Sheet feeding or delivering – Feeding – Separator and conveyor
Patent
1992-08-07
1994-11-08
Skaggs, H. Grant
Sheet feeding or delivering
Feeding
Separator and conveyor
271110, 271116, 271117, 271122, 271125, B65H 500
Patent
active
053620372
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of delivering, one by one, flat articles of some stiffness, such as paper or plastics sheets or envelopes, from a stack in a direction of transport, using a feed roller exerting a pressure on an outer article of the stack, a conveyor roller opposite which a separation surface is arranged, and in which the conveyor roller and the separation surface form a separation area between the outer surface of the conveyor roller and the separation surface, the conveyor roller and the feed roller are rotated by driving means, the feed roller periodically exerts a frictional force on an outer article of the stack at the location of said roller, so that said article is shifted from the stack to the separation area, where the conveyor roller engages said article and carries in off in the direction of transport, and the pressure force exerted by the feed roller on said outer article is reduced at least while the conveyor roller engages said article.
Such a method is known from DE-A-33 34 522. Reducing the force with which the feed roller presses against the outer article of the stack when the conveyor roller engages that article, offers the advantage than a smaller separation force directed counter to the direction of transport, to be exerted by the separation surface, is required for separating two or more articles which are being fed into the separation area simultaneously by the feed roller.
In addition to being advantageous when a separation roller as proposed in DE-A-33 34 522 is used, reducing the force with which the feed roller presses against the outer article of the stack when the conveyor roller engages that article, is also advantageous when a gap separation system is used in a gap separation system the distance between the separation surface and the conveyor roller is adjusted in correspondence with the thickness of the articles to be separated and the separation surface is kept in a fixed position opposite the conveyor roller. It is true that the frictional force exerted by the article adjacent on the inside acts counter to the direction of transport, rather than in the direction of transport, but in adverse cases separation nevertheless proves problematic. This is caused by the fact that the frictional force which is exerted by the article adjacent on the inside is determined only by the dynamic mutual coefficient of friction of the articles, while the frictional force exerted by the article adjacent on the outside, acting in the direction of transport, is determined by the considerably greater static mutual coefficient of friction between the articles--for instance the outer article and the article in contact therewith--which travel at an equal speed. Without reduction of the pressure force of the feed roller when the conveyor roller is in engagement with an article supplied, it has appeared that when a gap separation system is used the successive delivery of the articles is very sensitive to a proper adjustment of the size of the gap relative to the thickness of the articles to be separated.
The manner of reducing the pressure force of the feed roller, as proposed in DE-A-33 34 522, however, requires a costly construction which comprises an electromagnet partly cancelling the pressure force and means for switching this electromagnet.
In U.S. Pat. No. 4,522,385 a method and an apparatus for transporting top sheets from a stack are described, in which a feed roller drive comprises a lost motion coupling, to avoid that a subsequent sheet is fed toward a separation area, before the previous sheet is transported away from said area. The feed roller exerts a constant pressure force on the stack, which is urged against the feed roller by a spring under the stack.
In DE-A-2 851 548 a method and an apparatus for transporting top sheets from a stack are described, in which the apparatus comprises a separating roller for separating outer sheets from a stack. To separate the sheets, the sheets are held back by edge pressing means and the outer sheet is urged past said edge pressing m
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de Haan Hendrik A.
van der Werff Jeichienus A.
Druzbick Carol L.
Hadewe B.V.
Skaggs H. Grant
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