Abstract:
An apparatus for detecting the presence of a workpiece carrier in a predetermined track portion of a workpiece carrier transporting path has a housing, a slider which is displaceably guided in the housing and is displaced by the workpiece carrier, at least one proximity switch which is releasable by the slider, two turning elements provided with teeth and arranged on the housing, each of the turning elements being supported turnably around an axis provided on the housing, the turning elements being in tooth engagement with one another, the turning elements being also in tooth engagement with linear tooth sets provided on opposite sides of the slider and extending in a linear displacement direction.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an apparatus for detecting the availability of a workpiece carrier in a predetermined track portion of a workpiece carrier transportation path, which includes a housing, a slider which is displaceably guided in the housing and displaced directly or indirectly by the workpiece carrier, and at least one proximity switch releasable by the slider.  
         [0002]     Such apparatuses are known in the prior art and identified as “rockers”. They can be arranged for example laterally on the workpiece carrier transporting path for detecting the transitional movement of a workpiece carrier ( FIG. 1 ). The workpiece carrier is brought in engagement with the slider of the rocker and deviates it in a direction which is substantially orthogonal to the movement direction of the workpiece carrier. The displacement movement of the slider can be detected by a proximity switch. The output signal of the proximity switch can be used to control further steps, for example a processing step to be started on a workpiece arranged on the workpiece carrier.  
         [0003]     It is however also possible to allow running of the workpiece carrier head-on against the rocker so that the slider is displaced by the workpiece carrier substantially in its movement direction ( FIG. 2 ). In this case the output signal of the proximity switch can set in operation for example a pushing device or a transferring device which transfers the workpiece carrier from the current transporting path to the next following transporting path.  
         [0004]     Conventionally, the slider in the known rockers is displaceably guided in the housing by means of cooperating wall surfaces of the slider and the housing.  
         [0005]     The disadvantage of the known constructions of such rockers include first of all the fact that during engagement of the workpiece carrier and the slider a tilting of the slider, and if worse come to worse, a turning and clamping of the slider in the housing can occur. The switching conditions of the proximity switch released by the slider can not be reproduced in this case with the required accuracy, in particular a switching delay can occur.  
       SUMMARY OF THE INVENTION  
       [0006]     Accordingly, it is an object of the present invention to provide an apparatus for zone monitoring, which avoids the disadvantages of the prior art.  
         [0007]     More particularly, it is an object of the present invention to provide an apparatus for zone monitoring, in which switching conditions can be reproducible with a desired precision.  
         [0008]     In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated in an apparatus for zone monitoring, in which in the housing two turning elements are provided which have teeth and are formed so that each of the turning elements is turnable about an axis which is supported or arranged on the housing, and the both turning elements on the one hand are in engagement by their teeth with one another and on the other hand are in tooth engagement with linear teeth provided on opposite sides of the slider and extending substantially in a linear displacement direction.  
         [0009]     By the cooperation of the linear teeth arranged on the slider and the turning elements supported on the housing, it is guaranteed that the linear teeth and thereby the opposite sides of the slider, on which the linear teeth are provided, are displaced with the same speed in the housing. Thereby a tilting or turning of the slider in the housing can no longer occur. The same is true with respect to a displacement of the slider out of the housing, which is caused for example by a restoring spring.  
         [0010]     It should be mentioned that the use of toothed elements as such is known, but not in the technical field relating to the present invention. For example German patent document DE 44 30 046 C2 discloses a safety load switching device with a plurality of safety units, in which for performing the switching movement each of the safety inserts is provided with a toothed wheel-toothed rack drive. This transverses a turning movement of a hand operating lever into a linear movement of the safety inserts. Japanese patent document JP-2001-1265828 discloses a key for a keyboard, on which the axis of two turnable and toothed-engageable sector discs are supported. The free ends of two elongated projections of these sector discs are guided linearly displaceably on a base plate of the keyboard.  
         [0011]     In the inventive apparatus a space-saving arrangement of the toothed elements engaged with one another is obtained, in that at least one turning element is formed as a turning lever which is provided on its both free ends correspondingly with a set of teeth.  
         [0012]     The linear teeth can be formed basically on specifically designed toothed rods which are mounted on the slider. Preferably the linear teeth can be worked in a wall of the slider which extends in the housing. In both cases the linear teeth run for example substantially in the linear displacement direction of the slider.  
         [0013]     In accordance with a further embodiment of the invention, it is proposed that the proximity switch is an inductive proximity switch or a pneumatic proximity switch. The housing in this case can be provided both with a receptacle for an inductive proximity switch and with a receptacle for a pneumatic proximity switch. When the inductive proximity switch is provided, the slider can be provided with a preferably metallic actuating element, for example a metal plate for releasing the proximity switch.  
         [0014]     For facilitating the linear displacement of the slider by the workpiece carrier, in particular in the case of the lateral arrangement of the inventive apparatus on the workpiece carrier transporting path, in accordance with a further embodiment of the invention it is proposed that a slider or an element mounted on the slider has at least one facial running incline, which can be inclined relative to the linear displacement direction, for example by an angle of between 45° and 90°, preferably substantially 65°. For the case of the frontal action of the workpiece on the slider, the slider or the element mounted on it moreover can be provided with an abutment surface which is arranged substantially orthogonal to the linear displacement direction.  
         [0015]     As mentioned above, a restoring spring can be further provided, which pre-stresses the slider to an actuation-ready position, or in other words to a position in which it is ready to perform a linear displacement movement under the action of a workpiece carrier, with which the at least one proximity switch is released.  
         [0016]     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. the invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIGS. 1 and 2  are schematical plan views of two workpiece carrier transporting paths provided with an inventive apparatus;  
         [0018]      FIG. 3  is a perspective view of the apparatus in accordance with the present invention; and  
         [0019]      FIG. 4  is a partially sectioned plan view in direction of arrow IV in  FIG. 3  for illustration of the guidance of the slider in the housing.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     An apparatus for zone monitoring in accordance with the present invention is identified in general with reference numeral  10 . It is arranged laterally on a workpiece transporting path  12  which transports a workpiece carrier  14  in direction of the arrow F. The apparatus  10  serves for detecting the transitional movement of the workpiece carrier  14  and transmitting a corresponding detection signal through a signal conductor  16  to a not shown control unit, which in turn controls a not shown apparatus for treatment of a workpiece  18  arranged on the workpiece carrier  14 . In the case shown in  FIG. 1 , the workpiece carrier  14  deviates a slider  22  which is displaceably received in a housing  20  of the apparatus, into a stroke direction H which extends substantially orthogonally to the transporting direction.  
         [0021]     As can be seen from  FIG. 2 , it is however basically also possible to run the workpiece carrier  14  which is transported by the transporting path  12 , in direction of the arrow F head-on against an inventive arrangement  10 ′. In other words the stroke direction H of the slider  22 ′ in the housing  20  extends substantially parallel to the transporting direction F. The signal provided from the apparatus  10 ′ can be used in this case for example for controlling a transfer device  24 , which transfers the workpiece carrier  14  from the transporting path  12  to a subsequently arranged transporting path  26 , which then transports the workpiece carrier  14  in direction F′.  
         [0022]     Such apparatuses  10  and  10 ′ are known by experts as rockers.  
         [0023]      FIG. 3  shows the inventive apparatus or rocker  10  in perspective. It includes, as explained herein above, the housing  20  and the slider  22  which is displaceably received in the housing  20 . In the shown embodiment a projection  28  is further provided on the slider  22 . This projection  28  can serve on the one hand as a wear-protection element for the slider  22 . It can also be used, with a corresponding dimensioning of its thickness, as a spacer adapting piece between the arrangement point of the rocker  10  on the transporting path  12  and the workpiece carrier  14 .  
         [0024]     Inclined surfaces  22   a  and  28   a  are formed on the slider  22  and on the projection  28 . They serve as running inclines for the workpiece carrier  14  and thereby facilitate a displacement movement of the slider  22  into the housing  20 . These inclined surfaces include an angle α with the transporting direction F of the workpiece carrier transporting path  12 . The angle α can be within the range from 0° to substantially 45° and preferably is equal to substantially 25° as shown in  FIG. 1 . The angle 90°-α enclosed between the inclined surfaces  22   a  and  28   a  and the linear displacement direction H correspondingly has a value of between substantially 45° and substantially 90° and preferably substantially 65°. An abutment surface  22   b  or  28   b  is provided between both inclined surfaces  22   a  and  28   e  on the slider  22  and on the projection  28 . The workpiece carrier  14  runs against these abutment surfaces in the arrangement shown in  FIG. 2 .  
         [0025]      FIG. 4  shows a mechanical system, which guarantees that the slider  22  during displacement into the housing  20 , as well as during displacement out of the housing  20 , is not tilted in the housing  20 , but instead also with a lateral abutment of the workpiece carrier  14 , or in other words in the arrangement shown in  FIG. 1 , moves in the housing  20  in a tilting-free manner.  
         [0026]     A basic guidance of the slider  22  on the housing  20  is performed by two pins  30  which are arranged or supported on the housing  20  and extend through longitudinal holes  32  formed in two walls  34  arranged opposite to one another and extending in the housing  20 . Only one of the walls, out of the two walls  34  of the slider  22 , is shown in  FIG. 4  due to the cross-sectional view. The pins  30  slide along outer limiting edges  32   a  of the longitudinal holes  32 .  
         [0027]     Two walls  36  which connect the walls  34  on the slider  22  with one another and extend substantially orthogonal to the walls  34 , are arranged at a distance from the side walls  20   a  of the housing  20 .  
         [0028]     The above mentioned pins  30  serve as bearing axles or bearing shafts for two turning levers  38  and  40 , which are provided on their free ends with sets of teeth  38   a ,  38   b ,  40   a ,  40   b . Moreover, linear sets of teeth  42  and  44  are provided on the inner side of the walls  36  of the slider  22 . These linear tooth sets can be formed for example on tooth rods, which are mounted on the inner side of the wall  36  or are formed directly on or in the inner side of the walls  36 .  
         [0029]     As shown in  FIG. 4 , the linear tooth set  42  is in tooth engagement with the tooth set  38   b  of the turning lever  38 . Furthermore, the tooth set  38   a  of the turning lever  38  is in tooth engagement with the tooth set  40   b  of the turning lever  40 . The tooth set  40   a  of the turning lever  40  is finally in tooth engagement with the linear tooth set  44 .  
         [0030]     When a workpiece carrier  14  shown in  FIG. 4  in a broken line runs in the transporting direction F against the left side of the slider  22  or the projection  28  in  FIG. 4 , or more accurately against its inclined surface  28   a , then the left side of the slider  22  is displaced into the housing  20 . Due to the different tooth set engagements  42 / 38   b ,  38   a / 40   b  and  40   a / 44  this insertion movement of the left side of the slider  22  is transmitted also to its right side, so that both sides of the slider  22  move with the same speed into the housing  20 . In this case a tilting of the slider  22  in the housing  20  can be avoided, which in conventional rockers based on the one-side engagement workpiece of the carrier  14  leads to a the risk of a switching delay.  
         [0031]     It should be added that between the rear wall  20   b  of the housing  20  and the slider  22 , a restoring spring  46  is arranged. It moves the slider  22  after the transition movement of the workpiece carrier  14  again out of the housing  20 . This movement is limited by abutment of the pins  30  against end sides of the longitudinal holes  32  which are covered in  FIG. 4  by the turning levers  38  and  40 .  
         [0032]     It should be further mentioned with respect to  FIG. 3  that in the housing  20  of the inventive rocker  10 , receptacles  50  and  52  are provided for two proximity switches. For example, in the receptacle  50  an inductive proximity switch  58  can be arranged, and the receptacle  52  a pneumatic proximity switch  60  can be arranged. The connecting points  54  for one of these proximity switches are schematically shown in  FIG. 3 . As for the provision of the inductive proximity switch  58 , a metal plate  56  is moreover arranged on the slider  20  as shown in  FIG. 4 .  
         [0033]     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.  
         [0034]     While the invention has been illustrated and described as embodied in, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.  
         [0035]     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of the invention.