Patent Publication Number: US-2022212300-A1

Title: Apparatus for Supporting a Workpiece for a Plurality of Supporting Pins Which are Oriented Parallel and are Individually Longitudinally Movable

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application PCT/EP2020/077379 with an international filing date of Sep. 30, 2020 and claiming priority to German Patent Application No. DE 10 2019 126 361.1 entitled “Vorrichtung zum Abstützen eines Werkstücks mit einer Mehrzahl von parallel ausgerichteten and einzeln längsbeweglichen Stützstiften”, filed on Sep. 30, 2019. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an apparatus for supporting a workpiece with a plurality of supporting pins which are oriented parallel and are individually longitudinally movable. The workpiece supported by such an apparatus may rest on the supporting pins or it may be clamped by means of the supporting pins against a similar or a different apparatus. Thus, the apparatus may be used as a so-called form chuck jaw. In combination with a similar or a different apparatus, the apparatus is also suitable for grabbing applications, i.e. particularly for forming a grabber adapting or already adapted to the respective workpiece. 
     BACKGROUND OF THE INVENTION 
     A holding device for workpieces, which is known from German patent application publication DE 198 02 320 A1 and U.S. Pat. No. 5,988,618 belonging to the same patent family, comprises a fixing device for fixing the supporting pins with respect to the frame. On the back sides of the supporting pins facing away from the workpiece, an open pressure chamber is provided that can be pressurized with pressurized air which can exit the pressure chamber towards the respective workpiece through free spaces between the supporting pins. The supporting pins may have a radial shoulder within the pressure chamber so that the pressurized medium loads the supporting pins towards the workpiece. In order to determine a relative position of the respective workpiece with respect to the frames by means of one of the supporting pins, a microswitch is arranged between a retainer plate which delimits the pressure chamber and through which a retainer rod passes through, that is screwed from the back into a main body of the supporting pin such that the radial shoulder is formed. The microswitch is operated by a collar at the free end of the retainer rod when the supporting pin is pressed into the frame to a certain extent. Instead of the microswitch, a position encoder may be provided which determines the exact relative position of the supporting pin with respect to the frame. 
     A handling device for mechanically gripping, holding, moving and handling of objects of any shape, which is known from German patent application publication DE 43 39 102 A1 and U.S. Pat. No. 5,688,013 belonging to the same patent family, essentially consists of a high number of holding pins to be lowered onto the objects to be grabbed, which are mounted in bore holes in a holding pin guiding plate such that they can be moved longitudinally, and which clamp the objects. By pushing the holding pins back by means of an ejector plate, the objects are released. At the holding pin guiding plate, a light barrier is arranged which outputs a signal as soon as the holding pins are longitudinally shifted with respect to the holding pin guiding plate and get into a beam path of the light barrier with their upper ends. 
     An apparatus for flexibly grabbing objects comprising a sensor is known from U.S. Pat. No. 5,608,206. The sensor has a plurality of holding pins for contacting and grabbing the objects. The holding pins are mounted within a mounting plate in a longitudinally moveable way. The holding pins engage into a sensor array by which a relative shift of the holding pins with respect to the mounting plate is optomechanically coded and registered. At a back end of each holding pin, a hollow cylinder provided with openings is arranged, into which light is axially radiated by means of an optical fiber. Ends of other optical fibers punctually face the outer circumference of the hollow cylinder such that, in different longitudinal positions of the respective holding rod and the hollow cylinder connected thereto, light out of the hollow cylinder enters into the ends of different combinations of the other optical fibers. There still is a need of an apparatus for supporting a workpiece which is configured for a simple but extensive survey of its function such that an integration of the apparatus into fully automatic production installations is possible, that allow for a completely monitored and documented production. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an apparatus for supporting a workpiece. The apparatus comprises a frame and a plurality of supporting pins. Each supporting pin has an end face and a main extension direction. The supporting pins of the plurality of supporting pins are guided parallel to one another in their main extension directions in the frame. Each supporting pins of the plurality of supporting pins can be pushed-in against a restoring force with respect to the frame. A supporting field for the workpiece is made of the end faces of the supporting pins of the plurality of supporting pins. The apparatus further comprises a detection device including a light barrier configured to detect relative positions of at least some of the supporting pins of the plurality of supporting pins with respect to the frame. The light barrier has a light source and a light sensor, which face each other across the main extension directions of the at least some of the supporting pins of the plurality of supporting pins. Along one side of the supporting field, the light source is divided into a plurality of sub-sources, and, along another side of the supporting field facing the one side of the supporting field, the light sensor is divided into a plurality of sub-sensors. 
     Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and the detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic sectional view of an apparatus according to the invention for supporting a workpiece. 
         FIG. 2  is a plan view on a supporting field of the apparatus according to  FIG. 1 . 
         FIG. 3  shows an arrangement of sub-sources of a light source and sub-sensors of a light sensor of a light barrier of the apparatus according to  FIG. 1  in a first embodiment. 
         FIG. 4  shows an arrangement of sub-sources of the light source and sub-sensors of the light sensor of the light barrier of the apparatus according to  FIG. 1  in a second embodiment, and 
         FIG. 5  shows a further arrangement of sub-sources of the light source and sub-sensors of the light sensor of the light barrier of a further apparatus according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In an apparatus for supporting a workpiece comprising a frame and a supporting field made of end faces of a plurality of supporting pins which are guided parallel to one another in their main extension directions in the frame and which can each be pushed-in against a restoring force with respect to the frame, a detection device comprises a light barrier to detect relative positions of supporting pins of the plurality with respect to the frame. A light source and a light sensor of the light barrier are facing each other across the main extension directions of the supporting pins of the plurality. Along one side of the supporting field, the light source is divided into a plurality of sub-sources and, along another side of the supporting field facing the one side, the light sensor is divided into a plurality of sub-sensors. 
     With a suitable arrangement of the light source and the light sensor in the main extension directions and with regard to the main extension directions, it can be detected with the light barrier whether the supporting pins of the plurality, which are at least some and preferably all supporting pins of the plurality, are pressed-in with respect to the frame or not. Particularly suited for this purpose is an arrangement of the light source and the light sensor in which the not pressed-in supporting pins of the plurality are not in the light path of the light barrier between its light source and its light sensor, but get into this light path when being pressed-in and then block the light coming from the light source in front of the light sensor. The apparatus may detect a relative reduction of a light intensity presently registered by the light sensor of the light barrier with respect to a maximum intensity with free light path between the light source and the light sensor. This means that the apparatus does not only detect whether any or a certain minimum reduction of the light intensity is present. The relative reduction of the light intensity indicates to which extent the light path between the light source and the light sensor is blocked and thus how far the supporting pins and/or how many of the supporting pins of the plurality are pressed-in with respect to the frame. 
     Whether a certain relative reduction of the light intensity indicates a regular or a faulty function of the apparatus depends on the actual use of the apparatus. If the apparatus, for example, presently supports a workpiece, wherein the supporting pins are partially pressed-in with respect to the frame to adapt to a surface of the workpiece, a certain relative reduction of the light intensity registered by the light sensor is an indication of a regular function. If, however, the supporting pins are unloaded, so that they should be reset by the restoring forces with respect to the frame, any reduction of the registered light intensity is an indication of a failure. It is to be understood that the reduction of the registered light intensity is not mandatorily resulting from a pressed-in supporting pin. It may also result from the entry of contamination into the area of the light barrier. This is also be regarded as a failure of the apparatus. 
     As the light source of the light barrier of the apparatus is divided into a plurality of sub-sources along one side of the supporting field and the light sensor of the light barrier is subdivided into a plurality of sub-sensors along another side of the supporting field facing the one side, the light intensity detected for the light of the individual sub-sources and the sub-intensities detected by the individual sub-sensors allow for a spatial localization of the supporting pins pushed-in with respect to the frame. At best, it can be resolved which exact supporting pins within the supporting field are concerned. Practically, in this embodiment of the apparatus, a line array of sub-sources on the one side and a line array of sub-sensors on the other side of the supporting field may be used which are available as parts of low-cost commercial light barriers. 
     It is to be understood that it may even more accurately be determined where and which supporting pins are pressed-in with respect to the frame, if the light source is divided into a plurality of light sources along several adjoining sides of the supporting field, and the light sensor is divided into a plurality of sub-sensors along several other sides of the supporting field facing said several sides. 
     Practically, one sub-source and one sub-sensor of the light source may be assigned to each line and to each column of supporting pins of the supporting field. 
     Additionally, the light source may also be divided in several sub-sub-sources in the main extension directions of the supporting pins and the light sensor may be divided into several sub-sub-sensors in the main extension directions of the supporting pins. Then, it can be even more accurately resolved how far the supporting pins of the plurality are pushed-in with respect to the frame. 
     In order to obtain maximum information with regard to the positions of the individual supporting pins with respect to the frames with a light barrier having a light source including several sub-sources, the detection device may individually activate the sub-sources and separately detect the light intensities registered by the individual sub-sensors for the individually activated sub-sources. From the pattern of the registered light intensities, a related press-in pattern of the supporting pins may be deduced via a table of empirical values, or it may at least be acknowledged whether a press-in pattern of the supporting pins, which should actually be present, is in fact present or not. 
     Typically, the apparatus also has a fixing device by which the supporting pins can be fixed with respect to the frame. Thus, a certain press-in pattern of the supporting pins may be fixed by means of this fixing device. The detection device of the apparatus preferably activates the light barrier at least then, when the fixing device is deactivated to reset to supporting pins by means of their restoring forces. Then, the light source detects whether this resetting of the supporting pins actually took place or whether individual supporting pins have not been reset which indicates a failure. 
     In a practical embodiment of the apparatus, the supporting pins, with their ends facing away from the end faces, immerge into a chamber which can be pressurized with a pressure medium. Then, the detection device may be configured to especially activate the light barrier then, when the chamber is pressurized with the pressure medium and, if present, a fixing device is deactivated. Under these operating conditions, not only the restoring forces onto the supporting pins should be provided by means of the pressure medium, but also any contaminations between the supporting pins should be blown out of the pressure chamber and the free spaces between the supporting pins by means of the pressure medium. Correspondingly, the light path of the light barrier should be free. If, nevertheless, there is a reduction of the light intensity registered by the light sensor, this reduction indicates a failure. 
     In the apparatus, the detection device is preferably configured in such a way, i.e. a controller of the detection device is programmed in such a way, that the detection device automatically evaluates the light intensity registered by the light sensor of the light barrier for failure indications and outputs a failure signal, if a failure indication is present. It is even more preferred, if the detection device indicates a probable failure source and/or failure removal option by means of the error signal. In this way, valuable indications are given to the user of the apparatus. It is to be understood that the failure signal from the detection device of the apparatus may be used in an automatic production installation to stop the production installation to avoid a faulty production. 
     Referring now in greater detail to the drawings, the apparatus  1  depicted in  FIG. 1  serves for supporting a workpiece which is not depicted here. For supporting the workpiece, the apparatus  1  comprises a supporting field  2  of end faces  3  of a plurality of supporting pins  4 . Along a part of their length, the supporting pins  4  are enclosed by a frame  5  and guided parallel to one another in their main extension directions  6 . In the main extension directions  6 , the supporting pins  4  can be pressed-in against restoring forces with respect to the frame  5 . The restoring forces are primarily provided by pressure springs  7  which are arranged on retainer rods  8 . The retainer rods  8  which pass through a retainer plate  9  are screwed into the back ends  10  of main bodies  22  of the supporting pins  4 . The pressure springs  7  are supported at the ends  10  at their one ends and at the retainer plate  9  at their other ends. Heads  11  with enlarged diameter of the retainer rods  8  abut against the back side of the retainer plate  9  and thus retain the supporting pins  4  at the retainer plate  9 . A chamber  12  is formed between the ends  10  of the main bodies  22  and the retainer plate  9 . The chamber  12  can be pressurized with pressurized air  13  from a pressurized air source  14  to apply additional restoring forces onto the supporting pins  4  (or even to replace the pressure springs  7 ) and to blow contaminations out of the free spaces between the supporting pins  4  which are of circular cross sections. By means of a fixing device  15  the supporting pins  4  can be fixed to the frame  5 . Here, the fixing device  15  comprises a screw drive  16  which acts upon a pressure plate  17  that is movable with respect to the remainder of the frame  5  and laterally abuts against the main bodies  22  of the supporting pins  4  of the supporting field  2 . Thus the supporting pins are clamped between the pressure plate  17  the remainder of the frame  5 . 
     The arrangement of the fixing device  15  and the supporting pins  4  which form the supporting field  2  with their end faces  3  also emanates from the plan view according the  FIG. 2 . Here it is shown that the supporting pins  4  in the present embodiment of the apparatus are arranged in a square pattern. A hexagonal pattern is also possible. 
     For the purpose of function monitoring, the apparatus  1  comprises a detection device  23  having a light barrier  18 . The light barrier  18  includes a light source  19  and a light sensor  20 , which face one another across the main extension directions  6  of the supporting pins  4 . In the main extension directions  6 , the light source  18  is positioned such that, with completely reset supporting pins  2  as they are depicted in  FIG. 1 , their retainer rods  8  do not extend into the light path  21  between the light source  19  and the light sensor  20  of the light barrier  18 . In this way, the light barrier  18  monitors whether the supporting pins  4  are not yet pressed-in or have already been completely reset. If only one of the supporting pins  4  with its retainer rod  18  extends into the light path  21 , the light intensity registered by the light sensor  20  is reduced with respect to a maximum light intensity with free light path  21 . If such a reduction of the light intensity occurs, although the supporting pins  4  should be reset, this indicates a failure of the apparatus  1 . This failure is acknowledged by a controller  24  of the detection device  23 , and results in that the controller  24  outputs a failure signal  25 . The controller  24  also detects whether the fixing device  15  and the pressurized air source  14  are active, or it purposeful deactivates them which, however, requires a design of the fixing device  15  including an actuator. 
       FIG. 3  illustrates a division of the light source  19  of the light barrier  18  into six sub-sources  19   a  to  19   f  and of the light sensor  20  into six sub-sensors  20   a  to  20   f,  wherein each one sub-sensor  20   a  to  20   f  faces one of the sub-sources  19   a  to  19   f  across a row of supporting pins  14 . By sequentially activating the sub-sources  19   a  to  19   f  and separately registering light intensities with the sub-sensors  20   a  to  20   f,  a supporting pin  4  getting into the light path  21  of the light barrier  18  with its retainer rod  8  can be localized or a number of supporting pins  4  getting into the light path  21  may be estimated and localized. 
     With the light barrier  18  which is outlined in  FIG. 4  and in which the light source  19  is divided into a total 12 sub-sources  19   a  to  19   l  and the light sensor  20  is divided into a total of 12 sub-sensors  20   a - 20   l,  wherein one sub-source  19   a  to  19   l  and one sub-sensor  20   a  to  20   l  face each other across each row and each column of the supporting pins  4  of the supporting field  2 , it is even better possible to make this estimation. 
     On the other hand,  FIG. 5  outlines how dividing the light source  19  into three sub-sub-sources  19 A to  19 C and the light sensor  20  into three sub-sub-sensors  20 A to  20 C in the main extension directions  6  of the supporting pins  4  allows for better detecting how deep the supporting pins  4  are pressed-in, because, depending thereon, they enter into different sub-paths  21 A to  21 C of the light path  21  of the light barrier  18 . 
     Many variations and modifications may be made to the preferred embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the present invention, as defined by the following claims.