GB2313364A

GB2313364A - Sheet feeder

Info

Publication number: GB2313364A
Application number: GB9710703A
Authority: GB
Inventors: Richard Kuester
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1996-05-24
Filing date: 1997-05-23
Publication date: 1997-11-26
Anticipated expiration: 2017-05-23
Also published as: DE19620937B4; DE19620937A1; JP2834724B2; GB9710703D0; CH691772A5; JPH1059566A; GB2313364B

Description

2313364 SHEET FEEDER This invention relates to a sheet feeder with a

suction head arranged over a sheet pile set on a lifting table to which suckers are arranged which can be movably driven between their raised starting position and their lower gripping position, with a sensor by means of which the height level of the sheet pile can be detected and with an adjustment device by means of which, in dependence upon the height level detected, the starting position of the suckers can be adjusted vertically to a given distance between sucker and sheet pile.

In a sheet delivery of this type, it is known to sense is the height level of the rear sheet pile region by means of a first sensor which sits mechanically on the rear end of the sheet pile. This sensor is rigidly connected with the suction head. The entire suction head is guided vertically movably and biased by a spring in the direction towards the sheet pile. Accordingly the suction head supports itself via the sensor on the sheet pile and should thus ensure the given distance between sucker and sheet pile.

2 On the one hand, the support of the sensor under the force of the spring and the weight of the suction head, particularly in the case of so-called "pumping" sheet material, i.e. compressible sheet material, leads to a depression of the sensor below the actual level of the sheet pile, so that the given distance between sucker and sheet pile can be substantially undershot.

Furthermore. the sensing takes place at only one position of the sheet pile. In this connection, with several suckers arranged next door to one another in the sheet feeding direction, and an uneven height level above the sheet pile surface, differing strokes of the suckers also need to be carried out before they can grasp the uppermost sheet.

This leads to the situation that separating suckers are not simultaneously closed off by the uppermost sheet, but at the later closing separating suckers, further air can flow into the suction system and negatively influence the satisfactory separating process.

With pulling suckers, there is the danger that the height of the movement stroke is uneven and accordingly the suction lifting times are different, which leads to a buckling of the sheet.

The invention seeks to produce a sheet feeder of the initially noted type which, independently of differing height levels in the various regions of the sheet pile surface, guarantees correct and trouble-free sheet processing.

This problem is solved in accordance with the invention in that several suckers each have a sensor arranged relative thereto and an adjustment device arranged relative thereto, wherein the sensors each detect the height level of the sheet pile in the region below the sucker coordinated thereto. Thereby, by means of identical distances to the sheet pile, the working conditions of each sucker are the same, which guarantees satisfactory sheet processing. This is provided, in particular, if each sucker has a sensor and an adjustment device.

An exact rapid and finely gauged adjustment is achieved if the adjusting device is an automatic adjusting device, particularly an electric or driven adjusting device.

Change of the level in the various regions of the sheet pile surface, which arise during the working away of the sheet pile, are automatically compensated if by means of sensor and adjustment device during the working operation of the sheet feeder, the starting position of the suckers are adjustable to the given distance.

For detecting the height level via the sensor, the movement stroke of the sucker between starting position and grasping position can be detected.

Another possibility consists in that by means of the sensor, the distance between the starting position of the sucker and the surface of the sheet pile is detectable.

In order to avoid a "pumping" of the sheet pile on its level sensing and accordingly false level results. the sensor can be a contactless sensing sensor, preferably an optical sensor.

A simple possibility for adjusting the sucker consists in that the sucker is arranged in each case in a sucker housing and the sucker housings are adjustable vertically by means of the adjustment devices. 5 The suckers can be, e.g. separating suckers or pulling suckers.

In order in a sheet delivery with a sucker arranged above a sheet pile set upon a lifting table, on which the suckers are arranged, which can be driven between their raised starting position and their lower grasping position movably, with a first sensor by means of which the height level of the sheet pile is detectable and with is an adjustment device by means of which the starting position of the sucker can be adjusted in dependence on the height level detected of the first sensor by vertical adjustment of the suction head to a given distance between sucker and sheet pile, with a second sensor by means of which the height level of the sheet pile in its front region is detectable, and a lifting device of the lifting table by means of which in dependence on the height level detected of the second sensor, the lifting table is adjustable to a given height level of the front side of the sheet pile, wherein the adjustment of the lifting device constitutes priority before the adjustment of the suction head to guarantee that the suction head does not via "pumping" of the sheet pile take up an incorrect distance relative to the sheet pile, and accordingly so that the suckers can no longer guarantee correct and trouble-free sheet processing, preferably the first sensor is a contactless sensing sensor.

Thereby, the base position of the suction head after the base adjustment of the front sheet region is directed by the lifting device. In this connection, the level of the front sheet pile is located at the right level for a further feeding unit such as, e.g. pull-off rollers while the position of the sensing head for the level at the rear region of the sheet pile is matched to it.

Also, the second sensor is, for avoiding an incorrect level interrogation, preferably a contactless sensing sensor.

Both sensors, the first andlor the second sensor, can be optical sensors.

If the sheet feeder has the features of one of claims 1 to 11, then both uneven height levels of the sheet pile between the front and rear region and also uneven height levels in the various regions of the suckers are compensated so that an optimal sheet processing is guaranteed.

Also the suction head can be automatically adjustable itself by means of an electric motor adjustment device to a given distance between sucker and sheet pile. so that this adjustment also occurs rapidly, exactly and with fine precision.

The invention is illustrated by way of example, with reference to the accompanying drawings, in which Figure 1 shows a side view of a sheet feeder according to the invention, and Figure 2 shows a rear view of the sheet feeder according 6 to Figure 1.

The sheet feeder illustrated in the Figures has a machine frame 1 with two carriers 3 arranged at a distance from one another and extending horizontally in the sheet feeding direction 2, which are connected with one another at their front and rear regions by transverse carriers 4.

Both in the front and also in the rear region of the machine frame 1 are arranged toothed wheels 5 of a lifting device, which is drivable by an electric motor and over which are guided carrier chains 6.

On the free downwardly hanging ends of the carrier chains is 6, a lifting table 7 is suspended on which a sheet pile 8 is set. By driving the toothed wheels 5, the lifting table 7 is liftable or lowerable.

In the front region of the machine frame 1 are mounted pull-off rollers 9 by means of which the respective uppermost sheet taken off from the sheet pile 8 can be fed further.

Arranged above the front region of the sheet pile 8 is a second sensor 10 which is a contactless sensing sensor by means of which the height level of the front region of the sheet pile 8 can be sensed. The signal generated by the sensor 10 is fed to a not illustrated control unit which on deviation of the height level at the front pile region from a given height level controls the lifting device of the lifting table 7 to raise or lower it.

Arranged above the rear region of the sheet pile 8 is a suction head 11 on a transverse carrier 4 in such a fashion that it is liftable or lowerable by means of a vertical threaded spindle 12 by means of an electric motor adjustment device 13.

Arranged on the suction head 11 is a contactless sensing first sensor 14, by means of which the distance between the rear region of the sheet pile 8 and the suction head 11 is detectable. A corresponding signal is, after the front pile region has been adjusted by means of the lifting device to the given height level, fed through a not illustrated control unit which controls the electric motor adjustment device 13 in such a fashion that the distance between suction head 11 and the rear sheet pile region is a given distance.

Carried by the suction head 11 are furthermore two suction units 15 arranged transversely to the sheet feeding direction 2 at a distance from one another. Each suction unit 15 has an electric motor adjustment device 16 fixedly connected with the suction head 11 from which a sucker housing 17 is vertically adjustable. e.g. via a threaded spindle.

Arranged in each sucker housing 17 guided vertically is a piston rod 18 which at its free end projecting from the sucker housing 17 carries a sucker 19. This is drivable by means of the piston rod 18 between a raised starting position and a lowered gripping position movably. In the gripping position, the sucker 19 reaches to come to rest on the uppermost sheet and grasps this by subjecting the sucker 19 to reduced pressure.

Arranged on each sucker housing 17 is a contactless sensing sensor 20 detecting the distance between the sucker housing 17 or the sucker 19 in its starting position and the region of the sheet pile 8 below the sucker.

From each sensor 20, the corresponding signals are fed to a not illustrated control unit, by which each adjusting device 16 is controlled in such a fashion that each sucker 19 takes up the same given distance to the region of the sheet pile 8 located under it.

Claims

1. Sheet feeder with a suction head arranged over a sheet pile set on a lifting table, on which suckers are arranged, which can be driven movably between their raised starting position and their lowered gripping position, with a sensor by which the height level of the sheet pile can be detected and with an adjustment device by which, in dependence on the height level detected, the starting position of the sucker is adjustable vertically to a given distance between sucker and sheet pile, characterised in that several suckers each have a sensor arranged thereto and an adjustment device arranged thereto, wherein the sensors in each case detect the height level of the sheet pile in the region below the sucker arranged thereto.

2. A sheet feeder according to Claim 1 wherein each sucker has a sensor and an adjustment device.

3. A sheet feeder according to Claim 2 wherein the adjustment device is an electric motor adjustment device.

4. A sheet feeder according to Claim 3 wherein the starting position of the sucker is adjustable to the given distance by means of the sensor and adjustment device during the working operation of the sheet feeder.

5. A sheet feeder according to Claim 4 wherein by means of the sensor, the movement stroke of the sucker between starting position and grasping position can be detected.

6. A sheet feeder according to any one of Claims 1 to 4 wherein by the sensor, the distance between the starting position of the sucker and the surface of the sheet pile is detectable.

7. A sheet feeder according to Claim 6 wherein the sensor is a contactless sensing sensor.

8. A sheet feeder according to Claim 7 wherein the sensor is an optical sensor.

9. A sheet feeder according to Claim 8 wherein the suckers are in each case arranged in a sucker housing and the sucker housings are vertically adjustable by the adjusting devices.

10. A sheet feeder according to Claim 9 wherein the suckers are separating suckers.

11. A sheet feeder according to any one of Claims 1 to 9 wherein the suckers are pulling suckers.

12. A sheet feeder with a suction head arranged above a sheet pile set on a lifting table, on which suckers are arranged, which are drivable movably between their raised starting position and their lowered gripping position, with a first sensor, by which the height level of the sheet pile is detectable at its rear region and with an adjusting device by which, in dependence on the height level detected of the first sensor, the starting position of the sucker is adjustable by vertical adjustment of the suction head to a given distance between sucker and sheet pile, with a second sensor by which the height level of the sheet pile at its front region is detectable and a lifting device of the lifting table by which in dependence on the height level detected by the second sensor, the lifting table is adjustable to a given height level of the front side of the sheet pile, wherein the adjustment of the lifting device takes priority to the adjustment of the suction head, and wherein the first sensor is a contactless sensing sensor.

13. A sheet feeder according to Claim 12 wherein the second sensor is a contactless sensing sensor.

14. A sheet feeder according to Claims 12 and 13 wherein the first and/or the second sensor is an optical sensor.

15. A sheet feeder according to Claims 12 and 14 and including the features of any one of Claims 1 to 11. is

16. A sheet feeder according to any one of Claims 12 to 15 wherein the suction head is adjustable by an electric motor adjusting device to a given distance between sucker and sheet pile. 20

17. A sheet feeder according to Claim 16 wherein the adjustment of the lifting device takes place via the second sensor and the adjustment device during the working operation of the sheet feeder. 25

18. A sheet feeder substantially as hereinbefore described with reference to the accompanying drawings.