Abstract:
A paper thickness measuring device for use in a rotary paper feeding device having a rotating cylindrical drum. In a preferred embodiment of the present invention, a gripper is mounted on the cylindrical drum for gripping a sheet; and a target is mounted on the cylindrical drum and mechanically linked to the gripper such that a position of the target corresponds to displacement of the gripper by a gripped sheet. The target is arranged and configured for detection of the target position a predetermined time or at a downstream location after the gripper grips a sheet.

Description:
BACKGROUND OF THE INVENTION 
     Modern mail room operations are arranged to process mass distribution mailings that may involve the mailing of many individual mail items, each containing one, two, three or more pages. The operation typically includes machines and devices to feed, fold, transport and insert pages into envelopes for eventual mailing. A rotary paper feeding device comprises a rotating cylindrical drum arranged to grip a number of pages for each mail item, for delivery to, for example a folding machine. In connection with the operation of the paper feeding device, it is desirable to measure the thickness of each item gripped by the device, to make certain that the proper number of pages is being delivered to the folding machine. 
     To that end, various mechanical devices have been provided on the rotating cylinder to press the gripped paper toward the cylinder drum to sense the thickness and thereby determine the number of pages being gripped by the rotating cylinder. The accuracy of the measurement is dependent upon mechanical action of a number of interconnected mechanical devices. 
     Another prior proposal for determining the number of pages gripped by the rotating cylinder comprises a sensing device in the rotating cylindrical drum to sense the thickness of the gripped pages. The sensing device then transfers the sensed data to a fixed receiving device mounted adjacent to the rotating cylinder. This arrangement requires the use of complex sensing equipment, and also involves an angular delay between sensing the thickness, and the transfer of the data to the fixed receiving device. 
     Thus, the known mechanisms for sensing the number of pages being feed to a device such as a folding machine have deficiencies that would be advantageous to overcome. 
     SUMMARY OF THE INVENTION 
     The present invention provides a new and improved paper thickness measuring device adapted to measure the thickness of a sheet being gripped and fed by a rotating cylinder drum of a rotary paper feeding device. 
     In a preferred embodiment of the present invention, a paper thickness measuring device is arranged for use in a rotary paper feeding device having a rotating cylindrical drum. A gripper is mounted on the cylindrical drum for gripping a sheet; 
     and a target is mounted on the cylindrical drum and mechanically linked to the gripper such that a position of the target corresponds to displacement of the gripper by a gripped sheet. The target is arranged and configured for detection of the target position a predetermined time or at a downstream location after the gripper grips a sheet. 
     In another preferred embodiment of the present invention, a rotary paper feeding device comprises a rotating cylindrical drum and a gripper mounted on the cylindrical drum for gripping a sheet. Pursuant to a feature of the present invention, a target is mounted on the cylindrical drum and mechanically linked to the gripper such that a position of the target corresponds to displacement of the gripper by a gripped sheet. The target is arranged and configured for detection of the target position a predetermined time or at a downstream location after the gripper grips a sheet. 
     In a further embodiment of the present invention, a method for measuring the thickness of a sheet being gripped by a rotary paper feeding device comprises the steps of providing a rotating cylindrical drum, providing a gripper mounted on the cylindrical drum for gripping a sheet such that the gripper is displaced upon gripping a sheet, and mechanically linking the gripper to a target mounted on the cylindrical drum to cause a position of the target to correspond to displacement of the gripper by a gripped sheet. The method includes the step of arranging the target for detection of the target position a predetermined time or at a downstream location after the gripper grips a sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a rotating cylinder for gripping and delivering paper pages and including a paper thickness measuring device according to an exemplary embodiment of the present invention. 
         FIG. 2  is a side view of the rotating cylinder of  FIG. 1  with a sheet gripped by the cylinder, and illustrating the operation of the paper thickness measuring device. 
         FIG. 3  shows a data output graph of the paper thickness measuring device, and indicating data for various numbers of gripped pages. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and initially to  FIG. 1 , there is illustrated a rotating cylinder drum  100  for gripping and delivering paper pages to a subsequent device (not illustrated). The drum  100  is rotatably mounted on a support shaft  102  for rotation in a preselected direction  104 . A seat structure  106  is mounted at a peripheral surface of the drum  100 . The seat structure  106  is arranged to provide a receiving surface for a sheet or sheets of material such as, for example, paper, to be delivered by the drum  100  to the subsequent device, due to the rotation of the drum  100 . 
     A rigid gripper element  108  is mechanically linked to a gripper arm  110 , that is, in turn, movably mounted to a shaft  112  received in the drum  100 . As shown in the exemplary embodiment of the present invention illustrated in  FIG. 1 , the shaft  112  is mounted in the drum  100  such that movement of the rigid gripper element  108  causes the gripper arm  110  to rotate about the shaft  112 . 
     In this manner, a sheet received upon the seat  106 , and moved laterally toward the edge of the gripper  108  is received under the edge of the gripper  108 . This results in movement of the gripper  108  away from the surface of the drum  100 , and causes a rotation of the gripper arm  110 , with the gripper  108  pinching down on the sheet for movement with the drum  100 , as will be explained in further detail with respect to  FIG. 2 . 
     Pursuant to a feature of an exemplary embodiment of the present invention, a linear slide  114  is mounted to the drum  100 . The linear slide  114  is arranged on the drum  100 , adjacent to the gripper  108  and gripper arm  110 , as shown in  FIG. 1 . Accordingly, the linear slide  114  rotates with the drum  100 . A linear bushing  116  is slidably mounted on the linear slide  114 . The linear bushing  116  is arranged to mount a curved target  118  for linear movement with the linear bushing  116  along the length of the linear slide  114 . 
     According to a further feature of the exemplary embodiment of the present invention, an intermediate arm  120  extends from the linear bushing  116  to a mechanical linkage  122  with the gripper arm  110 . The mechanical linkage  122  causes the linear bushing  116  to slide along the linear slide  114  via the intermediate arm  122 , when movement of the gripper  108  rotates the gripper arm  110 . 
     In this manner, the target  118  slides along the length of the linear slide  114 , as a function of the movement of the gripper  108 . The amount of movement of the gripper  108  is, in turn, a function of the thickness of the sheet received under the edge of the gripper  108 , as will appear. Thus, the position of the target  118  on the linear slide  114  represents the thickness of the sheet gripped by the gripper  108 . The position of the target  118  changes as and when a sheet is inserted under the edge of the gripper  108 . 
     In order to utilize the target position information as an indication of sheet thickness, a distance sensor  124  is arranged adjacent to the rotating drum  100 , in a position such that the target  118  passes beneath the distance sensor  124  a predetermined time or at a downstream location after insertion of a sheet under the edge of the gripper  108 , as shown in  FIG. 1 . The predetermined time between insertion of a sheet under the edge of the gripper  108 , and the passing of the target  118  beneath the distance sensor  124  is set to minimize any angular delay between the insertion of a sheet, and measuring operation of the distance sensor  124 , while assuring accurate operation. The distance sensor  124  can be mounted on a frame supporting the support shaft  102 , as is generally known in the art, and comprise, for example, a photo detector to measure the distance of the distance sensor  124  from the surface of the target  118  as it rotates past the distance sensor  124 . The distance sensor  124  is, therefore, mounted such that photo detector beams emitted by the distance sensor  124  are reflected off the surface of the target  118  as it rotates past the distance sensor  124 . 
     To advantage, the surface of the target  118  is curved to enable an accurate distance reading. The operation of the distance sensor  124  is synchronized to the rotation of the drum  100  so as to emit photo detector beams and receive reflections from the surface of the target  118 , as the target  118  passes the distance sensor  124  during rotation of the drum  100 . The distance sensor  124  operates to generate electrical signals as a function the time between emission and reception of the photo detector beams. As should be understood, the signal strength will be a function of the position of the target  118 , and therefore be proportional to the thickness of a sheet gripped by the gripper  108 . 
     In accordance with an exemplary embodiment of the present invention, the distance sensor  124  is coupled to a measuring device, such as a PC  126 . The PC  126  is programmed to receive and display the electrical signals received from the distance sensor  124 . 
     Referring now to  FIG. 2 , the rotating cylinder drum  100  of  FIG. 1  is illustrated with a sheet  126  gripped by the drum  100 . As shown in  FIG. 2 , the sheet  126  causes the edge of the gripper  108  to be displaced from the surface of the drum  100 , causing the gripper  108  to rotate the gripper arm  110  about the shaft  112 . The rotation of the gripper arm  110  pushes down on the intermediate arm  120 , which, in turn, displaces the linear bushing  116  along the length of the linear slide  114 . This action displaces the target  118  toward the support shaft  102 . 
     When the edge of the gripper  108  engages the surface of the drum  100  (see  FIG. 1 ), the target  118  is located at a position  200 , as shown in  FIG. 2 . This position corresponds to a “No Sheet” level or position. After displacement of the target  118  by action of the movement of the gripper  108  due to insertion of a sheet under the edge of the gripper  108 , the target  118  is located at another position  202 , which corresponds to a “Measured Sheet” level or position. The spacing  204  between the positions  200 ,  202  corresponds to the thickness of the sheet. 
     As described above, as the drum  100  rotates in the direction  104 , the target  118  periodically passes beneath the distance sensor  124 . The operation of the distance sensor  124  is synchronized to the rotation frequency of the target  118 . The distance sensor  124  emits a series of photo detector beams toward the target  118  when the target  118  is beneath the distance sensor  124 , and receives the reflections of the beams off the target surface. The distance sensor  124  measures the time it takes for the reflections to return, and translates that time into corresponding distance measurement electrical signals for transmission to the PC  126 . 
     As illustrated in  FIG. 3 , a data output graph shows representations of electrical signals generated by the distance sensor  124  as a function of the time between emission and reception of the photo beams. Each of the signals corresponds to the time between emission and reception of the photo detector beams. When the gripper  108  is resting against the surface of the drum  100 , the target  118  is at the No Sheet position  200 , and the distance sensor  124  generates signals  300  at a first signal level corresponding to a NO Sheet condition, while the target  118  passes beneath the distance sensor  124 . 
     When a single sheet of paper is inserted under the gripper  108 , the target is displaced to a Measured Sheet level  202  corresponding to generated signals  302 , at a second signal level representative of a single sheet of paper. 
     Similarly, when multiple sheets are inserted under the gripper, signals  304 ,  306 , at differing signal levels, are generated by the distance sensor  124 . The signals  304  correspond to two sheets of paper, while the signals  306  correspond to three sheets, and so on. 
     The signals illustrated in  FIG. 3  may comprise a display at the PC  126 . The PC  126  is programmed to display and process the signals  300 , 302 , 304 , 306  received from the distance sensor  124 . The PC  126  generates a visual display for a user, as illustrated in  FIG. 3 , and may also generate an alert or cause the drum  100  to stop operation when the number of pages measured is different from the number of pages meant to be delivered by the drum  100 . 
     A similar gripper-linear slide arrangement  400  can be mounted diametrically opposed to the gripper  108 , for gripping and measuring two sheets per rotation of the drum  100 . 
     In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.