US20080218763A1 - Apparatus for optically determining the surface contour of flat workpieces in a wide belt abrading machine - Google Patents

Abstract

An elongated bar shaped housing contains an optical sensing apparatus with at least one light source to create a sensing beam and a deflecting arrangement which moves the sensing beam back and forth between the longitudinal ends of the housing. One of the walls of the housing has an output window extending in the longitudinal direction of the housing for the sensing beam and an input window parallel to the output window for the sensing beam reflected from a workpiece or its support. In the housing behind the input window there is a strip shaped light receiving arrangement with a plurality of optical sensors, as well as an evaluation unit connected to the light receiving arrangement to which the output signals of the light receiving arrangement are sent.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• Applicants hereby claim foreign priority benefits under 35 U.S.C. § 119 of German Patent Application No. 10 2006 012 941.5 filed Mar. 21, 2006 and German Patent Application (not yet known) filed Aug. 10, 2006, the disclosures of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
• 1. Technical Field
• The invention concerns an apparatus for optically determining the surface contour of flat workpieces in a wide belt abrading machine.
• 2. Background Art
• A belt abrading machine is known, from DE 32 02 104 A1, which has a presser bar extending transversely to the advancement direction of a workpiece and having a number of presser shoes arranged next to one another for pressing the abrading belt onto the upper surface of the workpiece. In it the pressing force of each presser shoe is individually controllable in dependency on the contours of the workpieces on a transport belt running under the abrading belt. For this the workpieces are sensed by means of detectors, for example non-contactingly by laser light fences. The detectors are arranged next to one another transversely to the transport direction of the workpieces, with each presser shoe of the presser bar having several detectors arranged in a row with it.
• The optical detectors allow a better resolution than mechanical scanner elements, are however expensive in their multiplicity, and under the operating conditions of an abrading machine are capable of being disturbed by the yielded abrasion dust.
SUMMARY OF THE INVENTION
• The invention has as its basic object the provision of an apparatus of the previously mentioned kind whereby with higher spatial resolution less expense is necessary and the apparatus is less capable of being disturbed.
• This object is solved in accordance with the invention by an elongated bar shaped housing containing an optical sensing apparatus with at least one light source to create a sensing beam and a deflecting arrangement which moves the sensing beam back and forth between the longitudinal ends of the housing, and in that one of the walls of the housing has an output window extending in the longitudinal direction of the housing for the sensing beam and an input window parallel to the output window for the sensing beam reflected from a workpiece or its support, with there being in the housing behind the input window a strip shaped light receiving arrangement with a plurality of optical sensors, as well as an evaluation unit connected to the light receiving arrangement to which the output signals of the light receiving arrangement are sent.
• In the solution of the invention the sensitive optical elements are given protection in the housing and thereby are protected against the environmental influences inside the abrading machine, especially against the penetration and depositing of abrasion dust. Dust cannot stick as easily to the flat windows of the housing. Moreover it is easier to clean said windows. At the same time by means of the roaming sensing beam the entire working width of the abrading machine can be continuously sensed, so that a high spatial resolution is possible, which is essentially limited only by the arrangement of the optical sensors.
• In practice the precision of the sensing can be disturbed by the widening of the sensing beam on its way from the deflecting device to the workpiece, by the diffusion of the light of the sensing beam and by the light reflection.
• These problems in a first embodiment can be solved in that the deflecting device includes a position sensor whose output signal contains information for determining the deflection direction of the sensing beam. If the deflecting device is made for example with a rotatable mirror, this mirror or its drive can be coupled to an angular position detector.
• According to a second embodiment the sensing beam has associated with it a reference beam which reference beam inside of the housing is directed onto a second strip shaped light receiver arrangement with a plurality of optical sensors and along which second strip the reference beam is deflected in synchronism with the sensing beam, with the output signals of both light receiving arrangements being transmitted to a common evaluation unit. The evaluation now proceeds in such way that the signal of the first light receiving arrangement, which is hit by the sensing beam, is only evaluated in regard to its relation to whether a workpiece is present at all. The second light receiving arrangement, which is hit by the reference beam deflected in synchronism with the sensing beam delivers the location information, that is where the workpiece has been sensed on its support surface. Since the reference beam extends only inside of the bar shaped housing and preferable from the deflecting device is directed immediately onto the second light receiving arrangement, this reference beam is not influenced by diffusion and other disturbances, so that its striking spot on the second light receiving arrangement can be essentially more precisely localized than it may be the case with the sensing beam on the first light receiving arrangement. By combining the two signals in the common evaluation unit a precise localizing of a workpiece on the supporting surface can result without being influenced at all by external disturbances.
• The sensing beam and the reference beam can be derived from a common light source. It is however, simpler and more disturbance free to create each of the sensing beam and reference beam from its own light source.
• To deflect the sensing beam and reference beam in synchronism with one another it is advantageous if the sensing beam and reference beam are deflected by the same deflecting device, for example by a rotatable mirror associated with both beams.
• Preferably arranged between the rotatable mirror and the output window is at least one stationary mirror which is so positioned that the deflected sensing beam escapes from the output window of the housing at a pregiven angle. This way one obtains larger freedom for the arrangement of the light sources and the deflecting device inside of the housing. The stationary mirror or one of the stationary mirrors is preferably adjustable so as to be able to adjust the output direction of the sensing beam from the output window.
• The light receiving arrangements are advantageously each made from a row of photoelectric elements which makes possible a very high spatial resolution.
• The invention concerns further an abrading machine, especially a wide belt abrading machine, with a workpiece support surface on which flat workpieces are transported in a transport direction through the abrading machine, with a circulating abrading belt running parallel to the transport direction and with a presser bar extending across the width of the abrading belt and having a number of presser elements independently controllable from one another by a control unit. Such wide belt abrading machines are known as such and need not be described in more detail. In accordance with the invention the abrading machine includes a previously described apparatus for optically determining the surface contour of flat workpieces, with the bar shaped housing upstream of the abrading belt extending transversely to the transport direction across the workpiece support surface with the output window and the input window turned toward the workpiece support surface, and with the evaluation unit being connected to the control unit so that the determined surface contour can be used in control signals for controlling the presser elements of the presser bar.
BRIEF DESCRIPTION OF THE DRAWINGS
• The following description in combination with the accompanying figures explains the invention by way of exemplary embodiments. The figures are:
• FIG.1—is a schematic illustration of a wide belt abrading machine with an apparatus for optically determining the surface contour of flat workpieces,
• FIG.2—is a schematic cross-section through the determining apparatus according to a first embodiment of the invention,
• FIG.3—is a schematic cross-section through the determining apparatus according to a second embodiment of the invention, and
• FIG.4—is a cross-section through the determining apparatus, and corresponding to that ofFIG. 3, according to a third embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
• The wide belt abrading machine ofFIG. 1 includes atransport belt10 forming the workpiece support surface on which aworkpiece12 can be transported in the direction of the arrow A. Above thetransport belt10 is arranged anabrading device14 with anabrasive belt16, which belt is guided over adrive roll18, aturning roll20 and atensioning roll21, and which belt in the viewing direction ofFIG. 1 extends transversely over the width of thetransport belt10. Theabrading device14 also includes apresser bar22, which in known way consists of a number of pressure elements or presser shoes which transversely of the transport direction A are arranged next to one another and by way of acontrol unit24 are individually and independently of one another controllable to press theabrading belt16 onto the surface of theworkpiece12 in accordance with its contour.
• To determine the contour of the workpiece and its position on thetransport belt10, ascanner bar26 is arranged upstream of theabrading device14, which scanner bar likewise extends transversely over the width of thetransport belt10, and whose construction and function will now be explained in more detail by way ofFIG. 2.
• FIG. 2 shows thescanner bar26 in a section perpendicular to thetransport belt10 and parallel to the transport direction A. Thescanner bar26 has a nearlycuboidal housing28 with abottom plate30 and acover bonnet32. Near the top surface of thebonnet32, inside of thehousing28 and at its middle in the longitudinal direction, is thelight source34 formed by a laser. Thelight source34 is associated with arotatable mirror36 driven by adrive38, so that thesensing beam40 emitted from thelight source34, at a frequency dependent on the number of facets of therotatable mirror36 and the rotational speed of thedrive38, is deflected along the length of thehousing28. Associated with therotatable mirror36 are twostationary mirrors42 and44 which are parallel to one another and which extend over the length of thehousing28. Themirrors42 and44 are faced toward one another and have such a spacing from one another that thesensing beam40 falling on therotatable mirror36 is reflected in several steps back and forth, as indicated inFIG. 2 by the zigzag beam path. Near thebottom plate30 is arranged anadjustable mirror46 which likewise extends over the entire length of thehousing28 and can be inclined about an axis48. It deflects thesensing beam40 through anoutput window50 in thebottom plate30. The output window is formed by aslot52 extending over the length of the bottom plate and covered by atransparent plate54 screw fastened to the bottom plate.
• Near the other longitudinal edge of thebottom plate30 is aninput window56 for the reflected sensing beam, whichwindow56 in the same way as theoutput window50 is formed by anelongated slot58 in the bottom plate covered by atransparent plate60 fastened by screws to the bottom plate. Behind the input opening is aphotodiode panel62 forming the light receiving arrangement.
• Thesensing beam40, with the help of theadjustable mirror46, is so deflected through theoutput window50 that it upon striking aworkpiece12 moves through theinput window56 and hits thephotodiodes64 of thephotodiode panel62, insofar as the thickness of theworkpiece12, by a certain tolerance, is not above or below a pregiven value. If on the other hand the sensing beam strikes thetransport belt10, that is the workpiece support surface, the beam reflected from it will not reach theslot58 and therefore will also not reach thephotodiode panel62, as is indicated by the broken lines. Therefore, the surface contour of theworkpiece12 and its position on the transport belt can be determined. Thephotodiode row62 is connected through anevaluation circuit66 with thecontrol unit24, which then based on the signals delivered by thephotodiode row62 or theevaluation circuit66 determines which segments of thepresser bar22 have to be controlled to press the abrasive belt in the desired way onto the upper surface of theworkpiece12. For this the signals received by the control unit from theevaluation circuit66 are amplified in the control unit in order to obtain the control signals for controlling the segments of the presser bar.
• Ascanner bar26 of the previously described type can also be arranged in the transport direction of the workpiece behind the abradingdevice14. Then the signals obtained from the evaluation circuit before their amplification can be evaluated as to their intensity. This provides information about the reflection properties of the workpiece top surface and allows, by comparison with reference values, statements to be made about the quality of the workpiece top surface or the wear of the abrading means.
• FIG. 3 shows a modified embodiment of the invention wherein parts corresponding to similar parts of the embodiment shown inFIG. 2 have been given the same reference numbers.
• Thesensing beam40 experiences in its path from therotatable mirror36 and via themirrors42,44 and46 a certain widening. Further the light of the sensing beam at the workpiece is dispersed and by light reflection is “contaminated”. This results in the light spot, which the light reflected from the workpiece creates on thephotodiode row62, being relatively wide, so that the location information is not so precise as it actually could be considering the construction of the photodiode row. This problem is solved by the embodiment according toFIG. 3 in that therotatable mirror36 or itsdrive38 is coupled to anangular position sensor65 whose output signal is transmitted to theevaluation circuit66 to deliver information as to the direction of thesensing beam40.
• In the modified embodiment according toFIG. 4, instead of the angular position sensor, in addition to thelight source34 which produces the sensing beam is a furtherlight source68 which produces areference beam70, which in the illustrated embodiment is directed parallel to the sensing beam created by thelight source34 and which is deflected by therotatable mirror36 synchronously with thesensing beam40. Thereference beam70 falls directly onto a second light receiving arrangement, which likewise is formed by aphotodiode panel72. Since thereference beam70 is subject to no disturbing influences, and from therotatable mirror36 falls onto thephotodiode panel72 without detour, it is still sharply bundled so that its strike location on thephotodiode panel72 can be precisely determined. Since thereference beam70 is deflected in synchronism with thesensing beam40, one from the reference beam can precisely determine the place where thesensing beam40 would have to hit thephotodiode panel62 if it were in sharply bundled condition and without external disturbances to reach thephotodiode panel62. In the evaluation circuit the signals of bothphotodiode rows62 and72 are evaluated. The signal of thephotodiode panel62 is evaluated only with regard to whether the sensing beam has struck a workpiece or not. The place where the workpiece has been struck by the sensing beam, that is where the workpiece is located on thetransport belt10, on the other hand is determined from the signals from thephotodiode row72 which is hit by thereference beam70. Therefore, the contour and the position of theworkpiece12 on thetransport belt10 can be determined with high spatial resolution and exactness entirely uninfluenced by external disturbances.
• It is further to be added that in the embodiments according toFIGS. 3 and 4 thebottom plate30 with individual windows has been replaced by atransparent bottom plate30. Also, onto the underside of thescanner bar26 is fastened by screws aram protection plate74, which serves to protect the scanner bar from blows from workpieces running from the right inFIG. 3 and which defines a limiting thickness of the workpiece. Further, this ram protector also serves to screen off reflections from the transport belt.
• While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention.

Claims (15)

1. An apparatus for optically determining the surface contour of flat workpieces in a wide belt abrading machine, characterized by an elongated bar shaped housing which contains an optical sensing apparatus with at least one light source for creating a sensing beam and a deflecting device which moves the sensing beam back and forth between the longitudinal ends of the housing, and in that in one of its side walls the housing has an output window extending longitudinally of the housing for the sensing beam and an input window parallel to the output window for the sensing beam as reflected from the workpiece or from the workpiece support surface, with a row shaped light receiving arrangement being located behind the input window within the housing and having a plurality of optical sensors, the output signals of which sensors are transmittable to an evaluation unit.

2. The apparatus according toclaim 1, wherein the deflecting device includes an angular position sensor whose output signal contains information for determining the deflection direction of the sensing beam.

3. The apparatus according toclaim 1, wherein the sensing beam has associated with it a reference beam which inside of the housing is directed to a second row shaped light receiving arrangement with a plurality of optical sensors and is deflected along the same by means of a deflecting device in synchronism with the sensing beam, with the output signals of the two light receiving arrangements being sendable to a common evaluation unit.

4. The apparatus according toclaim 3, wherein the sensing beam and the reference beam are derived from a common light source.

5. The apparatus according toclaim 1, wherein for the creation of the sensing beam and of the reference beam a separate light source is respectively provided for each beam.

6. The apparatus according toclaim 3, wherein each light source is a laser.

7. The apparatus according toclaim 3, wherein the sensing beam and the reference beam are deflectable by the same deflecting device.

8. The apparatus according toclaim 1, wherein each deflecting device includes a rotatable mirror.

9. The apparatus according toclaim 3, wherein the reference beam from the deflecting device is directed immediately onto the second light receiving arrangement.

10. The apparatus according to claims,claim 2, wherein the rotatable mirror or its drive is coupled to an angular position detector.

11. The apparatus according toclaim 1 wherein between the deflecting device and the output window is at least one stationary mirror so positioned that the sensing beam as reflected by it is deflected at a predetermined angle through the output window.

12. The apparatus according toclaim 11, wherein the stationary mirror is adjustable to change the output angle of the sensing beam.

13. The apparatus according toclaim 1 wherein the light receiving arrangements are each formed by a row of photoelectric elements.

14. An abrading machine with a workpiece support surface on which flat workpieces are transportable in a transport direction (A) through the abrading machine, a circulating abrading belt parallel to the transport direction, and a presser bar extending transversely to the transport direction across the width of the abrading belt with a plurality of presser elements which by way of a control unit are controllable independently of one another, characterized by an apparatus accordingclaim 1 with the bar shaped housing upstream of the abrading belt extending transversely of the transport direction across the workpiece support surface with the output window and the input window turned toward the workpiece support surface, and with the evaluation unit being connected to the control unit.

15. A method for examining the results of abrasion in the abrading of flat workpieces in an abrading machine, especially in wide belt abrading machines, in which method the abraded workpiece upper surface has at least one light beam deflected over it and the intensity of that beam as reflected from the workpiece upper surface is determined, and in which method said determined intensity values are compared with reference values.

Images