Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BANI) SAW STRAIGE~TENING APPARATUS
F I ELD_OF_THE_I NVENT I ON
The invention relates to band saw straightening
appa~atus for the elimination of unevenness in band saw
blades with sensor controlled straightening rollers
disposed on opposite sides o~ the saw blade.
When ba~d saws are used for cutting wood,
u~eve~ness appearing on the saw blades can quite rapidly
assume such dimensions that such severely impairs the
eficiency and precision of the band saw. Band saw blades
therefore have to be straightened at regular intervals,
i.e. unevenness has to be eliminated. This has previously
usually been done by hand on a straightening bench using a
hammer against a flat steel anvil. This is a laborious and
lengthy procedure and, moreo~er, only produces relatively
imprecise results.
DESCRIPTION_OF_THE~ PRIOR_ART
; ~ German patent No. 33 13 160 describes a de~ice
intended to eliminate longitudinal and planar deformations
in band saw blades. This apparatus has rollers on both
sides of the saw blade which are so disposed in relation to
one another that the saw blade can be reshaped in a
direction opposite to that of the distortion. The roiler on
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one side is disposed in each case in the intermediate space
between two spaced rollers on the other side. To stretch
certain areas, individual pressure rollers are urged
towards each other so that the saw blade material lying
therebetween is distGrted by way of being stretched. This
device is used on the saw blade during cutting, with the
intended result that the saw blade does not need to be
removed from the saw. This device is not suitable for
dealing with the unevenness with which the present case is
particularly effective, i.e. bumpy distortions usually
limited to small areas and which are mainly caused by
sawdust accumulation during operation. French patent
2,229,492 discloses a saw blade straightening machine
having a pair of rollers of different rim width, the roller
having the larger width being located on the concave side
of the blade.
SUMMARY_OF THE_INVENTION
It is an object of the present invention to
provide a band saw straightening apparatus with which the
unevenness can be eliminated down to deviations of about
three hundreths of a millimeter. It is a further object of
the invention to provide an automatic band saw
straightening apparatus which does not require the full
attention of an operator.
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According to the present invention there i5
provided a band saw straightening machine for the removal of
unevenness in band saw blades comprising:
drive means for moving the blade;
a detector station including sensor means for the
detection of unevenness in a blade moving therethrough;
a straightening station including straightening means
for removing unevenness in a blade moving therethrough;
a measuring station including rate measuring means for
determining the rate of movement of the blade between the
detector station and the straightening station; and
control means for causing the straightening means to
function a controlled interval after the blade moves through
the detector station to act on the blade to straighten it.
Acco.rding to the present invention there is also
provided a band saw stra.ightening apparatus for removing
unevenness in band saw blades comprising:
straightening rollers disposed on both sides of the saw
blades for smoothing out uneven regions of the saw blade;
a measuring station for recording unevenness in the
blade, the measuring station comprising a flat pad for
engaging the saw blade and measuring means for sensing the
surface of the blade and generating a signal in response to
unevenness in the blade;
the straightening station comprising two pairs of
straightening rollers, one pair for leveling of upwardly
directed unevenness, and having a first roller with a convex
roller surface disposed at one face of the blade and a
second roller with concave rolling surface disposed opposite
the first roller, the other pair for leveling of downwardly
directed unevenness, and having a first roller with a
concave roller surace disposed at the one face of the
blade and a second roller with a convex rolling surface
disposed opposite the first roller of the other pair;
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the straightening station having means for pressing
the rollers against the blade;
drive means for advancing the sa~ blade; and control
means for correlating the sensing means with the
straightening rollers and the rate of movement of the blade
for pressing the rollers onto the saw blade at the
appropriate time when the unevenness has arrived.
Pre~erably, the second rollers are on ~ixed axles
and the first rollers are disposed on axles that are
movable toward and away from the blade for selectively
pressing the blade.
The means for pressing the rollers onto the saw
blade may comprise a pneumatic device and lever arms for
pressing the rollers.
Preferably, the control means is provided for
receiving the signals ~rom the measuring means and
selectively triggering the pressing action of the second
rollers.
According to the present invention there is also0 provided a band saw straightener comprising:
sensor means for detecting unevenness in a blade moving
therepast;
straightening means straddling a blade path and
cooperative with the sensor means for selectively pressing
a blade traveling therebetween to straighten sensed
unevenness in the blade;
drive means for advancing a blade in a blade path past
the sensor means and the straightening means,
the straightening means comprising rollers positioned
to straddle the passing blade and having complementary
shaped peripheral rolling surfaces;
the rollers comprising a first pair of blade
straddling rollers and a second pair of blade straddling
rollers;
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the first pair having complementary concave and convex
rolling surfaces and the second pair having complementary
- convex and concave rolling surfaces, with the first pair
concave rolling surface being at the same face of the blade
as the second pair convex rolling surface.
Preferably, the sensor means is upstream of the
straightening means; and
the straightening means is actuable to press the blade
in response to a predetermined amount of unevenness sensed
by the sensor means, to be actuated only when the sensor
means detects the predetermined amount of unevenness.
Other preferred embodiments and details are set
out in the following description of a preferred embodiment
of the invention.
BRIEF ~ESCRIPTION OF T~E DRAWINGS
.
Fiyure 1 is a perspective overall representation
of a preferred embodiment of a band saw straightening
apparatus of the inven-tion;
Figure 2 is a schematic representation of the
principle elements of the apparatus in Figure 1:
Figures 3A and 3B are enlarged representations of
the straightening rollers in side and end view respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 shows a band saw blade 1 inserted into
the novel apparatus. Viewing the apparatus from left to
right as shown in Figure 1, it has essentlally three
stations, a measuring station on the left hand side, a
straightening station 3 in the centre and a drive unit 4 on
the right hand side. The three functional units are
disposed on a rigid, massive stand 5 which is preferably of
welded sheet steel.
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Measuring station 2 has a table 6 under the saw
blade on which flat supporting rails 7 are disposed for
supporting the saw blade. The loading rails 7 consist of
hardened and ground steel in order to ensure a precision
base for measuring unevenness. Disposed above the saw blade
1 in the vicinity of each longitudinal edge of the band saw
are means to bias both edges of the blade against the
rails. These may be in the form of pairs of rollers 8 which
press the saw blade against supporting rails 7. For this
purpose rollers 8 are mountad on axles which may be
arranged on a lever system provided with weights 9. The
weights provide the biasing force. To insert and remove the
saw blade, rollers 8 can be lifted off the saw blade by
swinging i.e. pivoting the lever and weights.
A meas~lring gauge 10 is so disposed that its
feeler pin or other sensor rests on the surface of the saw
blade. The gauge is fixed to a shaft 11 which is mounted
transversely to the band and guides the measuring gauge 10
across the width of the band as needed. Shaft 11 may for
example be provided with a groove, so that the securing
block for the measuring gauge is slidably mounted on th~
shaft and is prevented from swiveling by means of a pin
running in the groove. Means e.g. mechanical, hydraulic,
pneumatic and/or electrical, are provided (not shown in the
figure) for thereby moving the measuring gauge transversely
across the width of the saw blade to selected positions on
the blade. As explained below, said means are adapted to
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move the sensor in synchronous manner with lateral moving
of the straightening rollers.
More specifically, the sensor and straightening
rollers can first be in one transverse position of the
blade, and then successively shifted to other transverse
positions until they ultimately move completely across the
width of the blade. Likewise, so that the straightening
rollers will be coordinated with this sensor, they will
simultaneously b~ moved to the same relative transverse
positions across the blade. The motive means to shift the
rollers may likewise be mechanical, hydraulic, pneumatic
and~or electrical. Thus, as the blade is longitudinally
advanced, a particular segment will be sensed to detect
deformation, i.e. unevenness, and acted upon as necessary
by the straightening rollers.
Behind and above the measuring station 2 is an
electronic control panel 12 shown disposed on a vertical
arm. On this control panel are set out the controls for
operation of the apparatus. They may, for example, include
control means and a corresponding indicating dial to
control the speed of passage of the band saw blade through
the apparatus, control means and a corresponding indicating
~ial to control the number of passes for each longitudinal
segment of the band saw blade prior to the feeler pin and
straightening rollers moving transversely relative to the
; blade to the next blade segment, and a series o indicator
and warniny lights representing various functions of the
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apparatus. The electronic control may also operate audibl~
alarms and a stop operation if necessary, e.g. in case of a
blockage.
An electric cable 13 leads from measuring gauge 10
to electric control panel 12. Via this cable 13, control
panel 12 receives a signal when the feeler pin or sensor of
the measuring gauge moves vertically beyond a given preset
tolerance, i.e. sensing a significant unevenness in a
portion of the blade. This tolerance can be preset at
control pan~l 12 at an amount of three hundredths of a
millimeter or some other amount.
Straightening station 3 is essentially grouped
around a central cast block 14. The cast block 14 can be
shifted along a shaft 15 transverse to the saw blade.
Shifting is effected by a threaded spindle 16 which engages
with a corresponding thread in the block 14 and is
rotationally driven by a geared motor (not shown). Shifting
transversely to the saw blade is effected in steps of, for
example 5 mm, and occurs in time intervals that correspond
to one or several passages of the saw blade as desired.
With this stepwise eed the straightening station is moved
and guided transversely across the saw blade in correlation
with the measuring gauge upstream thereof. The terms
upstream and downstream are intended to be descriptive
relatlve to the direction of movement of the blade.
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At the fror.t end of block 14 is disposed a irst
pair of rollers 18, 19 and a second pair of rollers 20, 21.
The second pair is downstream of the first pair, relative
to the direction of blade advancement. The four rollers 18
to 21 have a common central level or reference plane. The
rollers in each pair are vertically aligned with each
other. The first pair of rollers 18, 19 in the form
depicted serves to smooth out upwardly protruding
unevenness in the saw blade, while the second pair of
rollers 20, 21 as depicted serves to smooth out downwardly
protruding unevenness in the saw blade. The lower roller 19
of the first pair runs on a shaft 22 which is so disposed
that the roller 19 constantly engages the saw blade.
Similarly, the lower roller 21 of th~ second pair is so
disposed on a shaft that it continually engages the saw
blade. Upper roller 18 of the first pair is eccentrically
disposed on a shaft 23. In this manner roller 18 can be
removed from engagement with the saw blade, or pressed
thereagainst, by turning the shaft 23. To press roller 18
down, a pneumatic cylinder actuator 24 is linked via lever
25 to the shaft 23 to rotate it. A corresponding lever
system links up to a like shaft (not shown) on which
roller 20 is eccentrically secured and which is turned by
like pneumatic cylinder actuator 26.
- Drive unit 4 ~s mounted on a housing 27. This
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drive unit is downstream of the measuring station and the
straightening station to pull the blade through these
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latter stations. It has a drive roller 28 engaging the
blade and driven by an electric motor (not shown) or the
equivalent. The requisite pressing force is exerted by a
lever and a weight 30. In front of, i.e. upstream of, driv~
roller 28 is situated a measuring roller 29 which measures
by its rate of rotation the saw blade travel and transmits
information contimlously to control panel 12 regarding
blade speed, i.e. distance traveled by the blade in a glven
time.
Functioning of the apparatus may be seen with
reference to the simplified schematic representation set
out in Figure 2. Saw blade 1 is driven by drive roller 28
from left to right as shown in Figure 2. Straightening
apparatus 3 and the measuring gauge 10 are so situated that
the feeler pin or sensor o~ the measuring gauge lies in the
vertical mid plane of 18, 19, 20 and 21. This is positioned
at the longitudinal edge of the saw blade at the
commencement of the straightening process by the gear motor
which effects the lateral movement of the straightening
device. In this position of the measuring gauge and also
the straightening rollers, a track segment having a width
which corresponds to the width of the rollers is
straightened throughout the length of the saw blade. The
straightening procedure for one track segment can be
performed for just one passage or, i~ necessary in order to
remo~e difficult deformations, for ~everal passages of the
saw blade through the stations. The number of passages per
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track segment is preferably set by control panel 12, or can
be done manually.
When the measuring gauga locates unevenness lying
outside the preset threshold tolerance value, measuring
wheel 29 on the drive unit simultaneously records the
distance of blade travel from the measuring gauge to the
straightening rollers. Follo~ing expiry of the time
interval to travel this distance the controi unlt 12
transmits a signal to the straightening unit to cause one
of the two pneumatic cylinders 24 or 26 to press one of the
two upper rollers with a preset pressure against the
respective lower roller, by turning the corresponding
shaft. It the unevenness is an upwardly oriented bump, the
first roller 18 will be pressed down. If it is a
depression, the second roller 20 is pressed down.
The shape and formation of the rollers and their
function is shown in Figure 3A and 3B. Figure 3A shows a
qide view of the rollers 18, 19, 20, 21. Lying therebetween
is saw blade 1. It can be seen that th0 lower two rollers
19, 21 engage the saw blade. The two upper rollers 18, 20
are shown elevated a small distance from the saw blade. As
already mentioned, these are only pressed down when
required.
Figure 3B shows the rollers in end view. Roller 18
has a convex peripheral or rolling surface. Roller 19 lying
below it has a complementary concave peripheral rolling
surface of like configuration. When the upper roller is
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pressed down the saw blade portion is pressed by the
convexity of the upper roller into the like ~haped groove
or channel of the lower roller to level it. The more the
une~enness deviates or protrudes from the level plane of
one face of the blade, the greater the pressure and force
that the roller will tend to apply.
On the right hand side the action is reversed. The
upper roller has a concave roller surface. Lower roller 21
has a complementary convex peripheral roller sur~ace of
like shape. When upper roller 20 is pressed down, saw blade
1 is pressed by the convexity of lower roller 21 into the
concavity of upper roller 20 so that downwards facing
unevenness is evened out.
In a typical apparatus according to the invention,
the force exerted by the roller would be of the order of
600 kg. Other pressures may be employed depending on the
thickness, strength and quality of the saw blade and its
speed of movement. In one embodiment of the invention, the
blade may be driven at a speed of about 7,000 mm per
minute.
Unevenness is usually largely eliminated af~er
only one passage. Following several passages up to a
maximum normally of no more than 5 times, the saw blade can
again be described as being completely level. ~fter the one
or more selected number o passases for one track the
straightening rollers and the measuring gauge are shifted
transversely the amount of the roller width, e.g. ca. 5 mm
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so that th~ next track, i~e. blade portion can be smoothed
out. This continues through successive positions across the
blade width.
It has been found advantageous to provide a
certain degree of play in the threaded spindle which serves
to feed the straightening device transversely to the saw
blade so that when the procedure is e~fected in the
opposite direction, i.e. when the straightening device and
the measuring gauge are shifted transversely in reverse
there is an overlapping of the tracks. This is of
particular advantage i wider rollers are used, ~or example
10 mm, to process wider saw blades more quickly.
Certain variations in the component orientation
could be made without departiny from the invention. Thus,
the straightening roller pairs as shown could have rollers
18 and 19 downstream of rollers 20 and 21 so that the
upstream rollers would have the convex roller on the bottom
and the concave roller on top.
Also, in describing the preferred embodiment
herein, the blade has been shown and described to be in
horizontal orientation when being sensed. straightened and
driven. Thus the blade straddling rollers have been
described and shown as vertically above and below the
blade, with the upper rollers movable vertisally. Although
this is expected to be the most common orientation, the
invention is no~ intended to be limited by this terminology
or positioning since the blade could be in vertical cr even
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diagonal orientation when processed. The relative positions
of the sensor and rollers to the blade and to each other is
what is significant in this respect.
In view of variations which could be made in the
invention, it is intended that the invention is not to be
limited to the exemplary embodiment depicted and described
in detail, but only by the appended claims and the
reasonable equivalents thereto.
