Patent Publication Number: US-7712603-B2

Title: Device for monitoring sheet products held together in a clamp

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for monitoring sheet products, in particular printed products, transported in a transport device by means of clamps. 
     A method and a device for monitoring pairs of sheet products bearing identification information, each transported in a clamp of a transport device, are known from the Swiss patent application with the application number 01276/05. As they pass a monitoring point, the products are subjected to an opto-electronic check with an image recording device. The images of the identification information recorded in this way are compared with given calibration images in an electronic further processing device. As a result of this comparison it is possible to determine whether the clamp was carrying the predetermined products. In the event of an error, control signals can be transmitted to downline processing devices so that a separate treatment of clamps holding the wrong products can be initiated. 
     In order to ensure high reliability in the recording of the identification information, it is necessary that this information always passes in roughly the same positions during the recording. In the above-mentioned patent application, this is ensured in that the identification information is contained on edge sections of each product in a side edge area of the products that is firmly gripped by the clamp jaws of the clamp. As the image recording device has to be located relatively close to the passing clamps during the recording of the identification information, positioning and installation problems can occur with some clamp transport devices due to the limited space available. An object is therefore to provide an improved monitoring device that allows the number of sheet products transported in a clamp to be monitored in the simplest and most reliable manner possible. 
     SUMMARY OF THE INVENTION 
     This object and others are achieved by providing a device for monitoring sheet products, in particular printed products, transported in a transport device by means of clamps in one transport direction, wherein the clamps are each intended to hold a first product and a second product simultaneously in a first side edge area in such a way that the products partially overlap one another and thereby form overlap-free edge sections, the device comprising at least two sensors, namely a first sensor and a second sensor, that are intended to generate signals on the basis of which the number of products held in the clamp can be determined, and wherein the first sensor is intended to generate a first detection signal referred to as reference signal when a clamp passes a reference area assigned to the first sensor, and the second sensor is arranged in such a way that it generates a second detection signal when at least one section of one of the products in a second side edge area free from the clamp passes through a detection area assigned to the second sensor. 
     The device according to the invention serves to monitor sheet products transported by means of clamps of a transport device in one transport direction. Pairs of at least partially overlapping products are gripped by a clamp in a first side edge area. The device is equipped with two sensors, whereby a first sensor is intended to generate a first detection signal referred to as reference signal when a clamp passes a reference area assigned to the first sensor. A second sensor is arranged in such a way that a so-called second detection signal is generated when at least one section of one of the products from a second side edge area free from the clamps passes through a detection area assigned to the second sensor. 
     The arrangement in which the second sensor is oriented to the free second side edge area avoids a possible spatial obstruction of the transport device moving the clamps. In addition the installation, maintenance and adjustment work for the second sensor can be reduced with this arrangement. 
     Compared with the prior art it is furthermore possible to waive identification information on the products and to use particularly inexpensive sensors, for example single-cell photodetectors instead of image recording devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a side view of a first embodiment of a monitoring device according to the invention equipped with three sensors; 
         FIG. 2  is a side view of a further embodiment of the monitoring device according to the invention with two sensors, whereby the second sensor in the transport direction is arranged downline of a deflection element; and 
         FIG. 3  is a diagram of a detection signal of the second sensor shown as a function of the signal size U and the time t for the embodiment shown in  FIG. 2  when two completely filled clamps each with two sheet products pass the detection area assigned to the second sensor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
       FIG. 1  shows in a side view diagrammatically a section of a transport device  10  in which clamps  12  (of which only one is shown) are arranged spaced behind one another on a transport organ  14 . The transport organ  14  can, for example, be designed as a conveyor chain or as a conveyor belt. It is driven in a transport direction F at a transport speed v. Alternatively it is naturally also possible that the clamps  12  are arranged, for example, on rail-guided carriages whose movement is supported in particular also sectionally by the force of gravity. 
     The clamps  12  have a clamp mouth  16  that can be opened and closed by mechanical actuation. A leading first printed product  20  and a following second printed product  22  traveling in transport direction F are held together in the clamp mouth  16  between two clamp jaws  18 . The printed products  20 ,  22  can be, for example, folded printed products such as newspapers and magazines, but also other single or multi-layer sheet products. 
     The printed products  20 ,  22  lie partially overlapped while forming overlap-free edge sections  24 . In the embodiment shown in  FIG. 1 , the following second printed product  22  in transport direction F is closer to the root  26  of the clamp mouth  16  than the leading first printed product  20  in transport direction F. Alternatively it is also possible that the leading first printed product  20  in transport direction F is closer to the root  26  of the clamp mouth  16  than the following second printed product  22  in transport direction F. As a result of the clamping of the two printed products  20 ,  22  in the clamp mouth  16 , a first side edge area  28  extending from the free ends of the clamp jaws  18  in the direction of the root  26  of the clamp mouth  16  on the two printed products  20 ,  22  is gripped firmly. In the embodiment illustrated, the first side edge area  28  is essentially formed by fold-side sections of the printed products  20 ,  22 . 
     A second side edge area  29  lying opposite the first side edge area  28  encompasses the free, to a certain extent also freely moving, end sections of the printed products  20 ,  22  including an overlap-free edge section  24  of the first printed product  20 . 
     Three stationary sensors, namely a first sensor  32 , a second sensor  34  and a third sensor  36  are arranged at a monitoring point  30 . The first sensor  32  is a so-called “clamp sensor” and monitors an assigned reference area  38  represented by the dot-dashed line extended from it. As soon as a clamp  12  passes this reference area  38 , the sensor triggers a first detection signal referred to as reference signal. This reference signal is transmitted further to an evaluation circuit  39  and serves to trigger a predetermined time interval during which a so-called second detection signal of the second sensor  34  and a so-called third detection signal of the third sensor  36  are detected. 
     The first sensor  32  can naturally thereby also be located at a greater distance upstream (relative to the transport direction F) of the second sensor  34  and the third sensor  36  than that shown in  FIG. 1 . In this case the predetermined time interval preferably starts at a later point in time after the passage of the clamp  12  that has been determined in relation to the distance of the first sensor  32  from the second and third sensor  34 ,  36  and to the transport speed v. 
     The second sensor  34  is arranged such that its assigned detection area  40  is oriented to the second side edge area  29  that lies opposite the clamp  12 , in particular to the lower overlap-free edge section  24  of the first printed product  20 . With such an arrangement of the second sensor  34  below and distant from the transport organ  14 , its installation and adjustment are very simple and possible with good accessibility. 
     If the overlap-free edge section  24  of the first printed product passes through the detection area  40  of the second sensor  34  within a time interval triggered by the reference signal of the first sensor  32 , the second detection signal of this sensor  34  will be transmitted to the evaluation circuit  39  and the presence of the first printed product  20  registered. Should the overlap-free edge section  24  not pass the detection area  40  within the triggered time interval, no second detection signal will be transmitted to the evaluation circuit  39 , and on expiry of the time interval the evaluation circuit  39  registers that the first printed product  20  was not present. The evaluation circuit  39  can then transmit control signals to downline processing devices so that special treatment of the clamp  12  not holding the first printed product  20  can be initiated. 
     In order to detect the presence of the second following printed product  22  in transport direction F, the third sensor  36  is oriented in such a way that its detection area  42  monitors the overlap-free edge section  24  of the second printed product  22  in the first side edge area  28 . By analogy with the function of the second sensor  34 , the third sensor  36  also transmits the third detection signal to the evaluation circuit  39  as soon as the second printed product  22  passes the detection area  42  within the triggered time interval. If the second printed product  22  is not detected because, for example, the second printed product  22  has not passed through the detection area  42  or the printed products  20 ,  22  are lying completely on top of one another at the position of the first printed product  20 , an error will again be registered by the evaluation circuit  39  in this case and corresponding error handling procedures initiated. 
       FIG. 2  shows a further embodiment of the monitoring device according to the invention. In the section of the transport device  10  around the monitoring point  30  shown, two clamps  12  with a first printed product  20  and a second printed product  22  respectively lying on top of one another and at least partially overlapped to form overlap-free edge sections  24  are illustrated. By contrast with the embodiment shown in  FIG. 1  in which either the following printed product  22  or the leading printed product  20  can be arranged closer to the root  26  of the clamp mouth  16  without the function of the monitoring device being impaired, it is essential with the embodiment shown in  FIG. 2  that the leading first printed product  20  in transport direction F extends further into the clamp mouth  16  than the trailing second printed product  22 . 
     With this embodiment, too, the first sensor  32  detects the passage of a clamp  12  through its reference area  38  and transmits its reference signal to the evaluation circuit  39 , thereby triggering a time window in which second detection signals generated by the second sensor  34  can be registered. In this embodiment, a ramp-like deflection element  44 , for example in the form of a supporting plate, is assigned to the second sensor  34 . 
     The detection area  40  of the second sensor  34  extends as seen in transport direction F in the shadow of the deflection element  44 . As the clamps  12  with the printed products  20 ,  22  approach, the second side edge area  29  of the printed products  20 ,  22  slides onto the deflection element  44 . On passing a rear (as seen in transport direction F) deflection element edge  46  of the deflection element  44 , the section of the first printed product  20  assigned to the second side edge area  29  swings through the detection area  40  of the second sensor  34 . If the first printed product  20  is present and held in the correct position in the clamp  12 , this is detected by the second sensor  34  which transmits a corresponding second detection signal to the evaluation circuit  39 . 
     The second printed product  22  initially still sliding along the elevated deflection element  44  during the passage of the first printed product  20  through the detection area  40  of the second sensor  34  also swings through the detection area  40  of the second sensor  34  after passing over the deflection edge  46 , thereby triggering a second detection signal for transmission to the evaluation circuit  39 . If the evaluation circuit  39  does not register the two corresponding, temporally offset second detection signals of the second sensor  34  within the triggered time interval, for example because only one printed product  20 ,  22  was present in the clamp  12  or the printed products  20 ,  22  were lying completely on top of one another, an error state will again be detected and corresponding error handling procedures initiated. 
     With both embodiments of the monitoring device according to the invention described, it is possible to determine whether neither of the printed products, or just one or both of the printed products  20 ,  22  were present in a clamp  12  transported past the monitoring point  30 . If only one printed product  20 ,  22  was present, then it is also possible to determine which printed product  20 ,  22  was missing and which was present, in the embodiment shown in  FIG. 1  on the basis of the assignment of the detection signals to one of the sensors  34 ,  36  and in the embodiment shown in  FIG. 2  on the basis of the time of the detection. 
     The diagram in  FIG. 3  shows for the second detection signals of the second sensor  34  the signal size U as a function of the time t for the passage of two clamps  12  with a first printed product  20  and a second printed product  22  respectively past the monitoring point  30  for the embodiment of the monitoring device according to the invention shown in  FIG. 2 . The signal curve shows two double peaks offset from one another by a time difference T, whereby the earlier smaller signal peak in each case is to be assigned to the passage of the first printed product  20  through the detection area  40  of the second sensor  34  and the later larger signal peak in each case to the passage of the second printed product  22  through the detection area  40  of the second sensor  34 . 
     The time difference T between the respective earlier and later signal peaks corresponds at least roughly to the quotient of the distance between the clamps  12  and their transport speed v, insofar as the two parameters remain constant between the passage through the detection area  40 . The time interval W also plotted in the diagram indicates a time window triggered by the reference signal during which the second detection signals of the second sensor  34  are expected with complete filling of the clamps with printed products  20 ,  22  and during which they are acquired or taken into consideration by the evaluation circuit  39 . 
     The signal sizes of the signal peaks assigned in each case to the first printed product  20  and the second printed product  22  respectively differ, as due to the mutually offset position of the printed products  20 ,  22  sections of the detection area  40  of the second sensor  34  of different size are covered by the printed products  20 ,  22 . Conversely, the signal size allows the holding of the printed products  20 ,  22  in the correct position in the clamps  12  to be assessed. 
     The sensors  32 ,  34 ,  36  are preferably designed as very inexpensive, contact-free, optical sensors, for example optical proximity sensors, light barriers, etc., or as mechanical sensors. However, the use of image recording devices such as digital cameras with recording being triggered after the clamp passage or continuously during a triggered time interval as sensors  32 ,  34 ,  36  is also possible. In particular the first sensor  32  for detection of the clamps  12  can, however, also be designed as a mechanical, capacitive or inductive proximity switch. 
     In practice, both the reference area  38  and the detection areas  40  and  42  frequently do not have a linear form and may have a spatial range, depending on the sensor type used. The fact that the reference area  38  or the detection areas  40 ,  42  also detect overlapping sections of the printed products  20 ,  22  during the detection of the passage of overlap-free edge sections  24  of the printed products  20 ,  22  has no major significance for the monitoring device according to the invention, but can—as already mentioned above—also be used to determine whether the printed products are held in the correct position in the clamps. 
     Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.