The invention relates to a device for setting a spacing of a sheet from a guide during conveying through a printing technology machine. The device has a blown air apparatus which acts on the sheet and has an adjusting apparatus for blowing action of the blown air apparatus.
In a printing press, it is known to convey freshly printed sheets past a guide plate in such a manner as to be carried by air without contact. The height of a sheet above the guide plate can be set by the action of a blown air apparatus and/or vacuum apparatus on the sheet being changed. Typical adjusting elements are fans or blower pipes which are disposed along the conveying path individually or in groups. A large number of setting possibilities on the fans or blower pipes are available to an operator of the printing press. The operator observes the floating height of the sheet above the guide plate and sets the floating height to a desired value by changing the amount and/or direction of the blown air locally. The setting processes take a great deal of time and are imprecise, because the operator can only estimate the floating height subjectively due to unfavorable observation conditions.
In order to become independent of the experience of an operator, it is known to use control and regulating apparatuses which process signals from sensors for the floating height.
German Patent DE 197 30 042 C2 describes an apparatus for controlling sheet guidance in a sheet-fed printing press, in which the actual position of a sheet is determined with a sensor at a point of reference and compared with a setpoint position. Actuators of a blown air apparatus and/or vacuum apparatus which are directed onto a sheet are actuated as a function of the setpoint-actual value difference, with the result that the sheet end rests smoothly and completely on the circumferential surface of a cylinder while the sheet is being conveyed on the cylinder. During the control of the sheet guidance in the feeder of the sheet-fed printing press, a plurality of sensors can be directed at various points on the upper side of a sheet stack. Furthermore, rows of sensors can be used as contactless distance sensors parallel to the edges of a sheet stack.
German Published, Non-Prosecuted Patent Application DE 102 05 985 A1 shows a printing material guide element with an integrated distance sensor for sheets. When sheets are conveyed, a machine operator is shown the sensor measured values of a defined sensor or information about measured values of adjacent sensors. The machine operator can set an air flow field on the basis of the display.
German Published, Non-Prosecuted Patent Application DE 100 38 774 A1, corresponding to U.S. Pat. No. 6,889,609 and U.S. Patent Application Publication No. US 2002/0060407, has disclosed an apparatus for producing an air flow in a duplicating machine, in which ionic fans are used to support a trailing free end of a sheet that is held in grippers by a specifically set flow field, in such a way that during transport fluttering is reduced. The position of the free end of a sheet is determined with a detector and the local strength of a flow field is varied with a regulating device in such a way that the position of a desired setpoint position is approximated. Optical or ultrasound sensors which sense individual points or over a full area can be used to detect the sheet position.
In an apparatus for conveying sheets onto a stack according to German Published, Non-Prosecuted Patent Application DE 43 28 445 A1, corresponding to U.S. Pat. No. 5,582,400, a sensor is used which senses the fluttering movement of the sheets. Sensor signals are processed in a control or regulating apparatus to form adjusting signals for a blown air apparatus or vacuum apparatus.
The sensors and circuit configurations for evaluation of the sensor signals are expensive in terms of material and cost. In addition, a large number of sensors would reduce the reliability of the printing press.
It is accordingly an object of the invention to provide a device for setting a spacing of a sheet from a guide during conveying through a printing technology machine, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which provides a simple adjusting aid when setting the distance of a sheet from a guide and in which the adjusting aid improves optical observation conditions for a machine operator.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for setting a spacing of a sheet from a guide during conveying through a printing technology machine. The device comprises a blown air apparatus acting on the sheet. An adjusting apparatus adjusts blowing action of the blown air apparatus. A light source directs at least one optically visible light beam obliquely onto a surface of the sheet.
According to the invention, a light beam which can be seen well optically is directed onto the surface of a floating sheet as an adjusting aid. A machine operator can determine, even under unfavorable conditions, whether or not the sheet is at a desired floating height above the guide by using the position of the light spot on the sheet or using the number of light spots and/or using the color characteristics of the light spot.
Laser diodes providing light beams which are optionally parallelized with lenses can be used, in particular, as light sources. Two laser beams which intersect at a setpoint or desired height for a sheet are preferably used. If the actual height deviates from the setpoint height, two light spots of small diameter which are clearly separate from one another appear on the sheet. If the height of a sheet above a guide is determined at a plurality of locations with light beams, the three-dimensional position of a sheet can be monitored.
If two light beams of different color are used, in particular red and blue, the result at the intersection point of the light beams is a light spot in a mixed color, in particular green. The green light spot thus indicates the location of the desired height of the sheet above a guide. If the sheet is in front of the intersection point, two light spots with the colors red and blue appear on the surface of the sheet. If the sheet lies behind the intersection point, the red and blue light spots appear in the reversed order. An operator receives information from the color sequence of the light spots and their distance from one another as to whether and by how much the supporting air under the sheet has to be increased or reduced.
If two light beams with different cross sections are used, the result is different patterns depending on the distance of the sheets from the guide. For example, at the setpoint height, two angles which appear on the sheet can be in contact with one another exactly at the tips and, in the event of a deviation from the setpoint height, they can overlap or lie at a distance from one another.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for setting a spacing of a sheet from a guide during conveying through a printing technology machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Referring now to the figures of the drawings in detail and first, particularly, to
If, as is shown in
If the cases shown in
According to
If more than one light source pair are used which in each case intersect at a point of the setpoint plane 16, and if a blown air source 9, 10 is used which can be controlled on a time and region basis, the position of a sheet 1 with respect to the guide plate 5 can be controlled in a targeted manner. It is thus also possible to compensate for oblique positions of a sheet 1 with respect to the setpoint plane 16.
This application claims the priority, under 35 U.S.C. §119, of German Patent Application 10 2004 060 525.4, filed Dec. 16, 2004; the entire disclosure of the prior application is herewith incorporated by reference.
Number | Date | Country | Kind |
---|---|---|---|
10 2004 060 525.4 | Dec 2004 | DE | national |