EP0036496B1 - Device for the lateral adjustment of sheets automatically conveyed to printing machines - Google Patents

Description

The invention relates to a device for the lateral alignment of automatically fed sheets on printing presses, in particular high-speed offset machines, in which the sheet is pressed by a swab roller or segment which is arranged in a swinging manner on a stationary drawing mark housing and is moved back and forth on a sliding plate serving as a pulling shoe, and through this against the stop of the side mark is draggable.

Draw marks on sheet-fed printing machines are known to have the task of precisely aligning the sheet arriving from the feeder laterally. This alignment must be carried out with the utmost precision, since alignment differences can cause color differences between the specimens. In order to achieve an optimal alignment, the sheet must therefore be able to be pulled exactly against a stop, avoiding compression at the stop. The result of this is that the pulling force has to be adjusted to the size of the arch, its thickness, its weight and the friction depending on the surface properties.

From DE-Patent 1015009 a device for the lateral alignment of automatically supplied sheets on printing presses is already known, which operates purely mechanically, a swab roller pressing the sheet onto a slide that can be moved back and forth transversely to the transport direction of the sheet. This slide, also called a drawing sheet, can e.g. according to the required friction with a different surface, i.e. rough, fine or smooth. Furthermore, in this known device, the swab roller contact pressure on the sliding plate can be changed by changing the spring preload or by replacing a spring. In the case of high-speed printing machines in particular, there is only a very short time available for the alignment process, which is why high acceleration values are required for the lateral sheet movement. While the setting is relatively unproblematic with strong print media, with thin papers it is difficult to measure the force setting of the drawing mark and its friction in such a way that on the one hand the print media experiences the specified acceleration and on the other hand it immediately starts to slide after reaching the stop, to avoid crushing the bow. This difficulty lies above all in the fact that the sheet to be aligned has to be accelerated from the idle state, which is why the highest possible initial acceleration would be necessary. These relationships are the reason why the known drawing marks do not work with sufficient accuracy and security, especially with extremely high sheet throughput per unit of time.

From the patent specification DE-C-617605 an alignment device for the lateral alignment of supplied sheets on printing machines is also known, wherein a sliding plate serves as a drawing shoe, pulls the sheet against a stop and has suction openings via which suction air can be fed, the time of supply of which with the pulling movement the sliding plate is synchronized and the suction effect is adjustable.

The object of the invention is therefore to improve the device defined by DE-C-1015009 for the lateral alignment of automatically fed sheets in order to enable both an individual force setting and a high acceleration of acceleration of the sheet to be aligned, with no replacement of mechanical parts more should be required.

This object is achieved in accordance with the characterizing part of patent claim 1. Advantageous further developments result from the subclaims and from the description in conjunction with the drawing.

From DE-Auslegeschrift 1278449 pneumatically working devices for lateral alignment of sheets are known per se, in which the sheets to be aligned are pulled against a stop by means of suction slides which can be displaced transversely to the sheet conveying direction. In such devices, however, the suction air acts continuously throughout the alignment process, so that, similarly to the purely mechanical devices, the acceleration process cannot be additionally supported. In addition, the sheets to be aligned do not completely cover the suction nozzles, particularly in the case of thin papers, and the time required for the alignment process becomes too long in the case of strong papers with a smooth surface.

In the device according to the invention, on the other hand, the swab roller ensures that the sheet to be aligned is pressed onto the suction openings in the sliding plate and these can thus be closed exactly. A significant advantage of the device according to the invention is the possibility of having the vacuum supporting the acceleration process act in a time-defined manner, so that the relatively high static friction or the moment of adhesion can be overcome quickly in the sheet resting state and that the sheet is compressed at the stop by switching off the suction air in good time is avoidable. There is also the option of lifting the swab roll before reaching the stop. The vacuum support in the first phase of the pulling process also enables a reduction in the mechanical setting forces, which additionally suppresses or reduces the risk of bow compression at the stop. In the device according to the invention, it is no longer necessary to coordinate the pressing force of the plucking roller and the roughness of the surface of the sliding plate so sensitively, since the end of the drawing process can be carried out with a significantly lower tensile force.

The invention is described in detail below using an exemplary embodiment, reference being made to the accompanying drawing.

In the drawing, a side pull mark 1 is shown on the right side of a feed table, not shown. A sheet to be aligned is transported approximately perpendicular to the plane 23 of the drawing against a front mark, not shown. The right edge of the sheet passes below a swab roller 3 which extends through a shell 2. The swab roller 3 is rotatably mounted on a swab roller lever 4 which can be pivoted about an axis 5.

By means of a compression spring 6, the pressure exerted by the swab roller 3 on a sheet to be aligned can be preset. Above the sliding plate 8, a shell 2 which can be adjusted in terms of distance by means of an adjusting screw 7 to adapt to the sheet thickness to be processed is shown. The contact pressure of the swab roller 3 can be varied by turning a threaded sleeve 19. In order to keep this setting fixed, a nut 20, which is rotatably arranged on the threaded sleeve 19, is counter-countered. In the latter, a spring rod 18 is guided on which the compression spring 6 is arranged.

A curve 15 is firmly attached to the spindle 25 synchronized with the sheet transport device, so that it rotates with the spindle 25. A roller 14 runs on the curved path of curve 15, which causes a swiveling movement of the swab roller lever 4 according to the curve shape about the axis 5 via a guide lever 16 when the spindle 25 rotates. As a result, the swab roller 3, which is supported in the swab roller lever on a head pin 21, is pressed against an arc located between the shell 2 and the sliding plate 8 in the same rhythm.

The spindle 25 also carries a further curve 22, which is connected to the curve 17 via a guide bush 17 and can be fastened by screws 27 to the guide bush 17 provided with slots. The curve stroke and the length of the curve stroke of curve 22 define the control range for the drawing operation, which can be shifted by turning curve 22. A roller 11 runs in curve 22, which is connected to a slide 29, so that turning the curve causes a left-right displacement of the slide 29 guided on guide rollers 12 and 24 at right angles to the sheet travel. The sliding plate 8 is fixed on the slide 29 by at least one fastening screw 9.

Due to the arrangement of the rotatable curves 15 and 22 on a common spindle 25 synchronized with the sheet transport, the shape of the curve regions makes it possible to coordinate the time at which the swab roller 3 touches the sliding plate 8 with the pulling movement of the sliding plate 8, so that the sheet located with its right edge between the swab roller 3 and the sliding plate 8 can be pulled against a right stop 28.

The setting of the curve 22 by twisting on the guide bushing 17 is facilitated by the use of a setting mark 26, the screws 27 connecting the curve 22 to the guide bushing 17 having to be loosened for the setting process.

The sliding plate 8 has suction openings 30 which can be acted upon by suction air via a vacuum chamber 31. Air is sucked out of the vacuum chamber 31 via a connecting piece 32 and a flexible line 33. The flexible line 33 is connected to a control valve 34, with the aid of which the vacuum conducted via a line 35 can be timed. The strength of the vacuum can be adjusted by a pressure reducing device 36. The vacuum is generated via a suction line 37 with a vacuum source, not shown.

At least one clock disk 38 is arranged on the spindle 25 or another single-speed shaft. By loosening the fastening screws 39 and 40, the clock disk 38 can be brought into the desired circumferential position and then fixed. The clock disc 38 has a circumferentially extending recess between the control edges 41 and 42. This recess extends over the area during which the suction air is to take effect.

Above the control disk 38, a sensing element in the form of an electrical sensor switch 43 is shown schematically, which can be fixed at a suitable point on the system table. The switch 43 encompasses the clock disk 38 with its legs 44 and 45 and generates when the first control edge occurs, e.g. 41 until the appearance of the second control edge, e.g. 42, an electrical signal by means of which the suction air supply to the suction openings 30 in the slide plate 8 in the control valve 34 is released. During the rest of the time, i.e. during the remaining rotational movement of approximately 330 °, the control valve 34 blocks the suction air supply to the suction openings 30. This blocking can be effected in a known manner by interrupting the supply path or by establishing a connection to the atmosphere, through which the vacuum breaks down.

The vacuum supply via the control valve 34 to the suction openings 30 coincides with the initial pulling movement of the sliding plate 8 which interacts with the swab roller 3, so that the sheet to be pulled against the stop 28 is accelerated very quickly, with the swab roll 3 the sheet in each case against the Suction openings 30 is pressed so that they can be completely covered and no incorrect air can arise. In this acceleration phase, the force of the suction air exerted on the pressure carrier supports the drawing movement of the swab roller 3 and the sliding plate 8, so that, despite the existing, relatively great adhesion of the sheet resting at the beginning of the drawing process, it can be accelerated quickly.

After the acceleration phase, which takes about a quarter of the time for the entire drawing process Can claim, the vacuum is switched off again after overflow of the recess 41, 42 and the swab roller 3 and the sliding plate 8 pull the sheet to be aligned against the stop 28 with reduced tensile force eliminated. The suction air support during the acceleration phase makes it possible to reduce the presettable pressure of the swab roller 3 against the sliding plate 8, so that a sliding movement can be made in the last phase of the drawing process. This in turn prevents the arc from forming waves after reaching the stop 28.

With the help of the clock disk 38, the suction air can thus support the drawing movement at a specific time and for a specific duration. The intensity with which the suction air acts on the sheet to be aligned can be set by the pressure reducing device 36.

If an individual adaptation or change in the duration of action of the suction air is desired during the drawing process, electronic means can be used to detect the recess, i.e. when the first control edge occurs, the control valve 34 can be controlled by an adjustable timer. However, the same is also possible using a further clock disk 46, which in this case is to be arranged next to the clock disk 38 on the spindle 25. The dimension of the recess extending in the circumferential direction can thus be changed by relative rotation between the clock disk 38 and the clock disk 46 shown in broken lines. Thus, an individual adaptation of the beginning of the suction air supply to the suction openings 30 to the pulling movement of the swab roller 3 and the sliding plate 8 and their duration and strength is possible.

Claims (6)

1. Device for the lateral alignment of automatically fed sheets in printing machines, in particular high-speed offset machines, in which the sheet is pressed by a dabbing roller (3) or segment, pivotably arranged on a fixed pull guide housing, on to a slide plate (8) acting as a pulling shoe and moved to and fro in said housing, and can be drawn by said plate (8) towards the stop (28) of the side guide (1), characterised in that the slide plate (8) comprises suction apertures (30), via which suction air can be supplied, whose time of supply is synchronized with the pulling movement of the slide plate (8) and the pivot movement of the dabbing roller (3), and whose duration is adjustable in that the suction air can be switched on when the dabbing roller (3) lowers to a sheet to be aligned and is either switched off or the dabbing roller (3) is lifted away when the lateral acceleration of the sheet is complete and before the stop (28) has been reached.

2. Device according to claim 1, characterised in that the suction air is controllable with a control disc (38) arranged on a spindle (25) synchronized with the sheet transport.

3. Device according to claim 2, characterised in that the control disc (38) comprises at least one peripherally extending recess (41, 42) which can be scanned with an electrical or electronic element (43), and in that the suction air can be switched on and off by means of a valve (34) controllable by the element (43).

4. Device according to one of the above claims, characterised in that a further timing disc (46) comprising at least one peripherally extending recess is arranged on the spindle (25) next to the timing disc (38), by turning which (46) the recess on the timing disc (38) scannable by the element (43) can be changed.

5. Device according to claim 3 or 4, characterised in that each recess extends over an area of approx. 90°.

6. Device according to claim 3, characterised in that each recess (41,42) corresponds gradually to the required duration of the suction effect.

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