Abstract:
A counting device associated with a conveying device for conveying flexible flat objects, such as printed products, in an overlapping stream. The counting device includes a slide mounted for forward and return movement along a guide which extends in the conveying direction, and a drive is provided for moving the slide along the guide at a higher speed than the conveying speed. The slide mounts a flexible contact element which engages the objects, and a sensor element which is engaged by the contact element when the contact element is deflected by engagement with a rear edge of each object, as the slide is forwardly advanced. A catch element, which is also mounted to the slide, then comes into contact with the rear edge of the object to displace the object in the conveying direction.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for counting flexible flat objects arranged in an overlapping formation, in particular printed products. 
     An apparatus of this type is disclosed by EP-A-0 408 490. A conveying device which is driven at conveying speed in the conveying direction and constructed as a belt conveyor is intended to convey objects in an overlapping formation, in which each object rests on the preceding one, in a system cycle rate. Arranged underneath the conveying device is a counting device, having a guide means which extends in the conveying direction and on which a slide is freely displaceably mounted. The slide can be moved to and fro, in and counter to the conveying direction, coordinated with the system cycle rate by means of a drive, the speed in the conveying direction, at least in one section of the guide means, being higher than the conveying speed, in order to bring a contact element arranged on the slide into contact with the rear edge of the object respectively moved past the counting device. The relative movement between the object and the slide causes the contact element to move out of the conveying area and, as a result, to activate a sensor element in order to emit a signal to a counter. In order to avoid the contact element exerting any influence on the position of the relevant object in any case, a pressure element is provided which presses the objects against the conveyor belt so that they are carried along firmly. In order to permit the counting of objects which are conveyed at irregular time intervals, coarse detection of the objects is performed and, accordingly, the contact element is activated at irregular time intervals. 
     It is an object of the present invention to provide a generic apparatus which, with a simple construction, ensures precise counting even of objects which occur at irregular intervals. 
     SUMMARY OF THE INVENTION 
     The above and other objects and advantages of the present invention are achieved by the provision of a conveying device which is driven at a conveying speed in a conveying direction and which is intended to convey the objects. A counting device includes a contact element and a sensor element mounted for movement along a guide which extends in the conveying direction, and a drive is provided for moving the elements along the guide at a higher speed than the conveying speed so as to bring the contact element into engagement with a rear region of each object conveyed past the counting device. The contact element then is deflected into engagement with the sensor element which emits a signal to a counter. 
     The object in each case interacting with a contact element is displaced in the conveying direction by means of a catch element driven together with the contact element. As a result, each object, even if the objects occur in an irregular overlapping formation, can interact only once with the contact element, which leads to extremely precise counting in a very simple way. The movement of the contact and catch element therefore does not need to be coordinated with a system cycle rate, the only condition is that the frequency with which these elements are moved cyclically in the conveying direction is at least as high as the maximum frequency with which the objects can occur. Even counting printed products with a prefold does not present any problems. The information about the time and the location at the end of the displacement by means of the catch element also means that the precise position of the object on the conveying device is known, which may be important for further processing. The apparatus is most suitable to process overlapping formations, in which the objects in each case rest on the preceding or in each case on the following object. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in more detail using exemplary embodiments illustrated in the drawing, in which, in purely schematic form: 
     FIG. 1 shows a side view of a first embodiment of the apparatus at a time at which a slide belonging to the counting device is located with a contact and a catch element in an initial, upstream position; 
     FIG. 2 shows, in an identical illustration to FIG. 1, the apparatus shown there with the slide in a final, downstream position; 
     FIG. 3 shows, in a side view and enlarged with respect to FIG. 1, part of the apparatus shown there; 
     FIG. 4 shows, in an identical illustration to FIG. 3, the apparatus with a catch element of different design; 
     FIG. 5 shows a side view of a second embodiment of the apparatus according to the invention with the slide in the initial, upstream position; 
     FIG. 6 shows, in an identical illustration to FIG. 5, the apparatus shown there with the slide in the final, downstream position; and 
     FIG. 7 shows, on an enlarged scale with respect to FIG. 6, a part of the apparatus shown there. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The apparatus shown in FIGS. 1 to  3  has a conveying device  10  designed as a belt conveyor, which is driven at the conveying speed v 1  in the conveying direction F. It is intended to convey flexible flat objects  12 , for example thin printed products, in an overlapping formation S, in which each object  12  rests on the one respectively following it. The rear edge  14 , located in the rear end region  14 ′ of the object  12 , is therefor exposed in the upward direction. In the overlapping formation S shown, the objects  12  are arranged in such a way that the distance the rear edges  14  of successive objects corresponds to a permissible minimum distance A. The distance between the rear edges  14  is, however, usually greater than this minimum distance A and, in particular, it can vary greatly in the case of an irregular overlapping formation. 
     Arranged above the conveying device  10  is a counting device  16 . It has a guide rail  18 ′ which extends n the conveying direction F and forms a guide means  18 . A slide  20  is freely moveably mounted on said guide rail. It is connected via a rod  22  to a drive  24 ′ constructed as a cylinder/piston unit  24 . The drive  24 ′ is intended to move the slide  20  from an initial, upstream position  26 , indicated by continuous lines in FIG.  1  and by dashed lines in FIG. 2, in the conveying direction F into a final, downstream position  28 , indicated with continuous lines in FIG. 2, and back again in a cyclic manner. The stroke H of this movement is smaller than the permissible minimum distance A between the rear edges  14  of successive articles  12 . The speed v at which the slide  20  is moved in the conveying direction F is, at least in one section of the guide means  18 , higher than the conveying speed v 1 . In the present case, the cylinder/piston unit  24  is controlled in such a way that, in both directions of motion, it accelerates to the speed v in a short acceleration section, moves with an approximately constant speed v in the abovementioned section and, in a subsequent retardation section, which in turn is very short as compared with the abovementioned section, brakes to a standstill. 
     The frequency f with which the slide  20  is moved to and fro by means of the drive  24 ′ is at least equally as high as the maximum frequency at which the objects  12  can occur, which is given by the quotient of the conveying speed v 1  and the permissible minimum distance A. The frequency f is advantageously approximately 1.2 to 4 times as high as the frequency defined by this ratio. 
     Fixed to the slide  20  at its one end is a bow-shaped contact element  30  of self-sprung design. Its free end extends approximately perpendicular to the conveying plane determined by the conveying device  10 . With the end region on this side, it projects forward, beyond the slide  20 , in the direction counter to the conveying direction  10  and is intended to rest and to slide with the free end on that flat side  12 ′ of the objects  12  which faces the counting device  16 , under a low spring prestress. 
     Also fixed to the slide  20 , at its one end, is a catch element  32 , which is likewise of self-sprung design and shaped like a bow. In its free end region, it has a hook element  34 , which is intended likewise to rest with its free end under spring prestress on the flat side  12 ′ of the objects  12  and to slide along the latter. As FIGS. 1 and 3 reveal, when it is in its rest position  36 , the contact element  30  extends forward in the conveying direction F with respect to the hook element  34 . In the contact position, which is indicated by dash-dotted lines in FIG.  2  and in FIG. 3, the contact element  30 , as viewed in the conveying direction, is located close to the catch element  32  and rests with a contact piece  38  fixed to it on a mating contact piece  38 ′ fixed to the slide  20 . The contact piece  38  and the mating contact piece  38 ′, forming a sensor element  39 , are connected via lines  40  to a counter  42 . Because the objects  20  are caught by the catch element  32 , the contact element  30  does not have to move back away in the direction of the conveying device  10 . 
     In the embodiment of the hook element  34  shown in FIG. 3, its catch face  44  is designed to be flat, while in the embodiment illustrated in FIG. 4, the catch face  44  of the hook element  34  is curved, so that the free end region of the hook element  34 , as viewed in the conveying direction F, pointing forward, can engage underneath the relevant object  12 , in each case from the rear edge  14 , and thus lift it into the hook element  34 . In the rest position  36 , the contact element  30  is located—in the conveying direction—close to the tip of the catch element  32 , in the contact position  36  at the bottom of the hook. 
     A reference roll  46  is freely rotatably mounted so as to be fixed in relation to the guide rail  18 ′. Led around said roll is a belt  48 , which runs further around a roll  50  which, in relation to the reference roll  46 , is arranged upstream and at a greater distance than the reference roll  46  from the conveying device  10 . Together with the conveying device  10 , the belt  48  forms an inlet for the overlapping formation S and prevents objects  12  being carried along by friction when an object  12  is gripped by the hook element  34  and displaced in the conveying direction F. For this purpose, the reference roll  46  is arranged upstream, at a short distance from the catch element  32  in the initial position  26 ′. 
     In the embodiment shown in FIGS. 5 to  7  as well, the conveying device  10  is constructed as a belt conveyor and is intended to convey the objects  12  in an overlapping formation S, in which each object  12  rests on the one respectively following, at the conveying speed v 1  in the conveying direction F. Located above the conveying device  10  is the counting device  16 , with the guide rail  18 ′ forming the guide means  18 . The slide  20  mounted on said guide rail is connected via the rod  22  to the piston/cylinder unit  24  which, as drive  24 ′, drives the slide  24  in exactly the same way as described further above in connection with the embodiment shown in FIGS. 1 to  4 . 
     The contact element  30  is fixed to the slide  20 . It is designed as a spring tongue, which is oriented with its free insertion end  52  in the conveying direction F and is intended to rest under spring prestress on the flat side  12 ′ of the objects  12  and to slide along the latter. On that side of the contact element  30  facing away from the conveying device  10 , a sensor element  54  is arranged. It is likewise designed like a spring tongue, fixed with the upstream end to the slide  20  and bent over in its downstream end region. In the region of the bent-over portion, the sensor element  54  rests on the contact element  30  and, together with the end region of the contact element on the insertion end, forms an inlet for the rear edge  14  of the objects  12 . The sensor element  54  is lifted by the contact element  30  when the contact element  30  is inserted into the object  12  or between two objects  12  and, in so doing, engaging under parts of the object  12  or the preceding object  12  in the end region  14 ′ of the latter, as shown by FIGS. 6 and 7. The contact element  30  forms an electric contact piece  38 , which interacts with the mating contact piece  38 ′ formed by the sensor element  54 . The contact element  30  and the sensor element  54  are likewise connected via lines  40  to a counter  42 . 
     Upstream of the bent-over portion of the sensor element  54 , a catch element  32 ′ is fixed directly to the contact element  30 , projects from the contact element  30  like a tongue in the direction of the slide and projects beyond the sensor element  54 . It is intended for its catch face  44  to come into contact with the rear edge  14  of an object  12  located between the contact element  30  and sensor element  54 , and to displace said object in the conveying direction F. 
     The apparatus functions as follows. The slide is driven, by means of the drive  24 ′, in and counter to the conveying direction F at a higher frequency F than the objects  12  occur. At the same time, in the case of the embodiments shown in FIGS. 1 to  4 , the hook element  34  of the catch element  32  and the free end of the contact element  30 , which is in the rest position  36 , and, in the case of the embodiment shown in FIGS. 5 to  7 , the contact element  30 , slide along the flat side  12 ′ of an object  12 . Because of the relative movement between the object  12  conveyed in the conveying direction F and the slide  20  moved counter to the conveying direction F, the hook element  34  and contact element  30  run off the object  12  at its rear edge  14  and come to rest on the flat side  12 ′ of the following object  12 . During the next stroke of the slide  20  in the conveying direction F, the slide  20  catches up with the relevant object  12  again and, in the case of the embodiment shown in FIGS. 1 to  4 , the contact element moves away from the rear edge  14  of the object into the contact position  36 ′ and, in the case of the embodiment shown in FIGS. 5 to  7 , the sensor element  54  is lifted off the contact element  30 . The signal produced at this time can be evaluated by the counter  42  for the purpose of counting. Then, during the further movement of the slide  20  in the conveying direction F, the catch element  32 ,  32 ′ takes the relevant object  12  with it. At the end of its working stroke, the slide  20  is braked, the object  12  then being conveyed onward at the conveying speed v 1  by the conveying device  10 , and the electric contact being opened again in the case of the embodiment shown in FIGS. 1 to  4 , and closed in the case of the embodiment shown in FIGS. 5 to  7 . This signal is also suitable to be evaluated by the counter  42 . In particular, with knowledge of the corresponding position of the slide  20  at a specific time, the precise location of the object  12  can be determined, which may be important for further processing. 
     This procedure is repeated for each object. Each object is displaced out of the active range of the counting device  16  and can therefore influence the counter only once. 
     The embodiment of the hook element  34  shown in FIG. 4 has the advantage over the embodiment shown in FIG. 3 of preventing a situation in which only the hook element  34  but not the contact element  30  can run off an object  12  since, as viewed in the conveying direction F, the free end of the hook element  34  and of the contact element  30  are arranged at the same level. 
     It is also conceivable, in an embodiment of the contact element  30  according to FIGS. 5 to  7 , to provide the contact element  30  with a reflector at its free end and to construct the sensor element as a light-source/light-sensor element, which can be arranged on the slide  20  or in a stationary position at the downstream end position  28  of the reflector. 
     The apparatus is also suitable for counting objects which arise in an overlapping formation in which each object rests on the preceding one. To this end, the counting device is arranged in mirror-image form to the embodiments shown, underneath the conveying device F, in such a way that the contact element and catch element project beyond the conveying plane.