FR2506673A1 - ROTARY PRESS COMPRISING A SHEET FEEDER AND AT LEAST ONE PRINTER GROUP - Google Patents

Abstract

In a rotary printing machine, to which a sheet has to be fed in each case only during every second printing cylinder rotation, in order to guarantee that overlapping is always maintained on the sheet feeding table, activation of the initial grippers takes place in each case only in the second machine cycle. This causes the sheet resting at the front mark to be drawn off not immediately, i.e. during the next machine cycle, but only during the next but one machine cycle. However, it is ensured in the next but one machine cycle that the trailing end of a sheet overlaps the leading edge of the following sheet and thus uniform friction conditions are maintained.

Description

 The present invention relates to a rotary press comprising a sheet feeder and at least one printing unit to which the sheets to be printed can be fed in sheets by means of a margin table provided with front cleats and a clamp system preliminary, a sheet being printed in the printing unit only during a rotation of two of the printing cylinder.

 German patent application -P 31 08 806.6 describes a printing press of the kind specified above in which the pneumatic device which removes the sheets in the feeder is actuated by means of a control device such that a sheet is only entered for the first year in the press during a cycle of two leaves removal. In addition, the press described in this patent application offers the possibility of halving the speed of feeding the sheets by means of a speed change having a transmission ratio equal to 2: 1.

These two arrangements result in a sheet being presented to the preliminary clamps only when the printing cylinder is rotated in two. In such an operating mode of the press, the distance between the sheets fed in sheets necessarily increases, which ultimately leads to a sheet-by-sheet installation. This results from the fact that an arriving sheet is still several hundred millimeters away from the edge of the margin or from the front cleats when it is passed by the end of the previous sheet which is pulled into the machine by the preliminary clamps and the margin drum. Such a form of installation has the drawback that the various resistances due to friction between two superposed sheets, on the one hand, and, on the other hand, between the sheet and the margin table or the belts of the latter, produce an unfavorable effect. Another disadvantage is that this can lead to the formation of folds on the front edge of the next sheet when the rear part of the sheet which precedes it leaves the front area of this next sheet too soon or when, due to the arrival late on the next sheet, the latter can no longer cover it and, therefore, maintain it.

 The object of the invention, in a press of the kind specified above, is to make it possible to maintain the web long enough for each sheet to reach the front or margin cleats.

 According to the invention, this object is achieved thanks to the fact that each sheet which arrives against the front stops of the margin table during a cycle of the machine corresponding to a rotation of a printing cylinder can be brought to the printing unit. by the system of preliminary clamps during the next second cycle of the machine.

 The basic principle of the present invention is that a sheet arriving against the front cleats should not be driven immediately during the next movement of the preliminary clamps, but only during the second following movement. Such a shift of the active phases of the preliminary grippers is possible without difficulty when only one cycle out of two of the machine is carried out in the form of an active cycle, that is to say a supply cycle of leaf. This means that it is only during an active cycle of the machine that the grippers of the preliminary gripper system must grab a sheet and that the margin tabs must be erased by tilting. During the intermediate and inactive gripper cycle sheets, and according to the invention, no sheet must be brought to the first printing unit, and this is advantageously achieved thanks to the fact that the clamps of the preliminary clamp system remain open during the forward movement, that is to say say in the direction of the printing group, and that the margin tabs remain in the margin position, which means that they do not disappear by tilting downwards.

 The control of the entry of the sheet on the margin table or the prevention of this entry during the inactive cycles of the machine takes place, preferably, by means of a photoelectric cell with reflection whose detection point is located a few millimeters downstream of the arrival of each new sheet. Thus, the detection result can be processed within a time interval of less than 3600 and it can be used for the control of the preliminary clamps and the margin cleats.

 The description which follows, and which has no limiting character, will make it possible to understand clearly how the present invention can be put into practice.

It should be read against the accompanying drawings, among which:
- Figure 1 shows a rotary press in which the supply of sheets according to the invention can be used
- Figure 2 shows a diagram representing the movements of the leaves
- Figures 3 and 4 show a front cleat comprising a sheet detection device
- Figure 5 shows a preliminary clamp
- Figure 6 shows a control device for the preliminary clamp according to Figure 5
- Figure 7 shows a control and stop device for a front cleat.

 Figure 1 schematically shows an online sheetfed offset press which consists of a first printing group 1 and a second printing group 2 mounted downstream of the first. The sheets coming from a pile 3 which has been shown only partially are brought in tablecloth, or in scales, on a margin table 4 against margin or front cleats 5. A photoelectric cell with reflection 6 is mounted upstream of the front cleats 5. By means of a system of preliminary clamps 7, the sheets are then brought individually to the margin drum of the first printing group 1. In the printing groups 1 and 2, the sheets are provided with a double-sided printing, after which they are deposited in a conventional manner on a stack of sheets, not shown, by means of a chain output system 8.

On the diagram of FIG. 2, six cycles I to VI of the machine are represented on the abscissa, each going from O to 3600. The curve 9 of sinusoidal allurc situated above the axis of the abscissa represents the movement of the clamps preliminary to the during these six cycles of the machine, while the curve 10 corresponds to the tilting movements of the front stops 5. The ordinates, for the zone situated below the abscissa axis, represent the distance in millimeters to the front cleats 5 on the table or margin plate 4. In the area above the x-axis, the distance from the front cleats is plotted in the direction of the margin drum, also in millimeters. the sheet clamps and the tilting path of the front stops. The abscissa axis corresponds to the leaf stop line defined by the front stops 5
A sheet 11 which moves on the margin table 4 is delayed on its way to the front stops 5 by the conveyor belts, and its front edge reaches the front stops 5 around 1600 in cycle II of the machine. According to the invention, the sheet 11 is not gripped by the system of preliminary clamps 7 during cycle III of the machine, but only during its cycle IV, As can be seen in FIG. 2, the front edge of the sheet 11 is removed from the front cleats 5 in cycle IV of the machine, during the forward movement or the erasure by tilting of the preliminary clamps, after which the transmission to the margin drum takes place.

 For the displacement curves represented in FIG. 2, it should be noted that each of the curves designated by 11, 12 and 13 represents the front edge of each of the sheets 11, 12 and 13 respectively, while the corresponding rear edge is designated by it ', 12' and 13 'respectively.

 The sheet 11 which is withdrawn by its front edge from the front tabs 5 during cycle IV of the machine therefore moves further up to its rear edge 11 ′ on the margin table during this same cycle IV. The same is true for the corresponding subsequent sheets 12, 13 and their respective rear edges 12 'and 13'. In the representation of FIG. 2, we stick, for reasons of space, to the curve of the rear edge 12 ′. As can be seen in this FIG. 2, a sheet 11 arriving by its front edge during cycle II is not taken up by the system of preliminary clamps 7 during cycle III, contrary to what takes place in known machines , but only during cycle IV. The same applies to sheet 12, the front edge of which arrives during cycle IV and which is only removed from the margin table 4 during cycle VI. The front edge of the sheet 13 arriving during cycle VI also reaches the front stops 5 to about 1600. This sheet is then removed during a cycle VIII which could not be represented in the figure.

 As can also be seen in FIG. 2, a lateral cleat 14 is mounted on the margin table 4 upstream of the front cleats and at a distance of approximately 180 mm from the latter, and it is conventionally used for lateral positioning leaves.

 We will now describe, with reference to FIGS. 3 to 7, an advantageous possibility of controlling the supply of the sheets shown in FIG. 2. As has already been mentioned, a photoelectric reflection cell 6 is mounted upstream of the front cleats 5 and it directs from below a light ray on the sheet 11 which is on the margin table i or on a margin sheet which will not be referred to in more detail. This sheet reflects light in such a way that it falls on the light-sensitive surface of the photoelectric reflection cell 6 when the sheet 11 is immediately on cell 6. This generates a signal Y whose exploitation will be described below in detail.

 FIG. 4 corresponds to the phase during which the sheet which, in FIG. 3, still rests on the margin table i upstream of the front cleats 5, is pulled over these margin cleats 5. It This results in a greater distance between 1 photoelectric reflection cell 6 and the sheet 11, so that the reflected ray no longer meets the sensitive surface of the cell. This generates an error signal X, the operation of which will also be described below in detail.

The detection of the film which, according to FIGS. 3 and 4, takes place once inside each cycle I to
VI of the machine, is made at around 1350. The important point, with regard to the instant of detection, that is to say the command of the photoelectric reflection cell 6, is that this command takes place before the next sheet has reached the tabs of front 5 by its front edge. According to the invention, this makes it possible to detect the state represented in FIG. 3 during a cycle of the machine, which is for example cycle III, and to detect the state represented in FIG. 4 during the cycle next which is for example cycle IV. This means that during the cycle
III, the front edge of the sheet 11 which has reached the front lugs 5 to 1350 during the cycle It takes the position shown in FIG. 3 and that thus, according to the invention, this sheet is taken up by the clamp system preliminary 7 during the following cycle IV.

 The end 10 ′ of the sheet 10 which is no longer shown in the figure and which was previously taken up by the system of preliminary clamps during cycle II, still covers the photocell at 1350 during this same cycle II reflection 6, however that the front edge of the sheet 11 does not reach the front stops 5 until later in cycle II, ie around 1600, and therefore after the detection which is carried out during this cycle II.

 On the basis of this principle, the positions of the sheets represented in FIGS. 3 and k are thus detected alternately and, using the signals X and Y which result therefrom, the sheets are taken up again during the even rank cycles of the machine II, LV, VI, etc., by means of an appropriate control of the system of preliminary clamps 7 and the front cleats 5.

 FIG. 5 shows in somewhat more detail a side view of the preliminary clamp system 7 which is mounted on a shaft 15. The leaf clamps 16 are applied with the pressure which is necessary on the supports 18 by means of springs. compression 17. Each support 18 is fixed to a support 19 which also rests on the shaft 15.

 The leaf clamps 16 are integral with an axis 20, which allows the opening and closing of these clamps 16 to grasp or release the leaves to be passed.

 As seen in Figure 6, a control lever 21 is further mounted integral in rotation on the axis 20, and this lever, via a roller 22, follows the outline of a locking pawl 23. The latter can pivot around a stud 24 and it is subjected to the action of a compression spring 25 which presses it on a cam 27 by means of a roller 26 secured to the pawl in question. The cam 27 can move in the direction of the arrows at the rate of the cycles of the machine. For this purpose, a conventional type control device is used which follows a cam rotating in synchronism with the machine and which has not been shown in detail. Thanks to the back-and-forth movements of the cam 27 which take place in synchronism with the machine, the stop pawl 23 is raised with the same periodicity, which causes the control lever 21 to tilt and, consequently, a rotation of the axis 20. Thus, the sheet clamps 16 open during their movement towards the front stops 5, they grip the sheet when they have reached these front stops 5 and they finally transmit it to the drum margin.

 The locking pawl 23 has in its upper part a spout in which another pawl 28 laughs in engagement. This stop pawl 28 is mounted mobile in rotation on an axis 77 and it can pivot thanks to an electromagnet 29.

 If we suppose, for example, that in 1350 in cycle II of the machine, the preceding sheet: sheet 11 or L Delivered to the menine moment on the front edges 5, which corresponds to the case of the figure! s, tm logic control circuit 31, which is for example a microcomputer, generates a stop signal X. As has already been indicated, the front edge of the sheet 11 has not yet reached the photo cell - electric with reflection at this instant (1350). The stop signal X then excites the electromagnet 29, which causes the stop pawl 28 to pivot in an anticlockwise direction. Therefore, the lower spout of the stop pawl 28 engages with the upper spout of the locking pawl 23. When moving the cam 27 to the right, this prevents any downward movement of the locking pawl 23 under the effect of the compression spring 25. This means that the sheet clamps 6 can no longer close during the next cycle of the machine, and that the sheet which rests on the margin table 4 is not gripped and therefore not trained during the next cycle III.

 During cycle III of the machine, and at 1350, a new detection or excitation of the photoelectric reflection cell 6 takes place. As in FIG. 3, this operation detects the presence of the front edge of the sheet 11 against the front cleats 5. This generates a control signal Y which demagnetizes the electromagnet 29 when the cam 27 is to the left, which makes the stop pawl 28 rotate clockwise and releases the beak of the locking pawl 23.

 By virtue of the movement to the right of the cam 27 which then takes place during the cycle IV of the machine, the locking pawl 23 can tilt down under the effect of the pressure of the spring 25. By means of the roller 22 and the control lever 21, this causes the sheet clamps 16 to close, so that the sheet 11 can be grasped and transmitted to the printing unit 1.

 FIG. 7 represents the pivoting movement of the front cleats 5. The chronology of their control is identical to that of the preliminary clamps, in the sense that during each of the machine cycles during which the sheet clamps 16 are not do not close and, consequently, do not grab a sheet on the margin table 4, the erasure by pivoting of the front tabs 5 (see FIG. 7) in the opposite direction to that of the needles of a watch is found stop. A plurality of the front stops 5 shown in FIG. 7 can be rotatably mounted on an axis 32. The latter can pivot under the effect of a linkage which consists of a rod 33 and a lever 34 mounted pivoting on an axis 35. A roller 36 fixed to the lever 34 follows a cam 37 which rotates in synchronism with the machine. A tension spring 38 presses the roller 36 on the cam 37.

 A stop lever 39 (FIG. 8) is also mounted integral in rotation on the axis 35, and it can pivot with the lever 34 when the electromagnet 41 is de-energized by a control signal Y. Thus, the front cleats 5 controlled by the cam 37 can pivot, and therefore disappear.

If then a blocking signal X is generated in the manner described above during cycle IV of the machine, for example, the electromagnet 41 is excited by the logic control circuit 31, whereby the stop pawl 40 arrives in the pivoting area of the stop lever 39.

 This means that the lever 34 can no longer pivot at the rate of the cam 37, which prevents erasure by pivoting of the front tabs 5.

 It is easy to understand that, when the machine is started, that is to say when the first sheet is introduced, a retarder circuit must be present in the logic control circuit so that the first sheet introduced, according to the invention, is not removed from the margin table 4 during the next cyclical period, but only during the second following period. Consequently, an "artificial" closing signal should be generated for the first sheet. Otherwise, the odd machine cycles (I, III, V, etc.) would become "active" cycles.

 In the context of the invention, it is possible to introduce the sheets with a speed corresponding to that which would be necessary if the sheets were introduced during each cycle of the machine. With the operating and control mode according to the invention, it is however advantageous to introduce the sheets with a lower speed and, for example, with half the speed, as shown in FIG. 2. An increase in the speed would result in figure 2 by a steeper slope for the curves located below the abscissa axis. By hatching the areas between the front edge of a sheet (for example 11) and the rear edge of this sheet (11 ', for example), which has not been done in FIG. 2 so as not to harm its clarity, we can represent the time during which a sheet is on the margin table 4. If such hatching is carried out, in the same way, for the next sheet, for example between its front edge 12 and its edge rear 12 ′, it can be checked that the sheet of scaly leaves which it is desired to obtain can be constantly maintained on the margin table.

Claims (6)

- CLAIMS 1. Rotary press comprising a sheet feeder and at least one printing unit to which the sheets to be printed can be brought in tablecloths by means of a margin table provided with front cleats and a system of preliminary clamps , a sheet being printed in the printing unit only when the printing cylinder is rotated in two, characterized in that each sheet (11, for example) which arrives against the front tabs (5) of the table margin (4) during a machine cycle (II, for example) corresponding to a rotation of the printing cylinder can be brought to the printing unit (1) by the system of preliminary clamps (7) during the next second cycle ( IV, for example) of the machine. 2. Rotary press according to claim 1, characterized in that an optical and electronic detector (6) is arranged upstream of the front cleats (5) and generates, during a cycle of the machine (IV, for example) , a closing signal (x) to block the sheet clamps (16) of the preliminary clamp system (7) during the next machine cycle (V, for example) when, before the arrival of the next sheet (12 , for example) to the front cleats (5), the sheet (11) that the pliers (16) of the system of preliminary pliers (7) to bring to the printing unit (1) is pulled over the front cleats (5) . 3. Rotary press according to claim 2, characterized in that the optical and electronic detector (6) generates a control signal (Y) when only one sheet (11, for example) is on the margin table (k) during a cycle of the machine (III, for example), its front edge being against the front cleats (5).  Rotary press according to any one of Claims 1 to 3, characterized in that the sheet clamps (16) of the system of preliminary clamps (7) which can be operated in synchronism with the cycles of the machine (I to VI) , can be blocked by a system of pawls (23, 28, 30) actuated by an electromagnet (29) at the arrival of a closing signal (X), so that a sheet (11) resting on the margin table (4) is not entered during the next machine cycle (III, for example). 5. Rotary press according to claim 4, characterized in that, for actuating the sheet clamps (16), a control lever (21) provided with a roller (22) is mounted integral in rotation on the axis (20) of the pliers, this lever being able to pivot to open and close the leaf pliers (16) in synchronism with the cycles of the machine under the effect of a locking pawl (23) when a stop pawl ( 28) has been switched off by an electromagnet (29).  6. Rotary press according to any one of claims 1 to 5, characterized in that the closing signal (X) can excite another electromagnet (41) which can block the pivoting movement of the front cleats (5) via a system of closing pawls (39, 40).  7. A rotary press according to claim 6, characterized in that the closing pawl system (39, 40), upon arrival of the closing signal (X), blocks the pivoting of a linkage (33, 34) by via a control cam (37) which rotates in synchronism with the cycles of the machine (I to VI). 8. Rotary press according to any one of claims 6 and 7, characterized in that, for pivoting the front cleats (5), a closing lever (39) which cooperates with an actuated pawl (40) by an electromagnet (41) is mounted integral in rotation on a pin (35) on which is also mounted in integral rotationally a lever (34) of the linkage (33, 34) which follows the control cam (37) in being biased by a tension spring (38).