EP0453835B1 - Sheet-feeder for a machine manufacturing those sheets - Google Patents

Description

The invention relates to a feeder for sheets in a sheet-processing machine, in particular a sheet-fed rotary printing press, which has the generic features according to the preamble of claim 1.

Such an investor is known from DE-OS 36 09 550. In this arrangement, blowing nozzles for pre-loosening are arranged adjacently in a row and are directed at the top sheet in the sheet stack at the sheet trailing edge and are continuously supplied with blowing air from a central blowing air source. The feed to other blowing nozzles, which are different in design from the former, can be regulated in the feeder working cycle in order to form a kind of air cushion made of carrier air for the upper sheet, which is lifted off by a suction cup. The adaptation to different sheet material, in particular to different paper qualities, takes place by adjusting the height and the direction of action of the nozzles, the air flow and by appropriate selection of the nozzle shapes. Despite such measures, it happens, especially with increasing machine speeds, that the sheets in the sheet stack do not detach from one another at the rear edge and / or at the front edge and sheets are not correctly recorded by the conveying means that transport it to the feeder, or multiple sheets get into the feeder and trigger a machine stop. Heavy papers in particular, such as cardboard, tend to form waves, which affects the tightness of the sheet to be lifted on the separating suction device, but also the operational safety of the feeder function is limited when it comes to thin, stuck paper types. The top sheet, raised at the rear edge, is not blown far enough with air, so that its transport is not ensured.

For the purpose of achieving a better mounting of the sheet after lifting it from the sheet stack and an improved function of the feeder, it is known from DE-PS 1 699 507 to increase the number of separating suction devices and also an increased number of drag suction devices in several over the Arranging rows of sheet width in succession in the conveying direction of the sheet, but this results in a considerable additional effort and the air requirement, and thus also the energy requirement, increases accordingly.

The object of the invention is to achieve an increase in the operational reliability of the feeder regardless of the quality of the sheet material to be processed and an increase in the printing speed with inexpensive means and a lower energy expenditure. The invention solves this problem by training features according to the characterizing part of patent claim 1.

These training features separate blown air with an increased pressure compared to the central air from a blow air source independent of the general blow air supply to the feeder in the work cycle of the feeder to separate the trailing edge of the uppermost sheet from the sheet stack by loosening blowers advantageously into the stack, this sheet in at is known to be lifted by a suitable separating device on the rear edge. Under these raised arches, air is blown at a higher pressure from the separate blast air source in the work cycle of the machine, so that the separation of this arch from the arch underneath to the front edge of the arch takes place with significantly improved operational reliability than before. The air cushion built up in this way can be individually defined to the requirements depending on the sheet material and the machine speed and thus more optimally be designed as before. For investors who have a suction head with a probe foot that can be placed on the rear edge of the uppermost sheet in the stack of sheets and via which air is usually blown under the top sheet, air is expelled from the separate blast air source advantageously via the nozzles in this foot and others , adjacent air-jet nozzles, which can be directed obliquely to the side from the center of the bow in a known manner, or possibly only via one of these two blowing nozzles.

The supply of the air nozzles (in the feeler foot and in the air blowers) and loosening blowers with separate blown air is advantageously carried out by a relatively small compressor via a control valve, which is designed as a rotary valve and is coupled to the drive of the suction head, in particular drive elements of the feeler foot. This feature has a particular advantage because it makes synchronous operation of the rotary valve with the drive elements of the suction head, in particular the feeler foot, easier and the blowing times for the separate blowing air can be determined more precisely and possibly also be extremely short. In addition, the separate supply of the blowing nozzles for the carrier air and for the separating air can be controlled more individually, since this blowing air is independent of the conditions of the general blowing air supply. In particular, this separate blown air supply for separating and blowing under the lifted sheet enables higher pressures, with possibly reduced blowing times. The general blowing air generation does not have to generate the higher pressure, but can possibly work with a reduced pressure, which is an economic advantage.

In an advantageous embodiment of the inventive concept, some of the trailing edge blowers provided on the trailing edge in the region of the upper sheets of the sheet stack are Can also be connected to the separate blown air supply, which increases the flexibility to adapt to special operating conditions due to the higher pressure available.

By supplying the air under the upper, raised bend blowing nozzles with separate blowing air, not only is the operational safety increased, but at the same time the required air volume is reduced because shorter blowing times are possible or the general blowing air supply can work at a lower pressure, so that a lower one Energy consumption occurs, which relieves the environment.

In the drawing, the invention is shown in one embodiment.

Fig. 1

eine schematische Draufsicht auf einen Anleger mit einem Schaltschema für die Luftversorgung,

Fig. 2

eine Darstellung entsprechend Figur 1 mit einem geänderten Schaltschema für die Luftversorgung,

Fig. 3

eine Rückansicht der an der Bogenhinterkante wirksamen Blasdüsen in einem gegenüber Figur 1 und 2 vergrößerten Maßstab,

Fig. 4

einen Schnitt nach der Linie IV - IV der Figur 3 und

Fig. 5

einen Schnitt nach der Linie V - V der Figur 3.

Show it:

Fig. 1

a schematic plan view of a feeder with a circuit diagram for the air supply,

Fig. 2

2 shows a representation corresponding to FIG. 1 with a modified circuit diagram for the air supply,

Fig. 3

3 shows a rear view of the blowing nozzles effective on the trailing edge of the sheet, on an enlarged scale compared to FIGS. 1 and 2,

Fig. 4

a section along the line IV - IV of Figure 3 and

Fig. 5

a section along the line V - V of Figure 3.

Figures 1 and 2 show a plan view of the uppermost sheet 1 in the sheet stack and on the suction head 2 shown as a block diagram. On the underside of the suction head 2 is the tactile foot 3 driven in the work cycle of the feeder. The separating device, for example consisting of one or more suction cups, for lifting the uppermost sheet from the sheet stack is not shown in the drawing for the sake of a better overview. This separating device can be designed in a conventional manner.

In the area of the rear edge of the upper sheet 1 in the sheet stack, loosening blowers 4 (FIGS. 3 and 5) directed to the rear sheet edge are arranged in a row next to one another in a row on a transverse tube 5. On the tube 5, trailing edge blowers 10 offset from the center are arranged as loosening blowers for separating the uppermost sheet. To the side of the sheet stack, further diagonal blowers 6 are provided in the area of the upper sheet. The trailing edge blower 10 and the diagonal blower 6 are permanently supplied with blown air from a central air supply 8 or another blown air source in the circuit diagram according to FIG. 1 via feed lines 7. For the blowing nozzles 9 in the feeler foot 3 (FIGS. 3 and 4) as well as for two or more side-by-side air blowers 11 and loosening blowers 4, which are arranged obliquely outwards in the example, a separate blowing air supply is provided by means of a compressor 12 which is considerably less powerful than the central unit provided that is effective and controllable independently of the central air supply 8 with an increased pressure. If necessary, however, the rear edge blower 10 can also be supplied with separate blowing air. The blown air from the separate compressor 12 is fed and controlled through line 13 via a rotary valve 14, the rotary valve 14 being coupled to drive elements of the suction head, preferably to drive elements of the sensing foot 3, so that the rotary valve 14 is synchronous with the Feet movement around runs and enables exact control of the separate blowing air in the nozzles 9 and blowers 11.

If necessary, according to the circuit diagram in Fig. 2, nozzles in the trailing edge blowers 10 can be supplied with the separate blowing air from the compressor 12 or another source of separate blowing air, if this increases the operational reliability when separating and in particular when lifting the top sheet from Sheet stack is achievable.

REFERENCE SIGN LIST

1

arc

2nd

Suction head

3rd

Feet

4th

Loosening blower

5

Support tube

6

Diagonal blower

7

Supply

8th

Central air supply

9

Blow nozzle

10th

Trailing edge blower

11

Air blowers

12th

compressor

13

Supply

14

Rotary valve

Claims (4)

1. Feeder for sheets in a sheet-processing machine, in which feeder blower nozzles for preliminary loosening of the top sheets of a sheet pile are directed at least onto the trailing edge of the top sheets in the sheet pile, and blower nozzles are provided which blow carrier air from the trailing edge of the sheet under the top sheet, which has been lifted from the sheet pile by means of a separating device, in the operating cycle of the feeder, characterised in that blower nozzles (9, 11) for carrier air can be charged with compressed air from a separate compressed-air source (12), which can be controlled independently of a central compressed-air supply (8) of the feeder, by a control valve (14), driven synchronously with the separating device, in the operating cycle of the feeder.
2. Feeder according to Claim 1, having a pressure foot which is driven so as to swivel in and swivel out and is placed periodically in the operating cycle on the trailing edge of the top sheet in the sheet pile, characterised in that the drive of the control valve (14) (rotary valve) for the separate carrier air, which is fed in cycles to the blower nozzles (9, 11), is coupled to the drive for the pressure foot (3).
3. Feeder according to Claims 1 and 2, characterised in that the blower nozzles (9, 11) for carrier air are charged in surges.
4. Feeder according to the preceding claims, characterised in that further trailing edge blowers (10), which are permanently charged with compressed air, are arranged on the rear side of the sheet pile next to the loosening blowers (4) which are connected to the separate compressed-air source (12) and are charged with compressed air in the operating cycle of the machine, which trailing edge blowers can optionally likewise be connected to the separate compressed-air source (12).

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