EP0958218B1 - Stack changing device - Google Patents

Abstract

In a non-stop stack changing device, remaining-stack bars are pulled from the stack area one by one and out-of-line in relation to each other. To this end, a pull/push drive is provided, which makes it possible to push the remaining-stack bars simultaneously into the grooves of a pallet carrying a sheet stack. Furthermore, the pull/push drive makes it possible to pull the remaining-stack bars in pairs from inside outwards out of the stack area. In addition, the remaining-stack bars can be pulled in a first and second sequence in accordance with this model. An individual motor drive is provided for this purpose, which operates interlockingly on each individual remaining-stack bar.

Description

The invention relates to a method according to the preamble of claims 1 and 2 as well a device according to the preamble of claims 8 and 9.

It is known to use devices for the in sheet feeders of sheet printing machines to provide automated batch changes. These can be computational Forms exist, so-called residual pile support devices, with thrust and Lift actuators are provided for horizontal and vertical movement. Such so-called non-stop stack changers are suitable during the printing of Sheets of paper, i.e. in the machine run, remnants of processed sheet stacks from a pallet provided with grooves, for example, and on one subsequently inserted new sheet stack again in the sheet feeder to discontinue. Known devices are characterized by large constructive and assembly costs and require special designs of the Sheet feeder. Furthermore, devices are used, the Remaining stack support device a rake engaging in the grooves of the pallet exhibit. This rake is new when the remaining stack is combined with the used sheet stack as a whole between the two stack parts remove. This entails high driving forces and demands that of the Interface closest arch of the stack very strong. Also are To provide retention means that prevent the stack parts from moving and stress the stack edges. In addition, the operation of the Sheet feeder itself severely disabled or even made impossible. The arc run is difficult to master when changing, so that again and again Waste sheets arise.

Devices have been developed that overcome some of the disadvantages described partially avoid.

DE 3931710 C2 describes a non-stop sheet feeder for Sheet rotation machines known. It has a residual pile support device, those below one leading from the sheet feeder to the sheet rotation machine Belt table is arranged. The residual stack support device has one closed frame on which non-stop rods are arranged, which as Piston rods of individual cylinders are driven by means of a pressure medium can and retractable in the grooves of a pallet carrying a sheet stack are. The non-stop bars are on both sides when retracted of the frame and are to be successively removed from the area of the sheet feeder be removed. Nothing is said about the order. Bridging the gap due to the non-stop rods between the main and remaining stacks an obstacle to a flawless continuous when stacking Processing.

DE 4203500 A1 discloses a method and a device according to the preamble of claims 1, 2 and 8, 9, respectively. In parallel to the sheet feeder and associated with it on the end face, it has an auxiliary stack support device as an independent structural unit. In it, individually drivable skewers are provided via a common drive, which are retractable into grooves in a pallet carrying a sheet stack. The drive has individual chain drives that can be coupled to the respective spits. Special constructive measures are necessary for the guidance and accessibility of the chain drives. The chain drives completely block the space in front of the sheet feeder so that it is not accessible.
When changing stacks, it is intended to remove the skewers from the stacking area when the main and remaining stacks are merged, first on the outside, then in the middle and finally in the area between the skewers that have already been drawn, so that the remaining stack is placed gently on the sheet stack should. However, this is only possible with the required accuracy for heavy materials such as metal arches.

Finally, DE 19520772 C1 describes a non-stop sheet feeder for Printing machines with retractable and extendable fork bars known. In this Feeders are on both sides of the stacking area transversely to the sheet transport direction movable units of fork rods are provided. The fork bars are connected to each other and together in grooves a stack of sheets carrying pallet retractable. From there, they can take over an auxiliary stack to bridge the period until a new sheet stack is fed. For preliminary approximation of the main and the remaining stack before the final one Unite the fork rods are rectangular in cross section and around one Longitudinal axis rotatable. The fork rods are initially in the upright position inserted orientation to carry the greatest possible load can. They are then turned 90 degrees to approximate them so that the main and residual stacks to each other to the value of the thickness of the narrower side approach. When twisting the fork rods, measures have to be taken to get one Avoid moving the bow closest to the fork rods. this has turned out to be almost impracticable in practice.

Furthermore, DAS 1095297 is a sheet feeder with several Stacking hoists known. It has a fork-shaped residual stack support device on, which is provided with insertable residual stack bars in the grooves of a pallet. The device enables a remnant of a stack of sheets to be taken over from the pallet for the continuous feeding of the sheets during a new sheet stack is inserted into the sheet feeder. The residual stacking device is with a separate hoist parallel to the main stacking hoist within the Sheet feeder connected so that the remaining stack can be raised continuously. The The working area of the residual pile carrier is restricted. The Remaining pile support device hinders access to the sheet feeder.

The aim of the invention is to improve the device for stack change so that the disadvantages described are avoided.

The object of the invention is to provide a device of the type mentioned improve that batch change in a simple and continuous manner is possible, whereby the sheet transport must not be disturbed and the sheets be spared during the change process, so that none due to the stack change conditional waste occurs.

The solution to the problem arises from the patent claims.

It is advantageous that independently movable support and spacer bars are provided in the device, which are drawn from the stacking area not at the same time, but with a time delay, to relieve the sheet material. In this case, a different height of the two rod types can preferably be provided, which produces a flowing settling movement of the rest of the stack on the stack of sheets.
in particular, the continuous removal of the remaining stack bars from the inside to the outside and in two stages enables the remaining stack to be deposited gently on the sheet stack. A speed profile influencing the stack approach in the drawing speeds between the individual bars should preferably be maintained.

Fig. 1

einen Bogenanleger in Seitenansicht,

Fig. 2

einen Bogenanleger in Draufsicht,

Fig. 3

eine Stapelwechselvorrichtung in Draufsicht,

Fig. 4

eine Stapelwechselvorrichtung bei der Übernahme eines Reststapels, und

Fig. 5

eine Stapelwechselvorrichtung während des Stapelwechsels.

The invention is illustrated below with reference to drawings. Here show:

Fig. 1

a sheet feeder in side view,

Fig. 2

a sheet feeder in top view,

Fig. 3

a stack changing device in plan view,

Fig. 4

a stack changing device when taking over a remaining stack, and

Fig. 5

a stack changing device during the stack change.

In Figure 1, a sheet feeder 2 is connected to a sheet processing Machine, for example shown with a sheet printing machine 1. in the Sheet feeder 2, a sheet stack S is used for processing. The Sheet stack S can by means of a main stack lifting device, which is not closer here shown is raised in time with the sheet processing. The bow of the Sheet stack S are separated at the top and the Sheet printing machine 1 fed in a sheet stream. In the sheet feeder 2 is For this purpose, a sheet separation device 4 is provided, which with a whole Number of diverse controls for format-dependent settings and for Settings of the supply with suction or blown air is provided. The Controls are used to coordinate the various functions of the Sheet separation device 4 on the need-based transport of the sheets from sheet feeder 2 to sheet printing machine 1. In sheet feeder 2 is still a residual stack support device 3 is arranged, that of the sheet-fed printing press 1 facing end of the sheet feeder 2 is assigned. The Remaining stack support device 3 is provided with a frame 6 in which Remaining stacking rods 7 are mounted to be longitudinally displaceable. By means of the frame 6 is the Remaining stack support device 3 suspended from a lifting device 5. The Lifting device 5 is only in its position here, but not indicated in details. The lifting device 5 is used to hold an auxiliary stack in the sheet feeder 2 and to be raised in time with the sheet processing. Therefore, the lifting device 5 is also controllable synchronously with the main stacking device. The lifting device 5 consists of vertical guide rails 8 connected to the sheet feeder 2, on which the frame 6 is guided and has, for example, lifting chains, by means of which the residual stack support device 3 can be raised or lowered.

In Figure 2, the sheet feeder 2 is shown in a view from above. To the Sheet feeder 2 closes in the direction of sheet travel indicated by arrows a so-called belt table 20, over which the one generated by the separation Sheet current to sheet processing machine e.g. the printing press 1 is transported. The position of the sheet separation device 4 is also shown in FIG Assignment to the rear edge of the sheet stack S can be seen. The orientation of the Remaining stacking bars 7 are shown in their arrangement in relation to the sheet feeder 2, only the two outer remaining stacking rods 7 are shown and the others are indicated with lines of action. The position shown is for example, the standby position before initiating a Change process or the waiting position outside the operating area of the sheet feeder 2. The remaining stacking bars 7 are within the Remaining pile support device 3 performed so that it is in the position shown Take up the horizontal position outside the area of the sheet feeder 2. The rest of the stack support device 3 with its frame 6 is by means of Guide rails 8 guided on the sheet feeder 2 and vertically movable. The Lifting device 5 is again only indicated in its position and is on the Top of the guide rails 8, for example on the frame of the Sheet feeder 2, grips from there on frame 6 of residual stack support device 3 and moves them up and down on the guide rails 8.

FIG. 3 shows a complete representation of the residual stack support device 3. The frame 6 is guided vertically on the guide rails 8. The rest of the stacking rods 7 in the form of supporting rods 7A and spacing rods 7B are guided in the frame 6 in a front support rail 9. A traction drive 11 for occasionally pulling the support rods 7A and spacer rods 7B is arranged on a rear mounting rail 10. The position shown is the waiting position. Furthermore, drives 12 are provided on both sides for the longitudinal displacement of the rear support rail 10 on guide rails 13 on the frame 6. The drives 12 determine the position of the rear mounting rail 10 at the rear end or within the frame 6. The front mounting rail 9 is firmly connected to the frame 6.
The support rods 7A or spacer rods 7B are of different heights. The support rods 7A are, for example, approximately twice as high as the spacer rods 7B. The term height means the expansion of the support rods 7A or spacer rods 7B perpendicular to the plane of extent of the residual stack support device 3. The effect of this measure is shown in detail in the following diagrams.

The support rods 7A and spacer rods 7B can be of the same length. In a preferred embodiment, the support rods 7A are longer than that Spacer bars 78. The support bars 7A are used to take over a remaining stack H first the load bearing and must be dimensioned accordingly, whereby the load is to be diverted into another suspension element (see Fig. 4).

The residual stack support device 3 is shown in operation in FIG. The support rods 7A, and the spacer bars 7B are by means of the drives 12 together with the rear mounting rail 10 advanced relative to the front mounting rail 9 and inserted in grooves of a pallet P carrying the sheet stack S. Front support rail 9 and rear support rail 10 are located with the traction drive 11 now parallel in front of the pallet P, the rest of a sheet stack S, the so-called residual stack H carries. The pallet P and the remaining stack H become not touched by the front mounting rail 9. The longer and higher Support rods 7A lie on a residual stack lifting rail 14 in the direction of sheet travel seen front end in the sheet feeder 2. This residual stack lifting rail 14 is coupled with a linear actuator and for supporting the support rods 7A and the lifting movement provided during production. The Remaining stack lifting rail 14 and the lifting device 5 are both with the Remaining stack lifting device of the sheet feeder 2 connected or at least so mechanically or control technically coupled with each other that they at Batch processing especially when merging the remaining stack H can be lifted synchronously with a new sheet stack S.

The relationship of the pulling movement to the device is shown once again in FIG clarified within the sheet feeder 2. The support rods 7A and Spacer bars 7B alternately lie in grooves of a pallet P (one on the other the webs between the grooves of the pallet P normally the sheet stack S has to be presented on top). The support rods 7A are on the Remaining stacking lifting rail 14. The same applies in the case shown to the inner ones Spacer bars 7B, which are only half the height of the support bars 7A. The The pulling process of the support rods 7A begins with those closest to the center of the stack thicker support rods 7A, which are drawn as a pair as shown. Doing so the auxiliary stack H slowly in this area on the thinner spacer bars 7B on. Pulling the thicker support rods 7A and subsequently the thinner ones Spacer bars 7B are fluid and always in close succession separated from each other. For this is a device for controlling the train movement intended. This can be directly in the train drive 11 for the support rods 7A or Spacer bars 7B can be integrated or via further control means on the Actuate the traction drive of each individual support rod 7A or spacer rod 7B.

It is essential that when the remaining stacking rods 7 are pulled, the inner remaining stacking rods 7 are pulled at a generally lower speed than the outer remaining stacking rods 7. This applies both to the supporting rods 7A and to the spacer rods 7B. This ensures that at the time of removal of the remaining stack bars 7 in the region of the center, ie when the remaining stack H begins to sink, there is only a slow lowering on the stack surface. The remaining stack H can thus be easily tracked with respect to the separating device and the transfer position to the belt table 20.
The speed of the inner remaining stack bars 7 can be reduced, for example, by half compared to the outer remaining stack bars 7. However, it is constant over the entire drawing time of a remaining stacking rod 7. Likewise, the speed of the remaining stacking bars 7 can be continuously increasing from the inside to the outside.

In a further embodiment of the method it can be provided to vary the starting times of the drawing movement of the individual remaining stacking bars 7. In this case, for example, the inner remaining stacking rods 7 should be slowly pulled in order to enable the adaptation processes when separating the sheets and when the sheets are transferred to the front edge of the stack on the belt table. However, since this results in a delay for the entire changing process, the pulling movement of the further remaining stacking bars 7 can start at a higher speed before the slow remaining stacking bars 7 are completely pulled in the middle. The principle of the retention-free removal of the remaining stack bars 7 should not be violated.
The variant of the offset use of the pulling movement can also be applied to the movement from the remaining stacking rod 7 to the remaining stacking rod 7, depending on the nature of the sheets. This results in a further reduction in the time for changing the stack while maintaining good stack quality.

The drives of the remaining stacking rods 7 are to be designed so that the The speed during the drawing process can be changed from rod to rod. This succeeds preferably by means of individual drive devices for the remaining stacking bars 7 but also a common for all remaining stacking rods 7 drive device however depending on the construction on the respective support rod 7A or spacer rod 7B can be coupled or in which the movement of the respective support rods 7A or Spacer bars 7B is successively released.

I. - Bei Erreichen einer Mindesthöhe des Bogenstapels S wird der Stapelwechselvorgang gestartet.

II. - Die Tragstäbe 7A und die Distanzstäbe 7B werden gemeinsam vom Gestell 6 aus in die Nuten der Palette P unterhalb des Bogenstapels S eingeschoben, wobei der Bogenstapel S an der Rückseite zur Reststapeltragvorrichtung 3 hin frei bleibt.

III. - Die Tragstäbe 7A werden von der Reststapelhubschiene unterfahren und angehoben bis der Reststapel H von den Tragstäben 7A getragen wird.

IV. - Die Palette P wird abgesenkt und aus dem Bogenanleger 2 entfernt.

V. - Der Reststapel H wird mittels des Hilfstapelhubantriebes kontinuierlich zur Vereinzelung der Bogen weiter angehoben.

VI. - Ein neuer Bogenstapel S wird in den Bogenanleger 2 eingesetzt und mittels des Hauptstapelhubes angehoben.

VII. - Bei Berührung der Oberseite des Bogenstapels S mit der Unterseite der Tragstäbe 7A wird der Ziehvorgang der Tragstäbe 7A eingeleitet.

VIII. - Die inneren Tragstäbe 7A werden mit einer ersten Geschwindigkeit zwischen Reststapel H und Bogenstapel S herausgezogen.

IX. - Die folgenden weiter außen liegenden Tragstäbe 7A werden mit einer zweiten, größeren Geschwindigkeit zwischen Reststapel H und Bogenstapel S herausgezogen.

X. - Der Reststapel H legt sich von innen nach außen kontinuierlich auf den Distanzstäben 7B ab.

XI. - Die Reststapelhubschiene wird frei, die Reststapeltragvorrichtung 3 übernimmt keine Last mehr, die verbleibenden Distanzstäbe 7B haben nur noch Steuerungsfunktion für die Stapelvereinigung.

XII. - Die inneren Distanzstäbe 7B werden mit einer ersten Geschwindigkeit zwischen Reststapel H und Bogenstapel S herausgezogen.

XIII. - Die folgenden weiter außen liegenden Distanzstäbe 7B werden mit einer zweiten, größeren Geschwindigkeit zwischen Reststapel H und Bogenstapel S herausgezogen.

XIV. - Der Reststapel H legt sich von innen nach außen kontinuierlich auf der Oberseite des Bogenstapels S ab.

XV. - Der Stapelwechsel ist beendet.

The batch change therefore takes place as follows:

I. - When a minimum height of the sheet stack S is reached, the stack changing process is started.

II. - The support rods 7A and the spacer rods 7B are pushed together from the frame 6 into the grooves of the pallet P below the sheet stack S, the sheet stack S remaining on the back to the rest of the stack support device 3.

III. - The support rods 7A are moved under by the residual stack lifting rail and raised until the residual stack H is carried by the support rods 7A.

IV. - The pallet P is lowered and removed from the sheet feeder 2.

V. - The remaining stack H is continuously raised by means of the auxiliary stack lifting drive to separate the sheets.

VI. - A new sheet stack S is inserted into the sheet feeder 2 and raised by means of the main stack stroke.

VII. - When the top of the sheet stack S touches the underside of the support rods 7A, the drawing process of the support rods 7A is initiated.

VIII. - The inner support rods 7A are pulled out at a first speed between the remaining stack H and the stack of sheets S.

IX. The following support rods 7A located further out are pulled out at a second, greater speed between the remaining stack H and the stack of sheets S.

X. - The remaining stack H is continuously deposited on the spacer bars 7B from the inside to the outside.

XI. The rest of the stack lifting rail becomes free, the rest of the stack support device 3 no longer takes on the load, the remaining spacer bars 7B only have control functions for stacking.

XII. - The inner spacer bars 7B are pulled out at a first speed between the remaining stack H and the stack of sheets S.

XIII. The following spacer bars 7B located further out are pulled out at a second, higher speed between the remaining stack H and the stack of sheets S.

XIV. - The remaining stack H is continuously deposited on the top of the sheet stack S from the inside out.

XV. - The stack change has ended.

The whole procedure has the advantage that the remaining stack H is the sheet stack S continuously approaching, so that no jump points when removing the Remaining stacking rods 7 arise, which affect the sheet separation or the Removal of the sheets from the sheet feeder 2 on the belt table 20 disturbing impact or even interrupt the operational process. This applies initially for constant tracking of the top of the stack against the Sheet separation device, where a distance within a Tolerance range must be observed. This also applies to the removal of Sheet after the separation, because at the front edge of the sheet stack S or Remaining stack H control means, e.g. a so-called bow flap are provided that release or block the sheet path to the belt table 20. Here too maintain a predetermined height tolerance so that the leading edge of the sheet Not removed by the pushing movement from the trailing edge of the sheet strikes and is compressed.

In a further embodiment it can be provided that not all of the remaining stack support rods 7 are used. In the case of very thick sheet materials which, due to their stability, sink only slowly into the space between the gap in the gap between sheet stack S and remaining stack H, which increases when the support rods 7A are pulled, the spacer rods 7B can be omitted. This speeds up the changing process since time is saved for pulling the spacer bars 7B.
Likewise, support rods 7A can be omitted in pairs in the middle of the stack, so that the auxiliary stack H is immediately lowered onto the spacer rods 7B there. The adaptation process on the stack surface with respect to the separating device can be supported by first slowly lowering the pallet P.
The corresponding remaining stacking rods 7 do not have to be removed for these measures. It is sufficient to decouple or block the corresponding drive means. Of course, these remaining stacking rods 7 are then not inserted into the grooves of the pallet P before the stack change.

The pulling movement is especially important for the last-mentioned applications of the individual remaining stacking bars 7 at different speeds important to ensure the continuous process of sheet separation.

Claims (11)

1. Process for automatic continuous changing of a sheet pile (S) in a sheet feeder (2) on a sheet processing machine with the residual pile carrier device (3) which contains residual pile bars (7A, 7B) for timely receipt of a pile residue from a pallet, for the interim continuous lifting of the residual pile (H) and its subsequent deposition on to a newly fed in sheet pile (S) moved adjacent the residual pile (H) from below, wherein the residual pile bars (7A, 7B) can be shifted into the pile region and at least staggered relative to one another can be removed again from the pile region, characterised in that the residual pile is taken over over its entire surface, in that the residualpile bars (7A, 7B) can be slid in common below the residual pile and that the residual pile is continuously approached to the sheet pile (S) in that the residual pile bars (7A, 7B) starting from the centre of the pile are retractable in pairs from the pile region progressively towards the outside to the side edges of the sheet pile (S) and that the speed of the residual pile bars (7A, 7B) in the middle of the pile is smaller than towards the pile side edges.
2. Process for automatic continuous changing of a sheet pile (S) in a sheet feeder (2) on a sheet processing machine with a residual pile carrier device (3) which contains residual pile bars (7A, 7B) for timely receipt of a residual pile from a pallet, for the interim continuously lifting of the residual pile (H) and its subsequent deposition on to a newly fed in sheet pile moved adjacent the residual pile from below, wherein the residual pile bars (7A, 7B) can be shifted into the pile region and can be removed again from the pile region at least staggered relative to one another, characterised in that the residual pile is taken over over its entire surface, in that a first part of the residual pile bars (7A, 7B) takes over the residual pile together at a first level, that the residual pile is continuously approached to the sheet pile (S), in that the first residual pile bars (7A, 7B) can be retracted from the pile region separately from one another from the middle towards the outside, and that the speed of the first residual pile bars (7A, 7B) in the middle of the pile is less than that towards the pile side edges, that the residual pile in this connection is deposited on to a further portion of the residual pile bars (7A, 7B) so that the residual pile, prior to unification with the sheet pile (S), is brought to a second level lying closer to the surface of the sheet pile (S), and that the residual pile is laid on to the sheet pile (S) in that the second residual pile bars (7A, 7B) separately from one another can be retracted from the centre outwardly from the pile region, and that the speed of the second residual pile bars (7A, 7B) is lower in the middle of the pile than towards the pile side edges.
3. Process according to Claim 1 or 2, characterised in that the pulling process of the residual pile bars (7A, 7B) is only introduced once the previously withdrawn residual pile bars (7A, 7B) are entirely withdrawn.
4. Process according to Claims 1 to 3, characterised in that the speed of each individual ones of the residual pile bars (7A, 7B) remains constant during its withdrawal process.
5. Process according to Claim 1 or 2, characterised in that the beginning of the retraction movement of each individual one of the residual pile bars (7A, 7B) is already introduced during the pulling process of neighbouring slower residual pile bars (7A, 7B).
6. Process according to one of Claims 1 or 5, characterised in that the speed of the inner residual pile bars (7A, 7B) amounts preferably to around half of the value of the outer residual pile bars (7A, 7B).
7. Process according to one of Claims 1 to 5, characterised in that the speed of the residual pile bars (7A, 7B) rises in accordance with a speed profile from the inner residual pile bars (7A, 7B) to the outer residual pile bars (7A, 7B).
8. Device for changing a sheet pile (S) in accordance with the process in Claim 1 in a sheet feeder (2) on a sheet processing machine with a main pile lifting device for lifting and lowering a sheet pile (S), with a sheet pile carrier device (3) which contains residual pile bars (7A, 7B) for timely receipt of a residual pile (H) and its transfer on to a newly fed-in sheet pile (S), wherein the residual pile bars (7A, 7B) are provided with drive means for generating a longitudinal movement staggered with respect to one another, in such a fashion that they can be inserted into the pile region and can be removed from there at least staggered with respect to one another, and a residual pile lifting device (5) for lifting the residual pile carrier device (3), characterised in that residual pile bars are constructed as carrier bars (7A) and as distance bars (7B) provided with a smaller thickness compared with the carrier bars (7A), that the drive means of the distance bars (7B) can be rendered stationary or uncoupled, and that drive means are provided by means of which the speed for the inner carrier bars (7A) can be adjusted to a lower value than for the outer carrier bars (7A).
9. Device for changing a sheet pile (S) in accordance with the process in Claim 2 in a sheet feeder (2) on a sheet treating machine with a main pile lifting device for lifting and lowering a sheet pile, with a residual pile carrier device (3) which contains residual pile bars (7A, 7B) for timely receipt of a residual pile (H) and its transfer to a newly fed-in sheet pile (S), wherein the residual pile bars (7A, 7B) are provided with drive means to generate a longitudinal movement staggered with respect to one another, in such a fashion that they can be moved into the pile region and can be removed from there at least staggered with respect to one another, and a residual pile lifting device (5) for lifting the residual pile carrier device (3), characterised in that residual pile bars (7A, 7B) are provided of differing thickness and that drive means are provided by means of which the speed for retraction of at least the inner residual pile bars (7A, 7B) can be adjusted to a smaller value than for the outer residual pile bars (7A).
10. Device according to Claim 8 or 9, characterised in that for each of the residual pile bars (7A, 7B), separate drive means are provided.
11. Device according to Claim 8 or 9, characterised in that common drive means are provided for all of the residual pile bars (7A, 7B), wherein the drive connection of the drive means to each of the residual pile bars (7A, 7B) can be individually linked or freed, and that the drive means are constructed for this so that for the individual residual pile bars (7A, 7B), differing speeds can be generated.

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