Abstract:
The invention relates to a measuring device, which allows the thickness of an elongated, panel-type workpiece, lying on a reference plane and traveling along the reference plane, to be continuously recorded. The measuring device is provided with a guide shoe, which is bath-shaped and open at the top and is pivotally mounted in a machine frame on parallelogram-shaped steering elements. A measuring roller, which projects slightly out of a cavity in a base section that runs parallel to the reference plane, is located inside the guide shoe. The measuring roller is supported in the interior of the guide shoe by rollers on both sides of the recess. The measuring roller is in contact with the reference plane and after a deflection of the guide shoe, comes into contact with the measuring surface of the workpiece, a measured value that represents the thickness being derived from the deflection.

Description:
FIELD OF THE INVENTION 
   The invention relates to a measuring device for continuously measuring and recording the thickness of elongate panel type objects. 
   BACKGROUND OF THE INVENTION 
   In order to check the thickness of elongate measurement objects, e.g. long timbers or panel-shaped material to be measured, it is known to provide a measuring system which is characterized by at least one measuring roller which is held above the measurement object and can be moved in the direction towards same. The zero setting of the measuring roller which is operatively connected to a pneumatic drive is formed by means of a reference plane, on which lies the measurement object and along which said measurement object can be moved at a defined speed. For its part, the measuring roller is also operatively connected to a measuring transducer, by means of which the displacement path of said measuring roller can be represented by a corresponding electrical signal. 
   The measuring procedure in the case of this known measuring system is performed in such a manner that the measuring roller is moved out from its withdrawn position above the measurement object in the direction of said object and brought into contact therewith, after the moving measurement object has arrived at a position below the measuring roller. However, in dependence upon the advance speeds of the measurement object on the one hand and the measuring roller on the other hand, it is not possible as a result to record the thickness of a starting region of the measurement object. Furthermore, the measuring roller is withdrawn starting from its position rolling on the surface of the measurement object, before the end of the measurement object is reached. This limitation at the beginning and the end of the measuring path on the measurement object was adapted inter alia to avoid causing any mechanical damage to the measuring system. 
   In order to improve the manner in which the measuring systems are protected from mechanical destruction measuring devices are currently used, in which a run-in ramp is provided. For this purpose, a run-in ramp is provided which is mounted on its end so as to be able to pivot about an axis in parallel with a reference plane. This run-in ramp is operatively connected at its free end facing away from its articulation to a measuring roller which by means of running rollers on both sides is supported on the inner side of this ramp and passes slightly through the base region thereof. 
   By reason of the measurement object which abuts against the underside of the base region of the run-in ramp, said run-in ramp is pivoted, wherein during the course of further advance movement the measuring roller finally moves into position against the surface of the measurement object. In dependence upon the advance speed and also upon the comparatively long lever arm between, on the one hand, the articulation point of the run-in ramp and, on the other hand, the measuring roller, extraordinarily high acceleration moments are produced for the measuring roller and above all the elements of the measuring systems which are functionally downstream of the measuring roller. In order to avoid vibration problems which arise due to an acceleration of the run-in ramp, there is provided a control, which is allocated to the pneumatic drive of the measuring roller, with the proviso that a counter force is developed at an early stage which suppresses excessive vibration. However, the disadvantage in this case is that the acceleration moments which are to be compensated are dependent both upon the advance movement of the measurement object and also upon its thickness. 
   The purpose of this known measuring system is to obtain the most complete information possible on the thickness of the measurement objects—as seen in the longitudinal direction thereof—wherein the measurement objects are guided through the measuring system at a defined advance speed and at different mutual end-side spaced intervals. One essential feature of these known measuring systems is that each time a measurement object has been passed through by means of the said pneumatic drive, the measuring roller is moved either to a withdrawn position or to a zero setting. The periods of time available for these considerable deflection movements turn out to be comparatively short in dependence upon the advance speed of the measurement objects and the mutual spaced intervals between them and consequently these periods must be concluded at a correspondingly high speed and with rapid reverse-control procedures. In addition to high material stress, this can also lead to considerable noise development. As a result, these conditions restrict the advance speed of the measurement objects. 
   SUMMARY OF THE INVENTION 
   Against this background, it is the object of the invention to design a measuring device of the type stated in the introduction with the proviso that the mechanical stress of the actual measuring system, in particular that of the measuring roller and the function elements disposed downstream thereof is reduced and in relation to the prior art set forth in the introduction it is possible to achieve an increase in the speed at which the measurement objects are advanced. In the case of this type of measuring device, this object is achieved by using a roller that can be moved toward and away from a reference plane. The roller is associated with a transducer which generates an electric signal. A measured value that represents the thickness of the object is derived from the signal based upon the motion of the roller. A guide shoe is disposed on pivoting links in the manner of a four-bar linkage and has an opening that accommodates the roller. The shoe has a base section that extends parallel to a reference plane from which the thickness of the objects is measured. 
   Accordingly, an aspect of the invention is a guide shoe which comprises a base section which extends in parallel with the reference plane and said guide shoe is pivotally disposed with respect to the machine frame by way of parallelogram-shaped levers. The end points of the parallelogram-shaped levers which form the articulation points thereof lie on the corners of a parallelogram, so that the parallelism between the base section and the reference plane is also maintained during the pivot movement of the guide shoe. 
   Supported on the guide shoe, lying opposite the reference plane, is the measuring head, of which the measuring roller passes slightly through a recess in the said base section. The measuring roller is intended to roll on the measurement object in a manner which is known per se. 
   As such the guide shoe is intended to be deflected, in particular pivoted, by an abutting measurement object, wherein the vertical component of the pivot movement is used in order to displace the measuring head. 
   As a result of the articulation of the guide shoe in the manner of parallel steering elements and of which the parallelogram-shaped levers extend virtually perpendicularly in a starting position or in such a manner that the respective lower articulation points are slightly deflected in the direction in which the measurement object is advanced, the abutment of the measurement object against the facing base region of the guide shoe causes said guide shoe to perform a movement which is made up of “simultaneous movement” in the advance direction and a vertical movement. The movement referred to lastly is linked via a sine function to the pivoting movement of the parallelogram-shaped levers, in particular their pivot angle about their upper articulation points, so as to produce in comparison with the prior art an extraordinarily small initial vertical acceleration and therefore loading of the measuring roller or the elements functionally downstream thereof. 
   Corresponding to the conditions, set by the length of the parallelogram-shaped levers and the geometric formation of the guide shoe base region facing the measurement object, the measuring system, in relation to the prior art set forth in the introduction, is subjected to substantially lower acceleration at the same advance speed, wherein the thickness of the complete length of the measurement object is measured. In turn, these acceleration conditions allow comparatively higher advance speeds, without the problem of excessive material stress arising. 
   Running rollers, positioned preferably on each side of the opening in the guide shoe, support the measuring roller. Since the measuring system can only be moved vertically, it is necessary to provide a movable support on the guide shoe in parallel with the reference plane. 
   The links supporting the guide shoe in its non-deflected state are angularly deflected in the direction which the objects to be measured move relatively to the guide shoe. It is advantageous that the guide shoe is held under resilient force in position against the running rollers. This resilient force in conjunction with the counter force applied by way of the drive of the measuring system serves to produce the measuring force which determines the contact pressure of the measuring roller on the measurement object. 
   The base region of the guide shoe is intended to cooperate directly inter alia with the edges or the surface of the measurement object to be treated. Its geometric shape in conjunction with the parallel-articulation of the guide shoe on the machine frame serves to influence significantly the movement and in particular the acceleration conditions of the measuring system. The guide shoe consists of a series arrangement of a comparatively steep ramp section, a comparatively flat ramp section, the base section, a comparatively flat ramp section and a comparatively steep ramp section. Two of the ramp sections are inclined in a descending manner and two are inclined in an ascending manner in the direction of travel of the objects to be measured. 
   Basically, the movements of the measuring system should be kept as small as possible and this is demonstrated initially by virtue of the fact that the measuring system is held between two consecutive measurement objects by means of its drive, e.g. a pneumatic drive, in a particular displacement position corresponding to the measured value of thickness of the respectively preceding measurement object. Equally, there is no complete withdrawal movement or a movement to a zero setting. The control device is set up in conjunction with peripheral elements associated therewith such that the drive of the measuring system in this sense is then controlled if the gap between two measurement objects is greater than a distance determined by the longitudinal extension of the guide shoe. If, conversely, the gap between two measurement objects is shorter than this distance, a corresponding reverse-control of the drive of the measuring system is omitted. This basic actual value storage of a measured value of thickness of a preceding measurement object produces a substantially lower level of mechanical stress on the measuring system, lower noise development and a lower energy requirement for the drive of the measuring system, i.e. lower air consumption in the case of a pneumatic drive. 
   It is also possible to reset the measuring head in a very short time by reason of the short displacement path. 
   Other embodiments of the measuring device in accordance with the invention, include a second guide shoe disposed and articulated below the object to be measured. The second guide shoe is connected to a second measuring system including a second measuring roller intended to scan the underside of the object, and wherein a measured value of thickness of the measurement object is derived from the displacement of the two measuring rollers with respect to a reference plane, so that in general the difference in the displacement of the two measuring rollers is measured. Preferably, it will be assumed that in comparison with the upper measuring roller, the lower measuring roller is only displaced slightly with respect to the reference plane, so that the lower measuring roller is operated without a guide shoe. However, it is also possible to operate the lower measuring roller with a guide shoe which structurally can correspond to the upper guide shoe, wherein by means of a corresponding actuation of the drive allocated to the lower guide shoe or to the lower measuring system, it is necessary to ensure that the guide shoe or the measuring roller lies in position against the underside of the measurement object. 
   In order to increase the operational security of the measuring device, in particular for protecting the measuring system in the event of a malfunction in the energy supply to the drive, the control device is arranged in such a manner that in the event of an interruption in the power supply to the drive, the measuring system remains in its last position or is moved to a withdrawn position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a side view of a measuring device to be ascribed to the prior art in a partial sectional illustration; 
       FIG. 2  shows a side view of the measuring device according to the invention in a partial sectional illustration; 
       FIG. 3  shows a side view of the guide shoe used within the framework of the measuring device according to a sectional plane III—III in  FIG. 3 ; 
       FIG. 4  shows a plan view of the said guide shoe according to the arrow IV in  FIG. 3 ; and 
       FIG. 5  shows a side view of an alternate embodiment of the measuring device according to the invention. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   In  FIG. 1 , the reference numeral  1  designates a panel-type measurement object which lies on a reference plane  2  and is moved at a defined speed in the direction of the arrow  3 . The measurement object  1  comprises a finite thickness  4  perpendicular to the said reference plane  2 , of which the progression—as seen in the longitudinal direction of the measurement object  1 —is to be recorded during the passage of the said measurement object through the measuring device  5 . The longitudinal extension of the measurement object  1  in this case runs parallel with the reference plane  2 . 
   The reference numeral  6  designates a run-in ramp which is formed as an elongate bath-shaped basic body which is open on the upperside and which is articulated at its one end in a bearing block  8 , which is affixed to a machine frame  7 , so as to be able to pivot about a horizontal axis extending perpendicularly to the advance direction  3 . The bearing block  8  is located at a spaced interval above the reference plane  2 . 
   The reference numeral  9  designates a measuring roller which in the illustration shown lies on the reference plane  2  and in this case passes through a recess [not illustrated in the drawing] of the base region  10  of the run-in ramp  6 . The measuring roller  9  is mounted at the end of a measuring linkage  11  in such a manner as to be able to rotate about an axis extending in parallel with the reference plane  2  and perpendicularly to the advance direction  3 , wherein the entire system consisting of the measuring roller  9  and the measuring linkage  11  forms a measuring system which is operatively connected to a measuring transducer which is also not illustrated in the drawing. Its functional principle is to convert vertical movements of the measuring roller  9  with respect to the reference plane  2 , i.e. in the direction of the arrows  12 , into an electrical signal. This signal is transmitted to a control device and further processed in a suitable manner, in particular it is illustrated visually, stored etc.. 
   The said measuring system is vertically supported on the inner side of the base region  10  by means of freely rolling running rollers  13  which are mounted on the measuring linkage  11  with the proviso that the measuring roller  9  protrudes by a defined distance from the underside of the run-in ramp  6 . 
   Also not illustrated in the drawing is a drive, e.g. a pneumatic drive which is connected to the said control device and by means of which the measuring system can be displaced in the direction of the arrows  12 . 
   The principle of this known measuring device is that by reason of the measurement object  1  which is moved at a defined speed in the advance direction  3  and which abuts with its edge  14  against the base region  10  of the run-in ramp  6 , the said run-in ramp is pivoted about the axis of the bearing block  8 , wherein this pivot movement triggers a vertical movement of the measuring linkage  11  by way of the said running rollers  13 . This pivot movement ultimately causes the measuring roller  9  to roll on the upper side  15  of the measurement object, wherein according to the vertical deflection of the measuring system via the measuring transducer a corresponding measured value is generated. In each case, the aim is to record the progression of the thickness  4  of the measurement object in the direction of its longitudinal extension. 
   However, in dependence upon the thickness  4  of the measurement object  1  and the spaced intervals between the articulation point  8 ′ of the run-in ramp  6  on the one hand and the primary abutment point of the measuring point  1  against the said base region  10  or the running rollers  13  on the other hand, considerable vertical acceleration of the measuring system is achieved. In particular, the relationship of the spacing of the running rollers from the articulation point to the spacing of the said abutment point from the articulation point serves accordingly to enhance the deflection movement of the run-in ramp  6  at the point where it interacts with the running rollers  13  and therefore the measuring system. 
   In order to avoid vibration problem and also to protect the measuring system mechanically, these kinematic boundary conditions render it necessary to develop a counter force by way of the drive allocated to said system, in coordination with the deflection movement of the run-in ramp  6 . On the whole, these characteristics particularly in the case of measurement objects having comparatively large thickness dimensions inevitably serve, however, to limit the advance speed of the measurement object  1  considerably. 
   In the embodiment of a measuring device according to the invention illustrated by way of example in  FIGS. 2  to  4  and explained in detail hereinunder, functional elements which correspond to those in  FIG. 1  are numbered accordingly. 
   The reference numeral  16  designates a guide shoe which is mounted in a manner to be explained in detail hereinunder so as to be able to swing on the machine frame  7  and comprises a base section which is intended and arranged to cooperate with the measurement object  1 . Seen from left to right, the base section consists of the series arrangement of a first comparatively steep ramp section  17 , which extends e.g. at an angle of 45° with respect to the reference plane  2 , a ramp section  18  adjoining said first ramp section and extending at a substantially shallower angle with respect to the reference plane  2 , an adjoining base section  19  extending in parallel with the reference plane, a ramp section  20  which adjoins the last named base section and ascends with respect to the reference plane  2  in turn at a comparatively shallow angle, and an adjoining ramp section  21  extending at a comparatively steeper angle with respect to the reference plane  2 . Adjoining the said ramp sections  17  to  20  is a sidewall  21 ′, so that the guide shoe  16  generally has a bath-shaped configuration which is open towards the upper side. 
   The reference numeral  22  designates two identically configured parallelogram-shaped levers which are in particular the same length and which are articulated in a pivotal manner on the horizontally mutually spaced points  23 ,  24  of the machine frame  7 . The points  23 ,  24  can each be formed by bolts which are located in a common horizontal plane. 
   Perpendicular to the plane of the drawing in  FIG. 2 , the parallelogram-shaped levers  22  are disposed in each case in pairs at a spaced interval with respect to each other, wherein their respective lower ends, i.e. the end remote from the points  23 ,  24 , are articulated in a pivotal manner in points  25 ,  26  of the sidewalls  21 ′ of the guide shoe  16 , which points  25 ,  26  are located in turn in a common horizontal plane. In the starting position of the guide shoe  16  shown in  FIG. 1 , the two parallelogram-shaped levers  22  extend at an acute angle with respect to vertical planes extending through the points  23 ,  24 , and furthermore such that the lower points  25 ,  26  are offset in the direction of the arrow  3  with respect to the upper points  23 ,  24 . It is evident in these embodiments that the arrangement of the parallelogram-shaped levers forms a parallel steering arrangement for the guide shoe  16 . It is essential that, with respect to the plane of the drawing in  FIG. 1 , on the one hand the-points  23 ,  24  and on the other hand the points  25 ,  26  lie in each case on mutually parallel straight lines which also extend in parallel with the base section  19 . 
   The reference numeral  27  designates a draw spring, of which one end is articulated on a point  28  located at a small spacing from the point  23  on the end of the parallelogram-shaped lever  22  facing said point, and the other end of said draw spring is articulated to a point  29  on the sidewall  21 ′ of the guide shoe  16  which is spaced apart from the point  25  at this site. Each of the two parallelogram-shaped levers  22  which are adjacent to each other perpendicular to the plane of the drawing in  FIG. 1  are allocated such a draw spring  27 . It is evident that under the influence of the draw springs  27 , the guide shoe  16  is drawn under spring bias towards the measuring system to be described hereinunder. 
   The reference numeral  9  designates a measuring roller which in the illustration shown in  FIG. 2  lies on the reference plane  2  and in this case passes through a recess  30  in the base section  19  of the guide shoe  16 . The measuring roller  9  is mounted on a roller holder  31  in such a manner as to be able to rotate about an axis  32  extending in parallel with the reference plane  2 . The roller holder  31  is connected to a vertically mounted measuring linkage  33  which is operatively connected to a measuring transducer  40 . The principle of said measuring transducer is based upon the fact that vertical movements of the measuring roller  9  with respect to the reference plane  2 , i.e. in the direction of the arrows  12 , are converted into an electrical signal, preferably a digital signal. This signal is transmitted to a control device and visually displayed, stored etc. therein in a suitable manner. 
   As illustrated in  FIG. 4 , the measuring roller  9  is located according to the positioning of the recess  30  in a central region of the base section  19 , wherein on both sides of the roller holder  31 , running rollers  34  are each mounted in such a manner as to be able to rotate about axes  35  in parallel with the axis  32  but below same. Both axes  32 ,  35  extend horizontally and perpendicularly with respect to the arrow  3 , wherein the two running rollers  34  are disposed laterally in relation to the measuring roller  9  and therefore in the regions  36  on both sides of the recess  30  are mounted in such a manner as to be able to roll on the base section  19  of the guide shoe  16 . The axes  32 ,  35  are positioned in conjunction with the diameters of the measuring roller  9  on the one hand and the running rollers  34  on the other hand with the proviso that—as shown in  FIG. 2  of the drawing—the measuring roller  29  protrudes slightly out of the underside of the guide shoe  16 . 
   The measuring linkage  33  is also operatively connected to a drive  41 , schematically shown in  FIG. 2 , e.g. a pneumatically actuated piston-cylinder unit by means of which the running rollers  34  are held in position against the guide shoe  16  in the regions  36  and in conjunction with the draw springs  27  the required measuring force is applied. A reverse control  42  for controlling motion of the transducer including its associated measuring roller  9  is operatively associated with drive  41 . The reverse control operates to hold the measuring roller  9  at a height position corresponding substantially to a thickness of a first of the objects  4  when the distance between the first object and a second object on the reference plane  2  exceeds a distance determined by the longitudinal extension of the guide shoe  16 . The statements above show that the functional principle of the measuring device in accordance with the invention is based upon the fact that the guide shoe  16  can be pivoted by reason of its articulation on the points  23 ,  24 , wherein only the vertical component of the total movement of the guide shoe  16  is transmitted by way of the running rollers  34  to the measuring linkage  33 . The measurement object  1  which is moved in the direction of the arrow  3  in parallel with the reference plane  2  abuts with its corner  37  against the steeply extending ramp section  17  of the guide shoe  16 , with which the deflection procedure of the guide shoe  16  about the points  23 ,  24  commences. The continuation of the deflection movement of the guide shoe  16  is determined kinematically by the consecutive ramp sections  17 ,  18 , in particular their absolute lengths and angles with respect to the reference plane  2 . Since merely the vertical component of the pivot movement of the guide shoe  16  is transmitted by way of the measuring roller  9 , in comparison with the prior art set forth in the introduction a substantially lower vertical acceleration is achieved for the measuring roller  9  including functional elements disposed downstream thereof in the direction of the arrows  12 . According to the angles of the consecutive ramp sections  17 ,  18  and of the base section  19 , the pivot movement of the guide shoe  16  is characterised by an initially rapid acceleration which in the region of the ramp section  18  is characterised by a very much lower acceleration, in particular in the vertical direction also. 
   Starting from a “zero-setting” of the measuring system, in which the measuring roller  9  records the level of the reference plane  2 , the measurement object  1  moving in the direction of the arrow  3  causes the guide shoe  16  and thus the measuring roller  9  to deflect to the actual value of the thickness  4  of the measurement object  1 , wherein as a consequence the progression of this thickness value in the longitudinal direction of the measurement object  1  is scanned and logged. During this measuring procedure—as seen in the longitudinal direction of the measurement object  1 —the measuring roller  9  is in contact with the side of the measurement object  1  facing it. Upon reaching the end of the measurement object  1 , this state of deflection of the measuring roller  9  is stored as the desired value for the value of the thickness  4  of the subsequent measurement object. By way of the drive allocated to the measuring linkage, the running rollers  34  are held constantly in position against the base section  19 . 
   In the event that the spacing between two consecutive measurement objects  1 —as seen in the direction of the arrow  3 —is smaller than a distance determined by the longitudinal extension of the guide shoe  16 , so that by reason of the fact that the guide shoe  16  lies against the consecutive measurement objects  1 , the guide shoe  16  is not able to pivot in any event up to the level of the reference plane  2 , this spacing can be bridged without reversing the control of the drive of the measuring linkage  33 . 
   In contrast, if the said gap turns out to be larger than the distance determined by the longitudinal extension of the guide shoe  16 , reversing the control of the drive of the measuring linkage  33  ensures that said linkage remains in the last extended position and in any event is not moved down to the level of the reference plane  2 . In actual fact, the measured value of the thickness of a measurement object  1  is stored as a desired value for the next measurement object  1 . For this mode of operation it is necessary that the speed and the position of the measurement objects  1  can be established precisely by suitable sensors and that signals describing the status of movement and the position of the measurement objects are available in the higher-ranking control which serves also to control the drive of the measuring head. In each case, any recording of a measured value between two measurement objects is suppressed. 
   By reason of the measuring linkage movement which is caused by the configuration of the guide shoe  16  and is performed at a lower acceleration in comparison with the prior art, and also by reason of the opportunity provided by the guide shoes of bridging two consecutive measurement objects or storing the actual value of the thickness of the respectively preceding measurement object, there is also the advantage of substantially lower noise development in addition to a lower wear-inducing operation of the measuring device, reduced energy requirement or consumption of compressed air. 
   A measuring device in accordance with the invention has been described in the above presentation such that on one side of a reference plane  2  there is located a measuring system which cooperates with a guide shoe  16 . For example, as shown in FIG.  5 . this functional principle can be extended in an alternate embodiment such that below the measurement object  4  to be measured, there is located a substantially similar measuring device including a measuring roller  9 ′ which in the same manner as the measuring roller  9  located above the measurement object  4  forms a part of a measuring system. Measuring the thickness in this case is based upon an evaluation of the deflection of the two measuring rollers  9  and  9 ′, hence upon the formation of a difference value. 
   The alternate embodiment of  FIG. 5  includes a second elongated guide shoe  16 ′ being positionable to engage a surface of the object  4  opposite that of the first shoe  16 . The second guide shoe  16 ′ has a bottom surface  18 ′ engageable with the object  4  as it moves past the device between the first and said second shoes  16  and  16 ′. The bottom surface of the second shoe has an opening therein to permit the second roller  9 ′ to extend through the second guide shoe  16 ′ for engagement with object  4 . As further shown in FIG.  5 . the measuring device positioned below the object  4  is substantially the same in configuration and operation as the device described above. Corresponding components are marked with a primed reference character, and due to the substantially similar nature of both devices a further detailed description of the alternate embodiment is superfluous.