Printing – Antismut device – Anti-offset material application
Patent
1994-07-20
1995-08-22
Burr, Edgar S.
Printing
Antismut device
Anti-offset material application
1014241, 1014161, 101417, B41L 2322, B41L 2320
Patent
active
054430054
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a device for dusting flat products, especially printed products, with a powder.
A dusting device of known kind is described in DE-PS 22 07 983. In the case of that device, an upstream and downstream air curtain ensures that no powder dust leaves the actual treatment chamber. Removal of the air in the interior by suction ensures that the air curtains divide cleanly and without turbulence at their free end adjacent to the product transport plane and that excess powder is continuously drawn off from the treatment chamber. Such dusting devices have proved successful in practice.
In modern printing machines, distinctly increased transport speeds are used and, in order to ensure that the printed products are nevertheless dusted sufficiently well that they also continue not to stick together, it is per se necessary to have a powder box that has been enlarged in the direction of transport.
SUMMARY OF THE INVENTION
It has been realized that a powder box having only small dimensions will suffice, despite the increased transport speeds, if, on the one hand, the powder density in the powder/air mixture is increased whilst at the same time, however, by improving the dynamic sealing of the powder box and improving the flow relationships in the powder box itself, undue soiling of the surroundings, as would otherwise result from increasing the powder density, is counteracted.
This becomes possible according to the invention by means of a dusting device having the features specified in claim 1.
A powder box comprising two box portions having cover walls at different distances from the product transport plane can be obtained with little expenditure.
Advantageous developments of the invention are indicated in the subclaims.
As a result of the development of the invention according to claim 2, despite the increased powder density in the interior of the powder box, no undesirable powder deposit layers are obtained on the ceiling of the downstream box portion. Such layers could fall off in an uncontrolled manner and render high-quality printed products unusable.
When the products to be dusted are transported at very high speeds, they transmit impulses to the powder/air mixture in the powder box. By means of the development of the invention according to claim 3 it is possible to compensate for that entraining effect. Even better sealing of the downstream end of the powder box is achieved in that manner.
According to DE-PS 22 07 983, described earlier, the downstream suction nozzle arrangement is situated in front of the downstream air nozzle arrangement, viewed in the direction of transport. That side-by-side arrangement results in very sharp deflection of the air in a small area. The development according to claim 5 provides for the downstream suction nozzle arrangement to be situated in the end wall of the box above the downstream air nozzle arrangement, thereby producing a less sharply bent circulation which covers a larger area of the end of the box, that is to say more a roller of air rotating counter to the transport direction than a curtain of air meeting the transport surface at right angles. That applies particularly when the downstream air nozzle arrangement is inclined.
Other developments of the invention according to claims 6 to 8 serve to improve the lateral sealing of the dusting device.
If a printed product flutters or undulates as it is moved through the dusting device, that has an adverse effect on the flow relationships in the interior of the dusting device and on the dynamic sealing of the powder box. The development of the invention according to claim 9 ensures that the products to be dusted are aligned very precisely with their intended transport surface. The printed products, which are consequently mechanically smooth as far as the powder/air mixture is concerned, can therefore take, at most, only very small amounts of unbound powder out of the powder box in addition to the powder adhering to the still wet printing inks.
The development of the invention ac
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patent: 3053180 (1962-09-01), Doyle
patent: 3333570 (1967-08-01), Paasche
patent: 4024815 (1977-05-01), Platsch
patent: 4332198 (1982-06-01), Schmoeger
patent: 4867063 (1989-09-01), Baker et al.
patent: 4882992 (1989-11-01), Schmoeger
Burr Edgar S.
Henderickson Lynn D.
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