Abstract:
In order to obtain a simple, inexpensive and low-maintenance monitoring device for controlling the setting width of individual teeth of saw blades or belt-saw blades, in particular for controlling the setting result of a setting machine the present invention invisages that the monitoring device comprises at least one photo-detector whose light beam at least partly runs through one or both regions laterally next to the running-past saw blade or belt-saw blade, into said regions the set teeth project.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a device for monitoring and controlling the setting width of individual teeth of saw blades or belt-saw blades, and in particular for controlling the width of the setting made by a setting machine. 
     German Patent DE 195 17 482 A1 teaches determination of the deviation between an actual setting and a nominal setting via monitoring which does not make physical contact (e.g., opto-electronically). 
     Typically, opto-electronic monitoring is achieved by line cameras which monitor and record the actual width. If there is a deviation between the actual setting width and a nominal setting width, an automatic correction of the setting machine is made. These cameras are disadvantageous because they are expensive and sensitive to contamination. The cameras must precisely and accurately focus on the region where the actual width is found. Therefore, a considerable maintenance expense arises from adjusting and monitoring of the focus and from the regular cleaning of the camera. Otherwise unusable results are obtained. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a device for monitoring and controlling the setting width of individual teeth of saw blades or belt-saw blades, which operates reliably with the least amount of maintenance and manufacturing costs. 
     The object of the invention is achieved in that the monitoring device comprises at least one photo sensor which emits a light beam at least partly through a monitored region, adjacent to the running saw blade or belt-saw blade, where the set teeth  2  project laterally. Photo sensors are inexpensive to obtain and adjust, as compared to line cameras. A narrow parallel light beam between the light emitter and a light receiver allows the monitored region to be monitored with precise and accurate focus. Because the present invention does not use a lens like line cameras do, there is less chance of contamination, and the maintenance expense that is associated with line cameras is therefore reduced. 
     Although generally one photo sensor would be sufficient to monitor both sides of the saw blade, by for example using a mirror, a preferred embodiment of the invention includes two photo sensors for monitoring adjacent monitored regions on both sides of the saw blade or belt-saw blade. 
     The photo sensor may also comprise a laser, which obtains a sharply limited parallel light beam that is well suited for the monitoring of the setting made. 
     In a further embodiment of the invention, the photo sensor may be designed as a laser scanner, i.e. a light emitter and light receiver are rigidly connected by way of a U-shaped bow. 
     Such a laser scanner may be assembled on a laterally traversable and fixable carriage in order to be able to simply and safely emit the light beam precisely onto the region to be monitored. 
     The light beam is preferably emitted at a small angle with respect to the plane of the saw blade or belt-saw blade because an arrangement where the light beam is emitted parallel to the plane of a blade is subject to false or erroneous measurement if there is a backing of the saw or lateral deflection of the saw. If the backing of the saw is caused by a problem with the advancement of the saw, and is laterally deflected, the saw may not be within the region of the light beam. There is however no significant difference with respect to optical conditions between a light beam emitted at a small angle with respect to the plane of the blade and a light beam emitted parallel to the plane of the blade. 
     In another embodiment of the invention, the cross section of the light beam effective for the monitoring is dimensioned and arranged in a manner such that it essentially encompasses half the belt-saw blade body and the maximum setting width. The region between the middle position of the set tooth and the belt-saw blade body may be monitored, and even corrected if necessary, by way of the light beam that overlaps the belt-saw blade. 
     Centering is required for a reliable determination of the setting width. In order to ensure centering, a centering device is provided which centers the advancing belt-saw blade with respect to the photo sensors. 
     The centering device comprises two laterally adjacent jaws which are movably guided perpendicular to the saw blade plane and which are elastically pressed onto the belt-saw blade body in order to guide the belt-saw blade. A mechanical synchronization of a movement of the two jaws in opposite directions is further provided. In this manner the elastically mounted jaws may continuously laterally yield should the thickness of the belt-saw blade change or other lateral forces occur by way of disorder, such as for example by the waviness of the belt-saw blade. It is however always guaranteed that the jaws in each case are displaced by the same path distance, one to the right and the other to the left, so that a thicker belt-saw blade is always led symmetrically to a middle plane lying between the jaws. The jaws in each case are connected to a rack, and the teeth of the rack are in engagement with opposite sides of a pinion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a side view of a part of a saw blade; 
     FIG. 2 is a top plan view of FIG. 1 of the same saw blade; 
     FIG. 3 is a schematic representation of a monitoring device according to the invention; and 
     FIG. 4 is a schematic representation of a centering device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a belt-saw blade  1  which is provided for use in belt-saw blade saws. The belt-saw blade  1  has teeth  2  which are arranged on a belt-saw blade body  5 . Teeth  2  and blade body  5  are designed as one piece. The setting of bi-metal belt-saw blades is also possible. Along a line  3 , the teeth  2 , as also shown in FIG. 2, are laterally bent out of the plane of the belt-saw blade body  5  to the front and to the rear, so that there arises two groups of teeth, specifically a tooth group  2   a  which is bent to one side of the belt-saw blade  1 , and a tooth group  2   b  which is bent to the other side of the belt-saw blade  1 . The tooth groups  2   a  and  2   b  define a setting width indicated by way of the lines  4   a  and  4   b.    
     The setting is normally carried out in an automatic setting machine, wherein the actual setting width may deviate from the nominal setting width. Since the proper functioning of the belt-saw blade is dependent on the setting width, the setting result must be monitored and any deviations from the nominal value must be automatically corrected. In this invention an alarm may be triggered to indicate a deviation. 
     A monitoring device  6 , schematically represented in FIG. 3, is provided for monitoring the resulting width from the setting of the teeth. The monitoring device  6  comprises two photo sensors  7 ,  8  which in each case have a light emitter S and a light receiver E arranged opposite the light emitter S. The light emitter S consists of two lasers from which laser beams  9 ,  10  proceed which meet in the respectively allocated light receiver E. In the middle of FIG. 3, a belt-saw blade  1  is provided in a direction B as indicated in FIGS. 1 and 2. The belt-saw blade body  5  is centered with respect to a middle plane by way of a centering device described further below, wherein the teeth  2   a  and  2   b  project laterally to the left and right respectively. 
     The two laser beams  9 ,  10  are arranged in a manner such that they irradiate the two adjacent regions on the right and left sides of the belt-saw blade  1  into which the set teeth  2   a  and  2   b  laterally project. Laser beam  9  is provided for monitoring the teeth projecting out to the right and laser beam  10  for monitoring the teeth  2   a  projecting out to the left. Preferably the photo sensors, having a light emitter S and a light receiver E, are designed as laser scanners wherein the laser serves as a light emitter on the one side and a light receiver on the other side and the emitter and receiver are connected to one another by a U-shaped bow and thus are adjusted and fixed in their relative position to one another. 
     The laser scanners are preferably in turn mounted on a carriage which is not shown, so that each photo sensor is displaceable as a unit in the arrow direction  12  and after adjusting the respective laser beam  9 ,  10  are fixable onto the region to be monitored. 
     The belt-saw blade  1  for checking the setting result is transported in the advance direction  13  (see FIG. 1) through the monitoring device. In order to avoid errors in measuring, resulting from lateral movements of the belt-saw blade body  5  into the region of a laser beam  9 ,  10  the laser beams are not arranged parallel to the belt-saw blade body  5  and middle plane  11 , but at a small angle  14  with respect to the middle plane  11 . Furthermore the cross sections of the laser beams  9 ,  10  are dimensioned such that apart from overlapping the maximum setting width  4   a ,  4   b  they also approximately overlap half the thickness of the belt-saw blade body  5 . Therefore, the relative position of the belt-saw blade body  5  to the middle plane may be optically recorded and evaluated, since at the moment when the respective laser beam  9  emits through the gap between two teeth  2   a  and  2   b  it is still only partly shadowed by the section of the belt-saw blade body which projects into the region of the laser beam  9  and  10 . 
     Signals are emitted from the light receivers and are led to electronic evaluation devices via measuring conduits  15 . Electronic evaluation devices preferably consist of a programmable microprocessor. When there are deviations of the actual setting width from the predetermined nominal setting width, a signal can be emitted via a signal conduit  17 . Either an alarm may be triggered or a correction may be made in the setting machine automatically. The same applies for a deviation of the belt-saw blade body  5  from the middle position defined by the middle plane  11 . 
     In order to hold the belt-saw blade body  5  centered, a centering device is provided, as shown in FIG.  4 . This centering device consists of two centering jaws  18 ,  19  which each have associated parallel guides  20 ,  21 , that are movably guided perpendicular to the saw blade plane or to the middle plane  11  in the arrow direction  12 , and are elastically pressed onto the belt-saw blade body  5  of the belt-saw blade via two pneumatic pressing devices  22 ,  23  in order to guide the belt-saw blade  1 . In order to ensure that the belt-saw blade  1  is always guided symmetrically to the middle plane  11  the movement of the two centering jaws  18 ,  19  in the arrow direction  12  is synchronized in opposite directions. The two centering jaws  18 ,  19  are connected to a rack  24 ,  25 , wherein the respective teeth of the racks bear on opposite sides of a pinion  26  and are in engagement with the teeth of the pinion. When centering jaw  18  is moved the other centering jaw  19  is forced into an opposite movement so that the belt-saw blade  1  is always guided symmetrically to the middle plane, even with changes of the belt-saw blade thickness.