Patent Application
20090200727
The invention relates to a buckle plate device for a folding machine comprising a buckle plate and sheet stopping means for stopping a sheet running into said buckle plate in an intake direction,.
A buckle plate device of this kind is known, for example, from DE 24 27 850 A1. In the case of this buckle plate device a paper sheet is conveyed by a pair of intake rollers into the buckle plate. In the buckle plate the sheet is conveyed to a mechanical stop the position of which can be adjusted and against which the sheet hits with its leading edge, whereby it is stopped while the sheet end is conveyed further into the folding unit by the intake rollers. Hereby a loop is formed in the folding space. When this loop is big enough, it is grasped by a subsequent pair of rollers and conveyed further into the next buckle plate or conveyed out of the folding unit through sheet guide elements. This solution is the presently prevailing one realized worldwide in folding machines which exclusively or in part fold according to the principle of buckle folding.
Due to ever increasing sheet formats and switching to automated machines, which have, for example, a motor-driven sheet stop adjustment, the buckle plates are becoming very big and heavy. Since they often have to be taken out of the machine wholly or in part for a change of task, they are very difficult to handle. Moreover, due the fact that the sheet transport speeds at the time when the leading edge of a sheet hits against a stop increase more and more, damage or marking of the leading edge of the sheet is increasingly caused. In order to avoid this, sensitive sheets must be processed more slowly. Stop rails which up to now in most cases have been divided are increasingly replaced by continuous stop rails which are costly to produce. The higher the sheet transport speed is, the stronger are the noise pulses produced when the leading edge of a sheet hits against the stop. In order to satisfy noise regulations, therefore elaborate noise protection casings are required to an increasing extent.
Through the mechanical stop the sheets have up to now always been folded with respect to the sheet edge and not with respect to the print image. Variations in the sheet dimensions thus unavoidably lead to variations in the position of the print image on the folded pages.
In order to avoid that the sheets hit against the sheet stop at a high speed, it is known, for example, from EP 0 844 205 A1 to retard the circumferential speed of the intake rollers before the leading edge of a sheet hits against the sheet stop. However, this requires a high level of control and adjustment. In the case of this technology, too, large and unhandy buckle plates have to be used for large sheet formats.
From DE 201 03 900 U1 a buckle plate device is known which, for humidification of extremely dry paper sheets, has a paper moistening means in front of the buckle plate intake, which paper moistening means is moved across the sheet. In order to be able to guarantee sufficient moistening of the paper sheet during the downwardly directed working movement of the paper moistening means, a contact pressure against the end portion of the paper sheet is generated by slightly decelerating the end of the paper sheet having run into the buckle plate by means of a braking means when running out of the buckle plate after having hit against the sheet stop.
The object underlying the invention is to provide a buckle plate device which requires little space and makes it possible to fold sheets with comparably low noise development without a mechanical stop in a sheet-edge controlled manner or in a print-image controlled manner at a high sheet transport speed.
This object is attained by a buckle plate device for a folding machine comprising a buckle plate and sheet stopping means for stopping a sheet running into said buckle plate in an intake direction, said sheet stopping means being formed by clamping means clamping an incoming sheet in order to stop it.
The design of the buckle plate device according to the invention makes it possible to build buckle plates that are considerably simpler and shorter, since in contrast to the prior art there is no mechanical stop and the clamping means can be positioned in the lower area of the buckle plate. This makes it possible to build more light-weight buckle plates which are easier to handle and require relatively little material, which is less cost-intensive, too. There are no more noise pulses of the sheet hitting against a solid stop rail, the intensity of which has been increasing with a rising machine speed in the prior art. They are replaced by more quiet noise pulses, which do furthermore not increase with the machine speed, of the clamping means with clamping elements acting transversely to the sheet transport direction. Therefore noise protection hoods which require a lot of space and material and are cost-intensive, as necessary in the prior art, can be simplified.
Due to the fact that the sheets do not hit against a stop with their leading edge, there is no damage or marking of the leading edge of the sheets. Therefore it is also possible to process sensitive papers at a higher speed. Likewise there is thus no wave formation in the sheets, which is disadvantageous to the folding quality, and no necessity for a small buckle plate width in the area of the buckle plate behind the clamping means in order to avoid or minimize this wave formation, as well as there is thus no limitation of the processing speed, especially in the case of sheets which are not rigid.
In an advantageous embodiment of the buckle plate device according to the invention the clamping means has, at both sides of the sheet plane of an incoming sheet, first and second clamping elements arranged opposite one another. The first clamping elements are preferably moveable in the direction of the corresponding second clamping elements by a drive from an initial position into a clamping position in order to clamp an incoming sheet. Pairs of first and second clamping elements are preferably spaced apart from one another transversely to the intake direction, wherein it is appropriate to connect the first clamping elements and the second clamping elements, respectively, by a rail in a comb-like manner and to solely drive the first clamping elements jointly by a drive. In this case only a single drive is required for the clamping means.
For a time control of the clamping means at least one sensor may be arranged in or in front of the buckle plate which emits a signal to activate the drive of at least the first clamping elements into the clamping position when an edge or a selected spot, for example, of the print image of an incoming sheet is detected. This makes it possible to electronically activate the folding process either in a controlled manner with respect to sheet edges or with respect to the print image of a sheet or with respect to markings additionally applied to a sheet. Since there is always a fixed time difference of some milliseconds between a sensor signal and the stopping of a sheet, which time difference is constant independently of the sheet transport speed, the sheet intake length from a sensor signal to the stopping of a sheet is displaced with increasing speed. This can be compensated by a selectable hold-back time of the sensor signal. Different folding lenghts can preferably be realized either by different sensor positions, or by no or equal signal delays, or by fixed sensor positions and different signal delays.
It is advantageous to support the clamping elements in a pivotable manner about a pivot axle extending in parallel to the sheet plane and perpendicularly to the intake direction such that they can be pivoted in the outlet direction of the sheet from their clamping position into a release position against the force of a bias means. This is appropriate since thereby the release of the clamping is not time-controlled, but is, just as the stopping of the sheet, controlled by the movement of the sheet. The sheet grasped by the subsequent rollers must be released from the clamping immediately at the onset of the tractive forces of the subsequent rollers in order not to be torn. Not till then the drive moves the first clamping elements back into their initial position, since the drive is given the signal for the back movement not before the sheet is drawn away.
In order to enable a sheet to run in and pass through without being obstructed, the first and second clamping elements are provided with a chamfer at their edge facing the intake opening such that an intake funnel is formed.
The width of the clamping means is preferably more than 60% of the width of the maximum paper format which can be processed in the corresponding buckle plate device. The drive can be arranged at a side of the clamping means or in an intermediate area of the clamping means. The clamping means can be divided up into several portions covering the maximum format width. A folding unit usually has four to six buckle plates, wherein in 90% of the applications only the first and the second buckle plate is actually used as a buckle plate. The other buckle plates are closed by means of sheet shunts, which pass on the sheet. The buckle plate device according to the invention can thus in most cases be used advantageously for the first and second buckle plate. It can however also be attached to each buckle plate. A buckle folding machine usually consists of one to four folding units, wherein the size and the weight of the buckle plates, the sheet speed, the intensity of the folding impetus and the size of required noise protection hoods decrease from the first to the fourth folding unit. For this reason it is appropriate to equip at least the first folding unit, but also the second folding unit with the buckle plate device according to the invention.
An exemplary embodiment of the invention is described hereinafter by means of drawings, wherein
The buckle plate device, such as the buckle plate device known from DE 24 27 850 A1, comprises a buckle plate 10 having several upper buckle plate bars 12 spaced apart from one another in parallel and several lower buckle plate bars 14 spaced apart from one another in parallel below the respective buckle plate bars 12, wherein in the figures due to the cross-sectional representation only one buckle plate bar 12, 14 can be seen. The upper buckle plate bars 12 are spaced apart from the lower buckle plate bars 14, whereby a buckle plate space 16 is formed. At the end on the intake side of the buckle plate bars 12, 14 an intake means 18 is provided which has an upper guide plate 22 and a lower guide plate 20, which are spaced apart from one another in order to form an intake opening aligned to the buckle plate space 16. Through the intake opening 18 a sheet 24 conveyed by intake rollers (not shown) is conveyed in a sheet plane BE into the buckle plate space 16.
Furthermore, at the buckle plate 10 a clamping means 26 is provided which has several upper clamping elements 28, each engaging between two neighbouring upper buckle plate bars 12, and several lower clamping elements 30, each engaging between neighbouring lower buckle plate bars 14, wherein again due to the cross-sectional representation only one clamping element 28 and 30, respectively, is shown. The upper clamping elements 28 as well as the lower clamping elements 30, respectively, are connected in a comb-like manner through a rail (not shown) extending outside the buckle plate bars 12 and 14, respectively.
The clamping elements 30 can be pivoted about a pivot axle 50 fixed on a mount and located outside the buckle plate bars 14 and extend with their free end into the buckle plate space 16. The clamping elements 28 are supported in a pivotable manner about a pivot axle 34 located outside the buckle plate bars 12, wherein the pivot axle 34 is guided such that it can be displaced in a guide 32 approximately at right angles to the sheet plane BE. The clamping elements 28, too, extend with their free end into the buckle plate space 16, wherein the free ends of the clamping elements 28 and 30 are spaced apart from one another when the clamping element 28 is in its initial position shown in
As can be seen in
The invention is not to be considered as limited to the represented embodiment. A stepper motor with one-sided or two-sided axle can be used as a drive. Instead of the stepper motor with an arm shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 102008007965.0 | Feb 2008 | DE | national |
