The invention relates to a holding-down arrangement for holding down a sheet in a sheet-bearing region of a sheet-processing machine, and to a sheet-aligning device which comprises such a holding-down arrangement.
DE A 1 611 362 discloses a sheet-aligning device which comprises a sheet-bearing device which is formed by corrugated resilient strips. On one side, the sheet-bearing device is bounded by an aligning rail which can be adjusted along an axis, transversely to the sheet-infeed direction, for adjustment to the sheet width. Provided on the other side of the sheet-bearing device are a bottom guide and a top guide, between which the sheet is introduced. The top guide and the bottom guide can likewise be adjusted along the axis, transversely to the sheet-infeed direction, for adaptation to the sheet width. Above the center of the sheet-bearing device, a holding-down bar is arranged just above the sheet-bearing device, this bar preventing an incoming sheet from rising up. In the case of wide sheet-bearing devices, it is necessary to have a plurality of holding-down bars spaced apart one beside the other in order to prevent the sheet from rising up over the entire width of the sheet-bearing device. The arrangement of a plurality of holding-down bars is presented, for example, in German Utility Model 84 06 391. The plurality of holding-down bars are fixed above the sheet-bearing device. If the sheet-bearing device is to be adjusted to a smaller format, the aligning rail can be displaced in the direction of the center of the sheet-bearing device, counter to the force of the resilient elements. Since the holding-down bars are located level with the aligning rail, it is necessary to remove holding-down bars which are fitted within the adjusting path. At the same time, it is also necessary to adjust the bottom rail and the top rail, for which reason it may be necessary to remove further holding-down bars. Installation or removal of holding-down bars, however, involves very high outlay.
The object of the invention is to provide, using means of straightforward design, a holding-down arrangement and a sheet-aligning device, provided with the holding-down arrangement, which make it possible for the sheet-aligning device to be adjusted to different sheet widths without it been necessary for holding-down elements to be installed or removed.
This object is achieved by a holding-down arrangement and by a sheet-aligning device as disclosed herein.
Advantageous developments of the holding-down arrangement according to the invention are also disclosed herein. Preferred embodiments of the sheet-aligning device are also disclosed herein.
Since the holding-down arrangement according to the invention holds down the sheets by the air jet of the blowing devices, it is possible for the holding-down arrangement to be arranged further above the sheet-bearing device than is the case with the known holding-down bars, which can be arranged just above the sheet-bearing device. The holding-down arrangement may be arranged at a higher level, in the adjusting region of an aligning rail, than the aligning rail, with the result that there is no chance of collision with one or more holding-down arrangements during the adjustment of the aligning rail. There is thus no longer any need for the holding-down arrangement to be installed or removed during adaptation of the sheet-bearing device to a sheet width.
The blowing devices are preferably arranged such that the air jet, during use, is inclined in the running direction of a sheet. It is thus possible to assist the movement of the sheet in the sheet-running direction.
Outside the adjusting region of the aligning rail, the previously known holding-down profiles may be arranged just above the sheet-bearing device since there is no risk of collision with the aligning rail here.
In the case of a preferred embodiment, the sheet-bearing device has, on the sides opposite the aligning rail, a sheet-bearing plate which has a plurality of blowing devices which are directed toward the underside of the sheet and are designed such that they direct onto the underside of the sheet an air jet which is inclined in the sheet-running direction. The air jet forms a kind of air cushion, which prevents static attraction of the sheet on the paper rest. Since the air jets are inclined in the sheet-running direction, this additionally assists the movement of the sheet in the sheet-running direction.
The blowing devices of the sheet-bearing plate and of the holding-down arrangements are connected to a pressure-generating device, it being possible for the quantity and the pressure of the air to be regulated for optimum adjustment.
Exemplary embodiments of the invention are explained in more detail hereinbelow with reference to drawings, in which:
The sheet-aligning device 10 which is shown in
A sheet-bearing plane is formed by the rollers 13 arranged in one plane. Above the sheet-bearing plane, three tubular holding-down bars 18 are arranged one beside the other in one plane, and extend in the longitudinal direction of the angled-roller table 12, i.e. in the sheet-running direction BL. Provided in the underside of the holding-down bars 18, in the region in which the first folding unit FW1 is arranged, are a plurality of through-passage openings 19 (
As has been mentioned above, the holding-down bars 18 are of tubular design. They have a closed interior 25 (
The second embodiment of the sheet-aligning device 30, which is shown in
Since the holding-down bars 44, 46, 48 are arranged at a higher level than the aligning rail 32, it is possible for the aligning rail 32, together with the angled belt 34, to be adjusted within the adjusting region without colliding with the holding-down bars 44, 46, 48. The air which passes out of the through-passage openings 58 forms a kind of air cushion for an incoming sheet, this air cushion preventing static attraction between the sheet and the bearing plate 56. This makes it possible for the bearing plate 56 to be of relatively wide configuration, with the result that there is no need for elements to be adjusted to the sheet width on that side of the sheet-aligning device 30 which is opposite the aligning guide 32.
Number | Date | Country | Kind |
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03010430 | May 2003 | EP | regional |
Number | Name | Date | Kind |
---|---|---|---|
3401930 | Bishop | Sep 1968 | A |
3918706 | Craft | Nov 1975 | A |
5183251 | Sardella | Feb 1993 | A |
20010015523 | Helmstadter et al. | Aug 2001 | A1 |
Number | Date | Country |
---|---|---|
468 077 | Nov 1928 | DE |
479 146 | Jul 1929 | DE |
519 519 | Feb 1931 | DE |
679 390 | Aug 1939 | DE |
2 139 423 | Mar 1972 | DE |
1 209 539 | May 2002 | EP |
Number | Date | Country | |
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20040245696 A1 | Dec 2004 | US |