches per minute.
~ As will be seen, selector 5 is adapted to select
materials to be cut according to not only width which
would be used in a generally rectangular work piece but
also to select different diameters for rounded work
pieces where the multiplicatlon factor is determined
according to the diamete~ or circumference of the work
piece. For purposes of this description the width or
diameter is referred to as the profile of the cut.
The example described above is only one method of
determining cutting rates. According to a further
example it is possible to use a cutting rate indicator
consisting of a pulse frequency converter with selectable
frequency converting ratios. The converted frequencies
are then fed into a frequency counter which operates as
follows.
The frequency or rate counter would be set to a
standard time base of for example 1/100 of a minute or .6
seconds. It would therefore display the nurnber of pulses
entering the counter within this time period. The
electronic scale or scale sensor system which would
operate in the same manner as described above would
therefore furnish 2540 pulses at the speed of one inch
1 per minute. By selecting a cutting width of one inch the
cutting rate would then be one square inch per minute.
The feed rate counter would allow pulses to enter every
1/100 of a minute during which time 25.4 pulses would be
counted. The pulses however do not enter directly to the
feed rate counter but rather enter the pulse frequency
converter. This pulse frequency converter would be set
to the ratio of 2.54 to 1 whereby the 25.4 pulses
entering the converter would be displayed at the output
of the conver-ter to the reduced figure of 10 pulses
through the conversion factor. Therefore according to
this example the pulse frequency converter would as
mentioned above be set at a 2.54 to 1 ratio to make the
rate counter display the numeral 10 for a cutting rate of
one square inch per minute with the standard time base of
1/100 of a minute. The resolution of such an execution
is in l/lOths and the decimal point must be moved by one
point to the left -to provide the cutting rate correctly
resulting in the display of the numeral one rather than
the numeral ten.
If the width of the cut is increased to two inches
rather than one inch the read out value is doubled which
is achieved by changing the frequency conversion ratio
through selector 5 to 1.27 to 1 rather than 2.54 to 1.
This means that with the same feed rate of one inch per
minute but with double the cuttirlg width the pulse
frequency converter when set at the 1.27 to 1 ratio will
show 20 pulses entering the rate counter in 1/100 oF a
minute which is read out again with a resolution of 1/10
at 2.0 square inches per minute. The purpose for this
resolution is to keep the read out of the cutting rate as
simple as possible for operator examination purposes.
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1 In still another solution to the cutting rate system
design a digital programmable processiny unit is used to
operate as -Follows.
The feed rate is measured in a first operation of
the digital processor during a fixed time basis~ The
feed rate so obtained does not have to be directly
expressed in any meaningful ratio such as for example
inches per minute or millimeters per minute. It does
however have to be directly proportionate to the feed
rate of the saw blade regardless of the manner in which
it is expressed.
The feed rate value so obtained is processed in the
digital processing unit by multiplying the value with a
factor corresponding and directly proportionate to the
profile to be cut. The product of this multiplication is
then displayed at the rate indicator. In accordance with
the selection of different cutting profiles the digital
processor is controlled and set to the required
multiplication through the selector system 5 used by the
operator to input the width of the profile to be made.
In all the examples given above the time base
setting which in turn results in the setting of the
multiplication is done through settable binary digital
switches. For purposes of assisting in the setting of
the switches, setting tables may be provided which show
how the binary digital switches should be set for a given
width of rectangular cutting area or for diameters of
round bars as described above. Additional tables can
also be provided to show the code setting for tubes and
other special profiles.
1 In more sophisticated versions interfaces may be
provided between the binary digital switches and the
selector system allowing the selection of dimensions
directly in conventional units for widths and diameters
as they are used in the English and metric systems.
With the system described thus far, the sawing
machine operator pre selects the diameter or width of cut
on selector 5 and then adjusts the feed rate of the
bandsaw in such a way that the cutting rate read out
shows the recommended cutting rate for the material
concerned and the particular saw blade used. The
operator is therefore able to directly set the machine to
the data provided to him for his job or recommended by
the manufacturer of the saw blades usedO Supervisory
personnel can also constantly directly check whether the
process is carried out according to recommended cutting
rates.
The saw monitoring system can be further expanded to
furnish important information on how long the saw blade
being used ~ill remain in good operating condition to
furnish accurate cuts and to complete the cuts in
acceptable cutting time. According to this invention the
blade life may be controlled by the saw monitoring system
in three different ways. If for instance the cutting
rate measuring system uses a pulse frequency converter to
obtain a pulse output which is proportionate to the
cutting rate then this frequency converted pulse rate can
be fed into a blade li~e interface 6 and from there the
blade life counter 7. In the blade life interface the
pulses are converted into units which reflect directly
1 square inches with further control inputs from the
interface 6 to a saw feed circuit ~ and a saw motor
control circuit 9~ A logic control within the blade life
interface 6 allows the pulses from the cutting rate
system 4 which are proportionate to the cutting rate to
enter the blade li-fe counter 7 only if the saw motor is
operating and if the -forward saw feed is activated. The
blade life counter 7 is therefore operational only when
the saw is actually cutting but not when the saw frame is
moving forward during other manipulations of the machine.
The blade life counting system as described and
showing blade life in square inches in the counter 7 may
suffer however from the problem that the square inches
accumulated are incorrect if the selector 5 is wilfully
or accidentally set for a different profile other than
the one which is actually being cut. A practically more
reliable and simpler system is therefore one in which an
hour meter 10 is connected to the saw monitor circuit 9
in the saw feed circuit 8 in such a way that the hour
meter totals hours only when the saw motor is operating
with the saw feed forward engaged. Accordingly the hour
meter becomes a blade life counter showing blade life in
terms of hours.
In automatic machines it is also desirable to count
the number of cuts. This is achieved by using a counter
11 and connecting it in turn to the saw feed circuit in
such a way that it will be activated each time a
repetitive electrically controlled motion such as
clamping or engaging the saw feed forward is carried
~0 out. Again such a counting of pulses is achieved by
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a.~
1 connecting counter 11 with the saw motor circuit 9 so
that a count takes place only when the saw motor is
engaged.
In order to correctly reflect the total blade life
and the number of cuts made with the saw blade the two
different blade life counters 7 and 10 and the cut
counter 11 can only be reset by a key lock reset 12.
This reset will only be actuated by a key whenever the
blade is changed and a correct count for the saw blade
life cycle is obtained.
Other data important for control of the sawing
machine are the cutting time and the cycle time in
automatic machines. For this purpose two dif-ferent
counters including a cutting time counter 13 and a cycle
time counter 14 are connected with the electrical control
system of the sawing machine. The cutting time counter
13 will again only measure when the saw motor is engaged
and is connected to the saw feed control circuit in such
a way that it will only count time during the engaging of
the saw feed forward.
The cycle timer 14 will also only count when the saw
motor circuit 9 provides its signal showing the saw motor
is operating and the cycle timer will then measure the
time between repetitive sawing machine operations such as
engaging saw feed forward or engaging material clamping.
~ oth the cutting time counter 13 and the cycle time
counter 14 are preferraby of a type to measure each cycle
and to then display the measured value during a measuring
period of the next cycle so that the last measured time
cycle is displayed while the new cycle time is measured.
13
1 As a separate important operating pararneter a
complete execution of the saw monitor contains al~o a
blade speecl measuring device 15 which is connected to a
blade speed sensor 16 which senses the speed of the idle
wheel of the saw blade to obtain saw blade speed
proportionate pulses from the drive system for the saw
blade drive wheel.
In order to simplify the display system and to lower
the cost for the whole monitoring system it is possible
to feed the output of the measuring system for the blade
speed, for the feed rate 9 for the cutting rate, for the
c~tting time and for the cycle time into a selector
device 17 which is provided with five separate push
buttons for the five values and which depending upon its
selected position will feed only one of these five
para~eters into the read out. It is however also
pûssible to have individual read outs for the different
measuring systems although the one read out may be
advantageous from a cost standpoint.
It is also possible to connect the two different
blade read outs 7 and 10 and the number of cut read outs
11 to a single read out system with an expansion of the
read out selector switch 17. However from a control
standpoint it maybe more practical to display these
particular values constantly in separate counters which
are of a simple and space saving design.
The effectiveness and simplicity of application of
the monitor can be further improved by adjusting the
selector system of the cutting rate measuring system
automatically to the size oF the profile to be cut. This
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1 can be done by providing a size measuring system at the
saw which for instance measures automatically the
diameter of a round bar or the width of a rectangular
cross-section to be cut~ The measured value of the
workpiece is transferred into the selector system -for the
profile. This selector system requires then only a
setting to either round bar stock or retangular bar
stock. Only in cases of irregular profiles or tubes
would it be necessary to set the selector manually For
profile and dimensions of the workpiece. A typical size
measuring system 2 as shown, measures distance between
the clamping jaws J and Jl for the workpiece and
consists of an electronic measuring scale attached to one
jaw and the displacement sensor on the other jaw~ The
size measuring system is connected in turn to the
selector system as shown in Figure 2.
It will now be seen from the above that the
operating parameters of the bandsaw may be quickly and
easily discerned at any and all times of operation
through the monitoring system of the present invention.
Furthermore although various preferred embodiments of the
present invention have been described herein in detail it
will be appreciated by those skilled in the art that
variations may be made thereto without departing From the
spirit of the invention or the scope of the appended
claims.
