Automatic sheet arrival control at the leading edge

Abstract

Device for scanning the leading edges of a sheet (B) to be aligned in a sheet feeder of a sheet processing machine, with sensors (3) arranged in a feeder table (2) and assigned to leading marks (1), characterized in that the sensors (3) have several integrated measuring segments (3A, 3B, 3C) arranged one behind the other in the sheet feeder direction (T), which independently detect an overlap of an incoming sheet (B).

Description

[0001] The invention relates to a device according to the preamble of patent claim 1.

[0002] In the field of sheet feeders in sheet-processing machines, devices for detecting the position of the leading edges of sheets to be aligned are known. For this purpose, optical or other non-contact sensors are assigned to so-called leading marks, which serve to align the sheets along their leading edge.

[0003] DE 196 43 600 C2 discloses a device for influencing overlapped sheets conveyed to a printing press. In this device, the sheets are transported by conveyor belts to the area of ​​the front and side lays. A blowing device is provided above the sheet to be aligned, which directly impacts the sheet to be aligned in the overlap area with the first subsequent sheet with blowing air directed against the sheet conveying direction. This device is designed to be controlled by sensors that detect the position of the leading edge of the sheet to be aligned relative to the front lays via an evaluation and control unit.

[0004] DE 10 2005 019 617 A1 discloses a sheet-processing device, in particular a sheet-fed printing press, with a feeder designed in particular as a feed table. On the feeder, sheets, in particular printed sheets, can be moved individually or in an shingled sheet position as an shingled stream toward a sheet feeder. The feeder has alignment and / or guide elements for the sheets designed as cover marks and / or front marks and / or side marks. Furthermore, at least one capacitive sensor for capacitively scanning the sheets is assigned to the feeder.

[0005] DE 31 51 380 A1 relates to a mechanism for sensing the position of sheets, in particular for sensing, feeding and inserting sheets in printing machines with a stream feeder which is provided with front feed marks, a transport track and at least three sheet position sensors.

[0006] DE 100 36 513 A1 discloses a device for optical sheet control based on the transmission principle. The transmission sensor consists of a first fiber optic cable section arranged within contact marks, which is optically coupled to a frame-mounted light source in a contactless manner, and a frame-mounted light receiver arranged below the sheet guide path.

[0007] DE 100 28 070 A1 relates to a device for format-dependent position detection of the sheet leading edge in the feeder of sheet-processing machines. Using a minimal number of sensors, a device is created for format-controlled control of the sheet leading edge at the feed line. This device also detects the side edge area of ​​the sheet for each sheet format in order to be able to detect not only skewed or missing sheets but also unbent or otherwise retained sheet corners for each sheet format to be printed. Two inner, fixed optical sensors and at least two outer, laterally movable optical sensors are positioned in the side channel area of ​​the respective sheet format to be printed.

[0008] DE 102 46 482 A1 discloses a measuring device and a method for determining the speed of a moving object. Transient markings are continuously applied to the object by multiplying the number of detected markings compared to the number of markings resulting from a marking generation initiated by the detection of a marking after it has passed through a measuring section. Both multiplying the number of markings by multiplying the repetition frequency of marking pulses and multiplying the number of measuring points along the measuring section ensure a clear speed measurement.

[0009] DE 29 13 410 C2 relates to a photoelectric measuring device for the valuable detection of the position of an edge of a sheet relative to a reference line on a surface of a sheet-fed rotary printing press. In the area near the reference line, several photoelectric evaluation units are located opposite a light source. Each photoelectric evaluation unit converts a light signal into a corresponding electrical signal, which is fed to a counting circuit. An optical fiber with a maximum thickness of 0.01 mm is arranged between the light source and each photoelectric evaluation unit, and the optical fibers are arranged one behind the other in at least one row, close together, relative to the sheet edge to be measured. The optical fiber ends facing the sheet and the light source have a flat end face.

[0010] Furthermore, a leading edge sensor is known from DE 10 2004 040 620 A1. This sensor device is arranged below front lays with sensors. The front lays are arranged in the feeder device for aligning the sheets at their leading edge. The sensors are longitudinally movable in a guide. The sensors can be positioned relative to the front lays using adjusting means. The sensors scan the sheet edge at a position in the direction of sheet transport toward the front lays.

[0011] The object of the invention is to achieve improved measuring accuracy in a device according to the preamble of patent claim 1.

[0012] The solution to this problem is based on the features of patent claim 1.

[0013] The advantages of the invention are that the sheet edge can be recorded in detail, thus making it possible to make a statement about the functional accuracy of the sheet system more quickly and accurately.

[0014] For this purpose, several light sensors are arranged one behind the other in the direction of sheet travel. This enables automatic sheet arrival control at the leading edge. The use of a sensor with three integrated segments, which independently detect overlap of the incoming sheet, improves measurement accuracy.

[0015] The measuring principle is the reference surface sensor, in which a correspondingly polished underside of the cover mark forms the reflection surface. Sensor evaluation is based on a two-channel observation, with triangulation and intensity measurements being performed.

[0016] This results in various advantages: 1. The measurement is independent of the printing material. 2. No manual adjustment is necessary. 3. A reliable detection is carried out compared to the known solutions, since a reference value is available. 4. Contamination and fault indications are possible. 5. Skew adjustment and detection is possible.

[0017] In the following, an embodiment example is described using drawings.

[0018] Show Fig. 1 a state-of-the-art light sensor and Fig. 2 a light sensor according to the invention.

[0019] In Fig. 1 shows a light sensor of a known type. Such light sensors are arranged in the feed area of ​​a sheet processing machine. There, a row of front lays 1 is assigned to the downstream end of a feed table 2 in the transport direction T. A sheet B is fed against the front lays 1 for alignment. The presence of sheet B or the detection of the position of its leading edge is possible by means of sensors 3 arranged below the front lays 1 in the feed table 2. The sensor 3 can be a light sensor. If no sheet B is present, the sensor 2 sees nothing, since the front lay 1 has an opening 6 in this area. Furthermore, the sensor 2 can detect the offset arrival of the leading edge of sheet B at the front lay 2.

[0020] For different operating conditions, the sensor 3 can be displaced relative to the front lay 2 in the transport direction T. For this purpose, it is arranged in a guide 7 and has an adjustment spindle 4 for its adjustment. The end position is limited by a stop 5. The guide 7 of the sensor 3 is also connected to the holder of the front lays 1. When the front lays 1 are adjusted, the sensor 3 is also displaced.

[0021] In a further configuration, the light sensor guide 7 is decoupled from an individual front lay 1. The light sensor position is adjusted by means of a separate motor, controlled by a machine control program, e.g., a control station program, depending on the preselected profile of all individually motor-adjusted front lays and taking into account the respective reflectance of the printing substrate.

[0022] In Fig.2 shows the light sensor according to the invention in the installation area of ​​a sheet processing machine.

[0023] Here, a sensor 3 is designed with three integrated measuring segments 3A, 3B, 3C, which independently detect and evaluate an overlap of the incoming sheet B.

[0024] The sensor 3 is arranged in the feed table 2 upstream of the front lays 1 in the sheet transport direction T. The sensor 3 has three measuring segments 3A, 3B and 3C arranged one behind the other in the sheet transport direction T. The sensor 3 is directed with its measuring beams onto a reflection surface 9 on the underside of a cover lay 8.

[0025] The cover stamp 8 is connected here with a front stamp 1

[0026] The sensors 3 can be assigned to all or several cover marks 8 in the area of ​​a sheet feeder 2. Cover marks 8 can be arranged on all or several front marks 1.

[0027] The measuring principle is that of a reference surface probe, in which a correspondingly polished underside of the cover marks 8 is provided as reflection surfaces 9.

[0028] The signal evaluation of sensor 3 is carried out in a two-channel evaluation device which is connected to the control system of the sheet processing machine. a. A triangulation measurement is carried out, whereby a transmitter and receiver beam are arranged at an angle to each other and can thus detect or not detect an existing measuring surface. b. An intensity measurement is carried out, whereby the measuring signal is evaluated with regard to its strength so that false reflections cannot lead to an incorrect evaluation.

[0029] This offers several advantages. First, it is independent of the substrate and requires no manual adjustments. Furthermore, reliable detection is possible, as a specific measurement position can be specified as a reference value. Furthermore, evaluations with a contamination and fault indicator are possible. Finally, skew sheet adjustment and detection are easily possible. List of reference symbols 1 front stamp 2 feed tables 3 Sensor 4 adjusting spindle 5 stop 6 Opening 7 Leadership 8 cover mark 9 Reflection surface B Bow T Sheet travel direction

Claims

[1] Device for scanning the leading edges of a sheet (B) to be aligned in a sheet feeder of a sheet processing machine, with sensors (3) arranged in a feeder table (2) and associated with leading marks (1), characterized by that the sensors (3) have a plurality of integrated measuring segments (3A, 3B, 3C) arranged one behind the other in the sheet travel direction (T), which independently of one another detect an overlap of an incoming sheet (B). [2] Device according to claim 1, characterized by that integrated measuring segments (3A, 3B, 3C) of the sensors (3) arranged one behind the other in the sheet travel direction (T) generate independent measuring signals and that the measuring signals can be evaluated from one another. [3] Device according to claim 1 or 2, characterized by that the sensors (3) are assigned to a reflection surface (9) which can be covered by the sheet leading edge in the area of ​​scanning of a leading edge of the sheet (B) to be detected. [4] Device according to claims 1 to 3, characterized by that the reflection surface (9) is arranged on the underside of a cover mark (8) which covers the front edge of the sheet (B) to be detected during sheet alignment parallel to the sheet transport direction (T). [5] Device according to claims 1 to 4, characterized by that an evaluation device is provided by means of which the signals of the sensors (3) on the integrated measuring segments (3A, 3B, 3C) are recorded and evaluated and that the evaluation device is linked to a control of the sheet processing machine. [6] Device according to claim 5, characterized by that an evaluation device evaluates the signals of the sensors (3) according to the method of triangulation measurement and / or intensity measurement.

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