Circular saw blade straightening machine

A circular saw blade straightening machine for eliminating unevenness in circular saw blades is disclosed, having straightening rollers disposed on both sides of the saw blade. The rollers are disposed opposite one another on a straight line passing through the middle of the saw blade. A feeler gauge is provided to scan the surface of the saw blade and to generate a signal in the event of unevenness being detected to initiate an appropriate movement of the straightening rollers.

BACKGROUND OF THE INVENTION 
The invention relates to a circular saw blade straightening machine, for 
eliminating unevenness in circular saw blades, having straightening 
rollers disposed on both sides of the saw blade for evening out uneven 
areas of the saw blade. 
When circular saws are used in wood processing, unevenness develop in the 
saw blades which can be of such an extent after only a few hours' working 
time that the efficiency of the circular saw is severely impaired. 
Circular saw blades therefore have to be straightened at regular 
intervals, i.e. unevenness has to be eliminated. This has hitherto 
generally been done by hand on a straightening bench, unevenness being 
removed from the saw blade using a hammer on a planar steel plate. This 
was a very strenuous and laborious job and also led to relatively uneven 
results. 
DESCRIPTION OF PRIOR ART 
U.S. Pat. No. 510,210 discloses a device which serves to eliminate 
deformations on saw blades for circular saws. This machine has rollers or 
blocks on both sides of the saw blade which are disposed in relation to 
one another in such a way that the saw blade can be deformed in a 
direction opposite to that of the distortion. 
U.S. Pat. No. 4,852,430 discloses a band saw blade straightening machine 
with sensor means for scanning the surface of the blade and for generating 
a signal in the event of unevenness in the saw blade and a straightening 
station with two pairs of straightening rollers as well as means for 
pressing the rollers against the saw blade. The straightening rollers 
comprise two pairs of rollers, one pair of which has a roller disposed 
above the band having a convex roller surface for smoothing upwards 
directed unevenness and a roller with a concave rolling surface disposed 
opposite it under the band, the other pair for smoothing downwards 
directed unevenness having a roller disposed above the band having a 
concave rolling surface and a roller with convex rolling surface disposed 
under the band. The two pairs of rollers are disposed immediately behind 
one another and behind the dial gauge so that a straight line of the saw 
blade is straightened on each passage. 
This straightening machine is, however, unsuitable for circular saw blades 
because it is not possible to define straight pathways for the arrangement 
of straightening rollers and a sensor behind each other on a circular saw 
blade. 
OBJECTS OF INVENTION 
It is an object of the invention to provide a circular saw blade 
straightening machine which can be used to eliminate the above-mentioned 
unevenness down to deviations from the plane of three-hundredths of a 
millimeter. Fully automatic operation should, moreover, be possible, to 
dispense with the need for an operator. 
BRIEF SUMMARY OF INVENTION 
The instant invention accordingly provides a circular saw blade 
straightening machine having straightening rollers or drums for smoothing 
unevenness present on both sides of the saw blade and situated on a 
straight line passing through the middle of the saw blade and situated at 
distances substantially equal from the middle disposed opposite each other 
and a feeler gauge for scanning the surface of the saw blade and for 
generating a signal in the event of unevenness provided at the same 
distance from the middle of the saw blade offset at a particular angle to 
the straightening rollers. 
According to a further embodiment of the invention, the rollers arranged 
both above and below the saw blade are mounted on radially moveable axles 
and may thus be either pressed against or lifted off the saw blade. In 
this way, saw blades having cut-away portions, slits or extensions, etc., 
can also be straightened. 
According to a preferred embodiment the rollers disposed under the saw 
blade are disposed on fixed axles and the rollers disposed above the band 
are disposed on axles which are moveable so as to exert pressure. 
According to another embodiment of the invention the means for pressing the 
rollers against the saw blade or lifting them off the saw blade consist of 
a pneumatic or hydraulic device and lever arms. 
An electronic control unit is preferably provided which receives the 
signals from the dial gauge and the signals emitted by the drive unit 
concerning the band feed and processes these into an output signal which 
initiates the pressing or lifting off process. 
According to a further preferred embodiment of the invention, an additional 
pair of rollers is provided, in addition to the straightening rollers, 
whereby both the upper as well as the lower rollers have a slightly convex 
curved surface lateral to the direction of travel of the saw blade. This 
additional pair of rollers serves to set up circles of stress which impart 
tension to the saw blade. 
Various embodiments of the invention will now be described in a 
non-limiting manner with respect to the accompanying drawings.

DETAILED DESCRIPTION PREFERRED EMBODIMENTS OF THE INVENTION 
A circular blade 1 is mounted on a vertically disposed axle 3 using a 
securing nut 2. The axle 3 is fitted in the horizontal cover plate 4 of a 
housing 5 and driven by a drive motor 6 which is fitted in the housing 
under the cover plate. Also connected to the axle 3 is an incremental 
transmitter 7 which supplies electrical signals at specific angular 
positions of the axle. 
Disposed on the cover plate 4 are a straightening station 8 for smoothing 
downwards facing unevenness in the saw blade 1, a second straightening 
station for smoothing upwards facing unevenness in the saw blade 1, a 
measuring station 10 and a control unit 11 which will be described in more 
detail below. The straightening stations are disposed exactly opposite one 
another in relation to the axle 3 or, in other words offset to one another 
by 180 degrees. The measuring station 10 is preferably located at the same 
angle from both straightening stations, i.e. it is offset thereto by 90 
degrees. 
The straightening station 8 has a frame 12 in which is lodged an axle 13 
for a straightening roller or drum 14 disposed above the saw blade. The 
straightening drum 14 is eccentrically lodged on the axle 13 in such a way 
that it is normally at a small distance from the saw blade and that the 
drum is pressed against the saw blade when the axle turns. A pneumatic 
cylinder 16 associated via a lever 15 with the other end of the axle 13 
and controlled by signals from the measuring station serves to rotate the 
axle 13. 
A second roller or drum 17 which also rests against the saw blade is 
disposed under the saw blade in the frame 12. This serves as an abutment 
against which the saw blade is pressed when the upper drum 14 exerts 
pressure on the saw blade. 
The frame 12 is slidably guided on a rail 18 firmly fixed to the housing 
and arranged radially to the saw blade. A threaded spindle 19 disposed 
parallel to the rail 18 which is rotated by a drive 20 and which meshes 
with an internally threaded block 21 associated with the frame causes the 
displacement of the frame with the straightening rollers radially to the 
saw blade. 
The second straightening station 9 is similarly constructed. The measuring 
station also has a frame 22 radially slidable in relation to the saw 
blade, which is displaced in similar manner by means of a threaded spindle 
25 guided by a threaded block 23 disposed on the frame 23 and turned by a 
drive assembly 24. A dial gauge 26 having a sensor pin 27 resting against 
the saw blade is located on the frame above the saw blade. The drives for 
the threaded spindles are adapted to one another in such a manner that the 
sensor pin 27 and the middle planes of the four straightening rollers are 
always located on the same circular line or circumference within the saw 
blade. 
It can also be advantageous to provide a further adjustable supporting 
point for the saw blade whose level can be finely adjusted. 
The electronic control 11 is disposed above the measuring station on a 
swivel arm on a vertical arm. This electronic control unit will not be 
described here in detail since the function which it has to fulfil can 
readily be executed by a person skilled in the art using an appropriate 
circuit. 
An electrical lead connects the dial gauge 26 to the electronic control 
unit 11. This lead provides the control unit 11 with a signal when the 
sensor pin 27 of the dial gauge 26 is extended out beyond a given 
predetermined value. This value can be set in the control unit 11 and is 
three hundredths of a millimeter in the present embodiment. 
The shape and design of the rollers and their function may be seen in FIG. 
2. It will be seen that the two lower rollers 17, 17' are in contact with 
the saw blade. The two upper rollers 14, 14' are at a small distance from 
the saw blade. As already mentioned, they are only pressed downwards when 
necessary. The roller 14 has a convex running or rolling surface. The 
roller 17 lying therebelow has a concave rolling surface. When the upper 
roller is pressed downwards the saw blade is pressed into the channel or 
groove of the lower roller by the curvature of the upper roller. In this 
case the greater the unevenness deviates from the planar state, the 
greater the resulting pressure. The situation is reversed on the right 
hand side of FIG. 2. The upper roller 14' has a concave roller surface, 
the lower roller 17' has a convex roller surface. If the upper roller 14' 
is pressed downwards, the saw blade 1 is pressed into the groove of the 
upper roller 20 by the curvature of the lower roller so as to even out any 
downwards directed unevenness. 
Larger unevenness is already eliminated after one passage of one track. 
After several passages up to a maximum of five, the saw blade can once 
again be considered to be totally planar. After the selected number of 
passages for one track the straightening rollers and the dial gauge are 
displaced by the roller width of about 5 mm so that the next track can be 
treated. 
It has been found advantageous to provide a certain amount of play in the 
case of the threaded spindles serving to advance the straightening device 
radially to the saw blade so that the tracks overlap when the process 
occurs in the opposite direction, i.e. when the straightening device and 
the dial gauge travel back again. This is particularly advantageous when 
wider rollers are used, for example 10 mm, in order to process larger saw 
blades more quickly. 
Overlapping of the tracks can, however, also be adjusted in appropriate 
steps using stepping motors for the thread drive. The method of operation 
of the machine may clearly be seen from the appended drawings The saw 
blade is driven by the drive motor 6 so that it runs, for example, 
clockwise. The straightening stations 8 and 9 and the dial gauge 10 are 
positioned so that the sensor pin 27, the dial gauge 26 and the mid points 
of the rollers lie on the same circular path around the saw blade. At the 
beginning of the straightening process working begins with the smallest 
circle, i.e. close to the axle 3, because that is where the zero level of 
the saw blade is set. The straightening process for one track may take one 
passage or several passages of the saw blade. The number of passages per 
track is set from the control unit 12. 
When the dial gauge encounters an unevenness beyond the preset limit value, 
the timespan corresponding to the distance from the dial gauge to the 
straightening rollers is determined with the aid of the incremental 
transmitter 7. After the expiry of this period of time, the control unit 
11 gives a signal to the straightening unit which presses one of the two 
pneumatic cylinders against the saw blade at a preset pressure by rotating 
the corresponding shaft of one of the two upper rollers. If the unevenness 
was an upwards facing bump, the first roller is pressed downwards. If it 
was a depression, the second roller is pressed downwards. 
The above-described embodiment of the invention is suitable for the 
treatment of circular saw blades which have a planar flat surface with no 
interruptions. Apart from such circular saw blades there are also others 
which have cut-away portions, such as for example slits, holes, etc., or 
elevated portions such as for example wider cutters. During the treatment 
of such circular saw blades, the feeler gauge would recognize such 
cut-away portions or elevated portions as unevenness which needed to be 
straightened out and would give appropriate signals to the straightening 
rollers. This would initiate an inappropriate straightening operation. 
To avoid this, in a further embodiment of the invention an apparatus is 
provided for the detection of cut-away portions and means are provided for 
lifting the straightening rollers arranged on both sides of the circular 
saw blades. The measuring feeler gauge is also provided with two 
photoelectric cells which are arranged opposite each other adjacent the 
feeler. They are disposed in a radial plane with respect to the circular 
saw blade. Their distance from one another is for example 5 to 10 mm more 
than the width of the rollers. 
The photoelectric cells each consist of a light source disposed above the 
circular saw blade and a detector located thereunder. If the circular saw 
blades being treated have cut-away portions which are detected by the 
photoelectric cells, the control unit gives an impulse to lift the rollers 
according to an appropriate angular distance. 
In the case of cut-away portions in the circular saw blades and above all 
of the elevated portions mainly encountered at the edges of slits, such as 
wider cutters, both the upper and the lower rollers have to be lifted from 
the circular saw blades to prevent damage. For this purpose, in the 
embodiment for treating circular saw blades with cut-away portions and/or 
elevated portions the straightening rollers running underneath the blades 
are mounted on moveable axles just as the others are. These axles are 
moveable in a manner basically similar to that of the axles 13 so that the 
straightening rollers can be pressed against the circular saw blades or 
lifted away therefrom. 
The dial gauge or other measuring feeler gauge 26 is also modified for 
circular saw blades with cut-away portions and/or elevated portions. 
Instead of the sensor pin 27 a ball for example 10 mm in diameter is 
provided which "falls" into a cut-away portion without becoming damaged 
and which can be lifted again at the following edge. The ball also rolls 
over elevated portions without difficulty. The downwards movement of the 
ball is advantageously restricted by a stop. 
The impulse given by the control unit to lift the rollers is interrupted 
for the time taken for a cut-away portion to pass between the rollers. The 
straightening process continues normally thereafter. 
Another embodiment of the invention has additional means for rolling a 
desired tension into the circular saw blades. This procedure is known per 
se and has been conducted on equipment specially intended for this purpose 
As schematically shown in the plan view in FIG. 3, another roller 28 is 
disposed above the blade next to the straightening roller 14. This is 
mounted on a moveable axle 29 that lies parallel to the axle 13 and in 
principle similar thereto. Below the blade is an identically similar 
roller (not shown) which is also mounted on a correspondingly moveable 
axle. The roller 28 and its counterpart on the underside have a very 
weakly convex curvature transverse to the direction of travel. 
In place of one pair of tensioning rollers 28 it is also possible to 
provide two pairs in each case next to the two pairs of straightening 
rollers. 
These two tensioning rollers or tensioning roller pairs must, as in the 
case of the straightening rollers, be disposed in such a manner to the 
circular saw blade during operation that the axle 29 lies in a radial 
plan. To ensure this, means are provided with which the tensioned circular 
saw blade together with its drive can be shifted by the distance between 
the rollers 14 and 28, as indicated by the broken circular line. The means 
for shifting the blade are not shown since they can be manufactured 
without mechanical difficulties by a person skilled in the art. Using 
these additional rollers, the opposing pressure that they direct against 
the blade running therebetween flattens one or several circular tracks in 
such a manner that the blade is tensioned.