Sheet stack separating device

Abstract

 A sheet-stack separating device is disclosed, which comprises means (3 to 7) for optically detecting the border of each sheet stack at the end wall of sheet pile (1), means (8 to 10) for raising the edge portion of the uppermost sheet stack for generating a gap between the uppermost and the next below stacks by impinging pressurized air onto the detected border portion, and sheet-stack separating head (8) for expanding and maintaining said gap by its insertion into said gap. Selectively, said means for optically detecting borders of sheet stacks may include means for optically sensing markers (3) applied to the end wall of each sheet stack of sheet pile, while said means for optically detecting borders of sheet stack may include means for generating video signals representing an optical image of the end wall of sheet pile; and means for counting border lines of individual sheets by using video signals before comparing the counted value against the predetermined value.

Description

Field of the Invention

[0001] The present invention relates to a device that splits a specific number of sheets from sheet pile for delivery to ensuing processes.

Background of the Invention

[0002] It is conventional warker's manual operation in the prior art to draw out a specific number of sheets from sheet pile cut in designated sizes in the preceding process and then deliver these sheets to the packing process, where the stack of the specific number of sheets are indiviclually packed prior to forwarding. However, such a sheet stack has relatively heavy weight, which normally ranges from 20 to 25 kilograms with 10 through 50mm of thickness for example, and as a result, operators are obliged to continuously follow up hard labor throughout working hours. Reflecting this, there is a growing demand for an early automation of the sheet-stack separation work. However, automation of such the operation for correctly dividing a specific number of sheets from the sheet pile involves considerable difficulty, and yet, there is fear of potentially damaging sheets themselves when performing such the automatic operation using mechanical means. As a result, acutually, any distinctly useful sheet-stack separating device has not yet been proposed, which should be capable of automatically and satisfactorily separating a specific number of sheets from sheet pile and delivering them to ensuing processes. For example, a prior art disclosed by the Japanese Utility Model Publication No. 47779 of 1980 features such a mechanism that causes a sheet stack on the uppermost position to be slightly raised by impinging air onto the position in the end-wall of sheet pile designated for splitting said sheet stack, followed by insertion of a separating board into a gap thus formed in that position. Although this device can prevent sheets from damage as a result of introducing pneumatic means, from the viewpoint of separating a specific number of sheets as a stack, this device still has such a possibility of causing a large difference to occur in the number of the separated sheets due to such the mechanism which impinges air onto a specific fixed position below the top surface of the sheet pile. Consequently, this proposed device cannot actually be applicable to such a case vequiving a rigid accuracy in the number of sheets that a desired number of divided sheets must be packed for delivery.

[0003] On the oter hand, a sheet marker paper between each sheet stack containing a specific number of sheets inserted during the cutting process provide convenience for factory operators for correctly separating the designated sheet stack from sheet pile. On the other hand, if the inserted sheet marker papers still remain when the separated sheet stack is packed, then the stack is unpacked and transferred to the printing press, the remaining sheet marker papers will also be sent inside of the printing press, thus eventually causing unwanted printing problem to occur in the printed effect. To prevent this, desirably, sheet marker papers should not be made available for the sheet-stack separation work.

Problems to be sholved by the Invention

[0004] As described above, any of the prior arts has not yet realized such a useful technique that can satisfactorily execute automatic separation of a specific number of sheets from sheet pile before these are delivered to ensuing processes. Accordingly it is an object of the present invention to provide a satisfactory solution of such existing problems mentioned above.

Summary of the Invention

[0005] The sheet-stack separating device according to the present invention optically detects either the applied marker on the end wall of the sheet pile, which was written or marked during the cutting process for identifying a specific number of sheets, or the edge line of each sheet on the end wall of the sheet pile, and then device correctly counts the number of sheets before detecting the border of the designated sheet stack containing a specific number of sheets, while the device then impinges air onto the detected border so that a gap can be generated at the detected border, and finally, the device inserts the wedge head into said gap in order that the designated sheet stack can be securely split from the remainder of sheet pile.

Brief Description of the Drawings

[0006] 

Figure 1 is the simplified perspective view representing one of the preferred embodiments of a device according to the present invention;

Figure 2 is the longitudinal sectional view of the head employed by the above embodiment of the device;

Figure 3 is the plan view of the head shown in Figure 2;

Figure 4 is the video picture view showing the end wall of the sheet pile viewed via the video camera;

Figure 5 is the time chart representing the marker image edge detect operation;

Figure 6 is the time chart in conjunction with the sheet number counting operation during the edge-detect mode employed by another preferred embodiment of the device according to the present invention;

Figure 7 is the principle diagram showing an example of means for forward and backward positioning operation of the head; and

Fingure 8 is the perspective view showing the simplified configuration of the sheet-stack separating device reflecting a still further embodiment of the present invention.

Detailed Description of the Preferred Embodiments

[0007] The Japanese Patent Application No. 43269 of 1984 filed by the same applicant as the present invention had proposed a method of applying markers on the end wall of sheet pile. The following description of the preferred embodiments specifically refers to such the case in which markers are visibly applied the end wall of sheet pile at such intervals corresponding to a specific number of sheets by employing such the method proposed by the abovecited Japanese Patent Application No. 43269 of 1984 or using any other means found appropriate. In Figure 1, the reference numeral 1 represents a sheet pile containig sheets that are preliminarily cut into a specific size, which is mounted on the table-lifter 2. The table-lifter 2 lifts the sheet pile 1 by such a height corresponding to the thickness of each sheet stack after the designated sheet stack containing a specific number of sheets has been removed from the sheet pile 1, thus allowing the upper surface of the sheet pile 1 to remain in the same height level constantly. The reference numeral 3 represents the marker line, while the bottom position of which matches the border of the upper and lower sheet stacks. The reference numeral 4 represents the video camera, which is mounted on the vertically movable table 5. The video camera 4 has an object lens 6 through which the image of marker 3 applied to the end wall of sheet pile 1 is produced to be focused on the two-dimensional image sensor 7. The reference numeral 8 represents the wedge-shaped head which is also mounted on said table 5 mounting the video camera 4 in order that the head 8 can freely move in the direction of either approaching or leaving the sheet pile 1, while the tip end the wedge head 8 is adjusted to a specific height indentical to the coordinate xo in the "x " or vertical direction on the image sensor 7 of the video camera 4. In other words, the height position relationship between the wedge head 8 and the video camera 4 is adjusted so that the image of the assumed contact line made by causing the assumed extension horizontally and forwardly from the tip end of the wedge head 8 to reach the end wall of the sheet pile 1 can be converted into the horizontal line of level xo on the image sensor 7. In conjunction with the image of maker 3 on the end wall of the uppermost sheet stack of sheet pile 1, table 5 mounting both the video camera 4 and the wedge head 8 is arranged so that it can vertically move within a narrow range centering such the height position at which the bottom edge of marker 3 exactly matches the line of of coordinate xo. The controller unit 9, while it vertically moves the table 5, scans the image sensor 7 to detect a specific height position at which the bottom edge of the image of marker 3 correctly matches the line of coordinate xo, and then causes table 5 to stop at this height positon. Next, the controller unit 9 causes the wedge head 8 to move forward up to the position at which the tip end of head 8 is extremely close to the end wall of sheet pile 1. As described above, since the image on the image sensor 7 is arranged to correctly match the line xo where the assumed extension of the tip end of the head 8 reaches sheet pile 1, the height position of the tip end of the wedge head 8 exactly matches the height position of border between the uppermost sheet stack of sheet pile 1 and the following sheet stack set below. The tip end of the wedge head 8 is provided with a plurality of air-jet holes 10. The controller unit 9 first draws the tip end of the wedge head 8 to a position close to the sheet pile 1, and then causes a plurality of air-jet holes 10 to impinge air onto the end wall of sheet pile 1 by applying about 2kg/cm^z of the pneumatic pressure. As a result, the end wall portion of sheet pile 1 is split into the upper and lower portions at the lower border position of the uppermost sheet stack, thus generating a gap between both portions. While air-jet holes continuously jets air from the tip end of the wedge head 8, the controller unit 9 causes the head 8 to move forward until it is eventually inserted into the gap thus generated so that the gap can be expanded. The controller unit 9 then activates pusher (not shown) for entry into the expanded gap so that the uppermost sheet stack of sheet pile 1 can be pushed to the left in the drawing. The controller unit 9 then drives the table-lifter 2 to lift the sheet pile 1 by such a height corresponding to the thickness of individual sheet stack so that one-cycle operation can be completed. The controller unit 9 repeats these serial operations described above in order to sequentially send out sheet stacks each containing a specific number of sheets.

[0008] Figuer 2 shows the longitudinal sectional view of the wedge-shaped head 8. It has the level bottom surface and the tilted upper surface, while a plurality of air-jet holes 10 horizontally pass through the wedge-shaped head 8 so that a plurality of apertures can be provided at the tip end of the wedge-shaped head 8, each having 2mm of the aperture diameter. Figure 3 shows the upper surface of the wedge-shaped head 8 provided with three air air-jet holes 3. Such air-jet means is not limited to holelike means, but slits each having an appropriate dimensions can also be made available. Figure 4 shows such visualized video signals generated as a result of the scanning operation performed by the image sensor 7. The reference numeral 3i represents the image of marker 3, whereas a number of horizontal lines 11 represent border lines of each sheet. The scanning operation is executed to draw the scanning line in the direction of "x" and displace the scanning line in the direction of "y". In other words, the scanning line in this system is in the vertical direction against any conventional television sets having their scanning lines in the horizontal direction. Figure 5 shows the video signals. Among these signals, y is the video signal moving along the scan lines that pass through y=ys, whereas pulsive waveforms in such signal represent the border of each sheet. The reference character y'o represents a video signal in one of the scan lines included in the range of coordinates from yo to yo + Δy containig image 3i shown in Figure 4. When table 5 descends its position, the bottom portion of image 3i gradually ascends relative to the descending movement of table 5 and then it momentarily transverses the assumed horizontal line xo. However if the table 5 descends at a speed sisnificantly slower than the scanning period, actually, a plurality of scanning operations may be executed in the range between yo and yo + 0 even when the bottom edge of image 3i substantially matches line xo. In Figure 5, period t of the image signal r present in the border of each sheet is determined by both the thickness of each sheet and the scanning period, and thus, period t remains almost constant. Since the video signal remains "High" in every scanning line for such a duration longer than said period t, the controller unit 9 then identifies that the scanning operation is underway in the portion denoted by yo +Δy, and during this period, the controller unit 9 generates such a pulse having the time width J (where t is greater than J) at the moment when the scanning point in the direction of x has just passed through the coordinate point xo. The controller unit 9 then awaits such the time at which video signal goes "High" at the moment when the scanning point has just passed through the coordinate point xo and also such the moment at which video signal goes Low at the fall of pulse M shown in Figure 5. When table 5 gradually descends its position, the bottom edge of image 3i that was initially present in such a position upper than the coordinate point xo also descends itself gradually, and as a result, video signal that initially remained "High" when the scanning point passed through the coordinate point xo, will still remain "High" after time J is past. As soom as the bottom edge of image 3i correctly matches line xo, video signal then goes "High" at the timing of line xo and then goes "Low" after time J is past. These operations are repeatedly executed while the scanning is still underway within a range from yo to yo + Δy. As a result, if these operations are performed repeatedly for three times for example, the controller unit 9 then identifies that the height position of the tip end of the wedge head 8 correctly matches the height of the bottom edge of marker 3 present in the end wall of sheet pile 1, and then stops table 5 from descending its position furthermore. By sequentially executing such operations described above, the system correctly detects the height position of the bottom edge of marker 3.

[0009] Next, the second preferred embodiment of the present invention is described below, From the structural viewpoint, the second embodiment employs the single-dimensional line sensor in place of the two-dimensional image sensor made available for the video camera 4 of the first embodiment shown in Figure 1, in which only the method of controlling the controller unit 9 differs from the first embodiment. The second embodiment does not need such markers at all, which were used in the first embodiment. In the second embodiment, the sheet stack separating device is to count the number of sheets themselves one by one and then detaches the designated sheet stack by applying pneumatic means as soon as a specific number of sheets to be included in the stack have been counted up. Referring to Figure 1 again, the sheet stack separating device of the second preferred embodiment is described below.

[0010] In this embodiment; the scale factor of the video camera 4 is arranged so that the thickness of each sheet stack is fully visible within the field of the camera view. When the initial cyclic operation is entered, the video camera 4 is set to the uppermost position, while the upper surface of sheet pile 1 is out of the visible range of the video camera 4. Although light source is provided adjacent to the video camera 4 for illuminating the end wall of sheet pile 1 so that the end wall of sheet pile 1 is visible in white, the space field above sheet pile 1 still remains dark when viewing through the video camera 4. As a result, as shown in Figure 6, such signals A generated during the initial scanning operation of the line sensor of the video camera 4 remains "High" throughout a scan period. Next, table 5 starts to descend its position. Then, the upper portion of sheet pile 1 gradually becomes visible in the upper view range of the video camera 4 due to presence of the upside-down image, and as a result, video signal generates such a waveform B shown in Figure 6. Note that such pulsive waveform portions r shown in Figure 6 denote the borders of individual sheets as mentioned earlier. When table 5 gradually descends its position, dark area b above sheet pile 1 gradually diminishes itself in the video signal waveforms B and C shown in Figure 6. The controller unit 9 counts the rising edge of signal r in each scanning operation and clears the counted value either in the end or the beginning of the scanning operation. Such the counted value gradually increases. Then, the controller unit 9 causes table 5 to stop its descending operation at the moment when the counted value of the rising edge of signal r up to the position U correctly matches the numerical value of a specific number of sheets. Then, the controller unit 9 causes the wedge head 8 to move forward to impinge air onto the end wall of sheet pile 1 as was done by the first preferred embodiment.

[0011] When impinting air against the end wall of sheet pile 1, better effect can be realized by setting the tip end of the wedge head 8 to the position as close to the sheet pile 1 as possible without coming into contact with the end wall itself. If the end wall of sheet pile 1 is perfectly perpendicular to the floor base in perfect straightness, the amount of the forward movement of the wedge head 8 can be predetermined at a specific value. Nevertheless, actually, the end wall of sheet pile 1 either inclines itself or slightly being irregular. Accordingly, it is necessary to provide adequate means for correctly detecting such distances between the video camera 4 and the end wall of sheet pile 1 and between the tip end of the wedge hand and the end wall of sheet pile 1. Figure 7 shows one of such distance detecting means. Typically, such distance detecting means is comprised of light source 12, diaphragm 13, semitransparent mirror 14, light- emitting lens 15, light-receiving diaphragm 16, and light-receiving element 17, respectively. Such distance detecting means is secured to table 5 at a specific position close to the wedge head 8. Table 5 is secured to the arm of a robot unit ( not shown) that is movable in all directions. Lens 15 is adjusted so that the image of diaphragm 13 can be formed in such a position slightly behind the perpendicular phase that passes through the tip end of the wedge head 8. If the end wall of sheet pile 1 is at such the position exactly matching the image of the aperture of diaphragm 13 through lens 15, light from light source 12 is collected onto the end wall of sheet pile 1, thus maximizing the luminance of image. The light-receiving diaphragm 16 is set to such the position symmetrical to diaphragm 13 relating to the semitransparent mirror 14. The image of the aperture of diaphragm 13 at the end wall of sheet pile 1 is focussed at the aperture of the light-receiving diaphragm 16, and thereby the amount of light passing through the light-receiving diaphragm 16 is maximized at this moment, the intensity of signals output from the light-receiving element 17 is also maximized. As a result, when such the position allowing the maximum putput from the light-receiving element 17 is correctly detected by slightly moving table 5 either in the forward or backward direction, the optical system of the video camera 4 is focussed on the end wall of sheet pile 1, thus making it possible for the system to correctly set the tip end of the wedge head 8 to such the position closest to the end wall of sheet pile 1 without causing it to come into contact with said end wall. When this operation is executed, it is not necessary to have the controller unit 9 activate such operations to first detect the border of a sheet stack and then move the wedge head 8 forward by a specific distance to allow its tip end to approach the end wall of sheet pile 1.

[0012] Figure 8 shows another preferred embodiment of the present invention, more particularly, it shows such unique means capable of precisely counting the designated number of sheets when handling such sheets whose individual border lines can hardly be identified even when operating video camera 4.

[0013] Air nozzle 18 is provided in the front portion of table 5, while this nozzle 18 is provided with slit-shaped air-jet apertures at its upper tip end so that air can be impinged against sheets in the end wall of sheet pile 1 at a predetermined upward angle. Said air nozzle 18 is selectively connected to either low-pressure source 20 or high-pressure source 21. Video camera 4 is installed to the rear-end portion of table 5 so that the video camera 4 can watch those sheets which are present in such a range from the center of the air-jet apertures of air nozzle 18 to the upper portion of sheet pile 1. The head 8 provided with a guide bar 8a on its bottom surface is installed between air nozzle 18 and video camera 4, while the head 8 itself is freely movable on table 5 and its tip end points at the end wall of sheet pile 1. Both the air-jet apertures and the tip end of the head 8 are precisely adjusted so that both can remain in such a height position substantially identical to each other. Note that Figure 8 shows such the status in which the system has already completed counting of the designated number of sheets, and therefore, the actual sheet counting operation begins with the top of sheet pile 1. Operations of this embodiment are described below.

[0014] First, the controller unit 9 activates the video camera 4 and takes in video signals generated by the image sensor 7 in the activated camera 4, at the same time, it sets the mode-select valve 19 to the low-pressure position 20 so that pressurized air can be blown out of the air-jet apertures of air nozzle 18 at a relatively low speed. Next, when table 5 descends itself at a specific speed, low-speed jet air causes the edge portions of sheets at the end wall region of sheet pile 1 to be sequentially split from the united sheet pile 1, thus generating a gap between individual sheet edge portions blown enough to allow the image sensor 7 to correctly identify borders of individual sheets. This enables the controller unit 9 to securely count the number of sheets.

[0015] As soon as the counted value exactly matches the predetermined number of sheets, the controller unit 9 stops table 5 from descending its position and then switches the mode-select valve 19 into the high-pressure position 21 so that high-pressurized air can be blown out of the air-jet apertures at high speed, thus permitting the gap to remain widely open between such the sheet matching the designated number and the following one. The controller unit 9 then activates the entry of guide bar 8a . into gap thus held open, while said guide bar 8a can freely move along the bottom surface of the head. Then, the head 8 is also inserted into said gap using the guide bar 8a as rail. As a result, a sheet stack is securely detached from the rest of sheet pile 1, which then awaits entry of pusher unit.

[0016] Note that such conditions including the posture angle, the shape of air-jet apertures of air nozzle 18 and the applicable pressure, i.e., either low or high-pressure means, are variable depending on the size and the designated number of sheets to be handled. A typical example of successful sheet-stack separating operation using the device embodied by the present invention is introduced below. The sheet-stack separating device according to the present invention proved to have correctly and satisfactorily detached and processed each sheet stack that contained 250 sheets each made of such an art paper having 127 g/m² of weight after applying 2.7 kg/cm² of low-pneumatic source and 3.5 kg/cm² of high-pressure source, which were connected to the slit-type air-jet apertures in three rows, while each aperture had lmmi width and 75mm length of dimensions and contained in such the air-nozzle which was positioned at such an angle 75° apart from the vertical end wall of the sheet pile for impinging specific pressurized air against it. Such the device comprised of the above configuration embodied by the present invention proved to have securely and stably processed all the sheet stacks that contained the predetermined number of sheets.

[0017] Note that if such a phenomenon of sheet-to-sheet sticking takes place due to the electrostatic effect, it is suggested that either ionized air or humid air can be applied for reducing electrostatic charge.

[0018] As is clear from the foregoing detailed description, the sheet stack separating device embodied by the present invention first detects the border of the designated sheet stack and the remaining sheet stacks laid in sheet pile, followed by impinging air onto the detached border to cause the designated sheet stack to be detached from the rest. This allows the system to correctly control the number of sheets contained in each sheet stack, and in addition, since borders between sheet stacks are correctly detected without applying mechanical contact means, all the removable sheets can be rarely damaged by such the unique separation work executed by the device embodied by the present invention. Furthermore, since no sheet marker paper is inserted between sheet stacks according to one of the preferred embodiments of the present invention, it will dispense with any additional facilities and excessive attention otherwise needed for operators throughout the sheet-stack removing operations using manual or any other means.

Claims

1. Sheet-stack separating device comprising;

means for optically detecting the border of each sheet stack at the end wall of sheet pile;

means for raising the edge portion of the uppermost sheet stack for generating a gap between the uppermost and the next below sheet stacks by impinging pressurized air onto the detected border portion; and

sheet-stack separating head for expanding and maintaining said gap by its insertion into said gap.

2. Device defined in Claim 1 wherein said means for optically detecting borders of sheet stacks includes means for optically sensing markers applied to the end wall of each sheet stack of sheet pile.

3. Device defined in Claim 1 wherein said means for optically detecting borders of sheet stack includes means for generating video signals representing an optical image of the end wall of sheet pile; and means for counting border lines of individual: sheets by using video signals before comparing the counted value against the predetermined value.

4. Device defined in Claim 1 wherein said means for impinging pressurized air onto the detected border positions of sheets includes air-jet holes or slits in the tip end of said sheet-stack separating head.

5. Device defined in Claim 1 wherein said means for optically detecting borders of sheet stacks comprises:

means for impinging relatively low-speed pressure ized air onto the end wall of sheet pile;

means for generating video signals designating status of the end wall of sheet pile after generating gap between each sheet by impinging pressurized air against said end wall; and

means for counting border lines of individual sheets by using video signals before comparing the counted value against the predetermined value.

6. Device defined in Claim 2 wherein said means for impinging low-pressurized air onto said end wall of sheet pile includes mode-select valve means having a low-pressure position and a high pressure position to concurrently make up said means for generating a gap between borders of sheet stacks by impinging pressurized air onto said border portion when it is connected to high pneumatic source after detecting the border portions of sheets.

Drawing