Sheet feeding or delivering – Delivering – With transfer means between conveyor and receiver
Reexamination Certificate
1999-10-29
2001-02-20
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Delivering
With transfer means between conveyor and receiver
C271S183000
Reexamination Certificate
active
06189884
ABSTRACT:
FIELD OF APPLICATION AND PRIOR ART
In crosscutters, particularly large-format crosscutters for paper, relatively large-format sheets, mainly used as printed sheets, are cut from paper webs, quality-tested and deposited. Generally several webs coming from different paper rolls are supplied in superimposed manner to the crosscutter, so that individual sheet packs or groups are obtained, which are normally called clips. Following the crosscutter the clips are transformed in an overlapping station into a scale-like or tegulated sheet flow, i.e. mutually partially overlapping clips, which are finally deposited in a depositing or storage point or in a stacking station.
Although such paper reams or stacks in part have a very large number of single sheets (approximately 10,000 to 15,000), with the high operating speed of such crosscutters a pallet would be full with such a stack after only a few minutes. As it is impossible to entirely shutdown the machine for stack change purposes, hitherto, as a function of the crosscutter construction by means of a connecting switch or points positioned following the crosscutter a number of clips have been removed and which according to the degree of scaling at least corresponded to the length of one sheet, in order to then operate a switch or points within the gap and control the following sheet flow portion to a second depositing point on which another stack has been collected, until the first has been conveyed away and therefore the depositing point could again be made ready to operate.
In another known crosscutter construction the gap is produced in the sheet flow by an intermediate stopping of the following sheets upstream of the feeder, which is less suitable as a result of the mechanical action on the sheets with marking-sensitive sheet material, as a result of the possible damage. In another known crosscutter construction separation of the sheet flow portion takes place in the sheet depositing station with the aid of mechanical sheet clamping devices and/or intermediate collecting devices (e.g. format-wide, insertable plate tables or collecting gratings), which has given rise to relatively high technical costs and which frequently only takes place in a completely satisfactory manner under ideal conditions due to the possible damage to sensitive sheets and the in part complicated sequence of the separating movements.
Crosscutter constructions in which the gap between the sheet flow portions is produced by the discharge of sheets or clips, are generally characterized by a relatively simple, advantageous and uncomplicated stacking process, which has the advantage of a straight, clean stack edge. However, the serious disadvantage of this construction is that the discharge of good paper sheets must take place in order to form the gap. As the discharged paper constitutes waste, this is disadvantageous both economically and ecologically. As a result of this measure alone, a crosscutter could annually produce 50 to 100 tonnes of paper waste in the form of perfect quality paper.
All attempts up to now to obviate this problem have failed, which is on the one hand due to the very high web speeds, and on the other the fact that the cut papers, particularly in the case of top quality papers, are very sensitive. Even in the case of the slightest mechanical influencing, they tend to become marked and this cannot be tolerated during further processing and in the end product.
Apparatuses for forming gaps are already known in conjunction with insensitive flat materials or products produced therefrom. Thus, DE 39 26 966 C2 discloses an apparatus for forming a gap in a staggered flow of corrugated board, in which a slowly operating feed conveyor shoves the staggered sheet flow over and beyond a gap forming position onto a more rapidly operating gap formation conveyor. As a result of the movement of the gap formation position in the conveying direction and accompanied by the simultaneous raising of the feed conveyor, a gap is produced between two corrugated board sheets. This apparatus cannot be used with the necessary operational reliability for large and sensitive paper sheets, collisions occurring in the vicinity of the gap formation position.
The same document describes an apparatus, in which there are two nested belt systems with higher and lower speeds and as a result of the different position of two guide pulleys, which are displaceable, one or other belt is brought into engagement with the paper. This apparatus has the same disadvantages as that described hereinbefore and there is the additional advantage that two different belt systems must be guided in such a way that one runs into the gap of the other.
It is also known from EP 497 002 A1 to form a gap in a staggered flow of printed products, e.g. folded sheet layers, in that use is made of parallel belts with slower and higher speeds. A central conveyor belt with a higher speed, which is positioned somewhat below the plane of the adjacent belts running at a lower speed, is brought into engagement with the layers by suction air for gap formation purposes and draws the same over the slower belts until a gap is formed. This is unacceptable for papers having sensitive surfaces, because at least on the bottom sheet it leads to markings.
PROBLEM AND SOLUTION
The problem of the invention is to provide a possibility of forming a gap in a regulated sheet flow in operationally reliable manner, also in the case of sensitive materials and for high processing speeds, without it being necessary to renounce the simple sheet feeder construction, which is of an optimum nature for the stack quality.
This problem is solved by claim
1
. Due to the fact that the last sheet of the front sheet flow portion, after which the gap is to be formed, is held on the gap formation conveyor and said end is also movable at the gap formation speed together with the gap formation conveyor, i.e. at a higher speed, and the fact that said end is at a lower level on the gap formation conveyor than the feed conveyor, a clean separation is achieved. The first sheet of the following sheet flow portion is separated by a vertical clearance from the last sheet of the front portion. It is particularly advantageous to have at the gap formation position a blowing device, which migrates with said position and then the first sheet of the following or trailing portion floats on an air cushion over the rear part of the front sheet flow portion, so that it can be advanced under the following portion.
As the holding means are preferably constituted by a controlled, operable suction device, which sucks through an air-permeable, e.g. perforated conveyor belt of the gap formation conveyor and there are also no belts running parallel to one another with different speeds and instead they only run successively, there are no relative speeds between the sheet and the belts, so that there is no need to fear any marking of sensitive sheets. The feed conveyor, which preferably runs more slowly than the conveying speed in the crosscutter area can be the one on which the staggered sheet flow is formed and directly thereafter can commence the gap formation station. Through a corresponding length compensating device the feed conveyor can be lengthened in such a way that it follows the gap formation position on initiating the gap formation process. There is a corresponding shortening of the gap formation conveyor. Normally the feed conveyor and gap formation conveyor operate at the same speed until the gap formation process is initiated.
Directly following the gap formation station can be provided a switch or points for the lossfree subdivision of the sheet flow over two conveying paths switched in the gap formed. This avoids the hitherto necessary discharge of part of the products as waste, when said subdivision is required for stack changing or other purposes. In another advantageous construction, this gap formation station, even without any subdivision into different feed quantities, can be upstream of a stack formation device, e.g. a so-called single sheet feeder
Akerman & Senterfitt
bielomatik Leuze GmbH & Co.
Bollinger David H.
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