CA2322081A1 - Method and apparatus for delivering generally flat articles to a hopper - Google Patents

Description

METHOD AND APPARUATUS FOR DELIVERING GENERALLY FLAT
ARTICLES TO A HOPPER
BACKGROUND OF THE INVENTION

The present invention relates to methods and apparatus for delivering flat products such as a printed sheet signatures ("signatures") to a hopper, where the flat products are received stacked adjacently on-edge and must be stacked oriented horizontally into the hopper. Although the present invention will be described by reference to the handling of signatures in a bindery process, it shall be deemed applicable in a variety of applications dealing with flat products in sheet form.
More specifically, the invention aims at providing a high speed and reliable method and apparatus for loading a hopper such as used in systems feeding a signature gathering saddle conveyor of a bindery line for the manufacture of books, magazine or the like. The invention is particularly intended for use with a sheet gatherer characterised by a vacuum belt conveyer bed, such as Kolbus ZU 840. In this type of apparatuses, the signatures are individually pulled from the bottom of a horizontal stack in the hopper, under the action of a vacuum belt conveyer.
Therefore, the principal object of the invention is to provide a method and an apparatus featuring a very high level of separation of the signatures coming from the folding operation, while avoiding causing any superficial distortions on the signatures or excessive load to be supported by the vacuum bed that could impair proper operation of the feed system. The feed system is then made able to feed one signature at a time to the bindery line with improved reliability.

2 Traditionally, the loading of bindery line systems, generally comprising a hopper and a rotary feeding drum, was manually accomplished by an attendant. When the signatures are coming from the folding operation, they are tightly compressed to form a bundle and some of them frequently adhere to each other depending on various printing and storage conditions. It is well known in the field that the reliability and through-output of the bindery line is mainly lying on the ability to properly operate signature separation, as traditionally executed by the attendant, so that the feeding system will continuously succeed at transferring one signature at a time to the gathering conveyer, thus avoiding costly interruptions of the bindery Line. The manual operation of separation is usually carried-out by the attendant by taking a pile of signatures and bending the pile back and forth a few times.
Additionally, some tapping of the edges of the pile on a generally horizontal flat surface may be performed. In more recent days, automatic hopper loader:> have been provided by the industry to accomplish the task of loading the holler of feeding systems, and a main challenge still resides in performing proper separation of the signatures prior to feeding.
The recent introduction of a vacuum belt bed type of signature feeding system as indicated above has brought additional constrains on hopper loaders. In order to perform in a reliable manner, the vacuum belt conveyer of the signature feeding equipment must first rely on a good contact between the signatures and the vacuum belt, so that sufficient suction force will be created to successfully pull the bottom signature from the stack of horizontally oriented signatures by overcoming the friction force.
Surface imperfections such as a folded or otherwise distorted sheet appearing at the downward face of the signature may cause poor contact with the perforated vacuum

3 belt, leading to air leakage which in turn substantially reduces the adhesion force. A miss-feed may thus be caused since adhesion of the signature to the belt could then become weaker than the opposing friction force due to the weight of the stack being supported by the bottom signature.
Secondly, it is consequently of prime importance to maintain said opposing friction force within specific operational limits in order to assure proper operation of the system feeder. Indeed, while a minimum stack height will help maintaining the bottom signature in close contact with the vacuum belt without exceeding drag capacity of the vacuum conveyor, a pile of excessive thickness will cause too much friction force to be developed on top of the bottom signature, which will overcome drag force and prevent proper feed, thus leading to miss-feed and system interruption. Similarly, suddenly dropping many signatures within a short period of time into the hopper will generate an impact force with equivalent effects.
Some currently available signature loaders perform delivering of signatures, from tightly stacked adjacently on-edge in incoming bundles (usually standing on the backbone), converted to a shingle stream as needed to properly feed a feeder hopper with horizontally oriented signatures. For instance, the apparatus described in US
patent 4,747,592, granted to Pessina in 1988 can be used to feed a Kolbus ZU 840 vacuum belt signature feeder. However, this early concept yields frequent miss-feed occurrences due to poor control of stack's height into the hopper and signature handling throughout the conveying path that promote separation without preserving the integrity of signature top sheets. Indeed, signatures are delivered into the hopper by batches through start and stop cycles of the output conveyer, which generates rapid changes in the load

4 supported by the vacuum belt conveyer. Moreover, signatures are processed through a three conveyer path without overlapping sections, which causes erratic behaviour of the signatures at interfaces potentially leading to damages to top pages, which in turn causes vacuum leakage at the feeder's belt conveyer and risks of miss-feed.
Our analysis and experiences indicate that in creating a forwardly inclined shingled stream of signatures from a bundle of vertically stacked signatures, signatures at the interface of adjacent conveyers, are successively subject to pressure from upstream signatures and rapid acceleration into a void created by the acceleration of the downstream signatures. The resulting erratic behaviour of the signature may cause it to split open at its top edge-since signatures are standing on their backbone- with the possibility of having top sheets to bend outwardly and eventually be folded or otherwise distorted when falling against downstream signatures. When feeding a vacuum belt feeder, such distortions and damages may cause malfunction as explained above. Therefor, it has been found that to avoid such a problem in that type of application, signatures must be smoothly accelerated and separated to form the shingle stream through many successive conveyors having overlapping sections at their interfaces, gradually increasing conveying speeds and gradually increasing upward inclination.
There are very few feeder concepts implementing a comparable approach and, still, in different applications or with important limitations. Besides the Pessina concept described above ('592), US patent 5,238,239 delivered to LaChapelle in 1993, shows a carton blank prefeeding apparatus featuring a single conveyer with an horizontal section followed by a slightly inclined section and a third section with a continuously variable inclination. However, ' CA 02322081 2000-09-22 that apparatus implements constant conveying speed throughout the path and does not perform sheet separation based on changes of linear speed of successive conveyer sections.
In Us patent 3,674,258 granted to Maier, 3r. in 1972, the disclosed apparatus converts stacks of horizontally oriented sheet material to a shingle stream. The stacks are loaded on a section of intermittently operating horizontal in-feed conveyer, are transferred to a second continuously running horizontal conveyer and the bottommost sheets are then pull out one after the other when reaching a steeply upwardly inclined conveyer section running at a higher linear speed and terminated by a horizontal output section.
The apparatus thus relies on up to four conveyers to perform transport, separation and conversion of signatures to a shingle stream. However, as indicated above, such an apparatus would create problematic damages to top sheets of signatures fed standing on their backbone, because of the sharp change in slope and speed at the interface of the second and third conveyers.
The apparatus disclosed in US patent 4,783,065, issued to Graves in 1988, is also designed to convert stacks of horizontally oriented sheet material sections to a shingle stream, but advantageously implements a gradually increasing slope along the feed path. Nevertheless, the structure does not offer provision .for gradual increase in the speed from one conveyer section to the downstream one.
The above review of the prior art clearly shows that no reasonably reliable and practical solution exist to solve the problem of automatically handling a bundle of vertically oriented signatures standing on their backbone to deliver signatures to a hopper in shingle stream form, while:

a) providing a high level of separation, b)preserving the physical integrity of the bottommost sheets of each signature, and c) providing precise control of the stack height into the hopper.
SUMMARY OF THE INVENTION
The present invention overcomes the limitations and drawbacks of the above mentioned inventions of the prior art, and more specifically:
it is a first object of the instant invention to provide a method and an apparatus carrying-out the method for delivering flat objects such as signatures to a hopper receiving the objects for one at a time feeding, in which separation of the products potentially adhering to each other is accomplished with a high level of reliability:
it is another object of the present invention to provide a simple and very reliable method and an apparatus carrying-out the method for delivering flat objects such as signatures to a hopper while preventing damages made to top sheets of the signatures during conversion of stacks of signatures standing on their backbone to a shingle stream;
it is another object of the present invention to provide a method and an apparatus carrying-out the method for delivering flat objects such as s5_gnatures to a hopper, providing multiple gradual increases in speed and vertical orientation through successive and partially overlapping conveyer sections;
it is a further object of the present invention to provide a method and an apparatus carrying-out the method for delivering flat products into a hopper at a substantially constant pace and maintaining a substantially constant predetermined level of signatures in said hopper;
it is a further object of the present invention to provide a method and an apparatus carrying-out the method for delivering flat products into a hopper, said method and apparatus providing such a smooth operation and high level of control to comply with the operating requirements of a very wide range of signature feeding equipment, and more particularly with vacuum belt type of signature feeding equipment.
it is a further object of the present invention to provide a method and an apparatus carrying-out the method for delivering flat objects such as signatures to a hopper, said method and apparatus satisfying high speed operation to 20 000 items per hour;
These objects and other objects and features of the present invention will become apparent through the following description that will be carried out by reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevation view of the preferred embodiment of the apparatus of the present invention, feeding the hopper of a signature feeding equipment.
FIG.2 is a plane view of the apparatus of the present invention, showing the relationship between the four conveyer sections.

' CA 02322081 2000-09-22 DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the method and flat product delivering apparatus of the present invention will now be described in detail referring to the appended drawings.
Referring to FIG. l, there is provided an apparatus generally identified by numeral 1, which is designed to deliver incoming bundled signatures 2 standing upright on their backbone to a hopper 40 of the feeding system 100 of a bindery line as a horizontally oriented stack 41.
The preferred delivering method for performing high reliability separation basically resides in:
a) placing and transporting the signatures on an in-feed conveyor, standing substantially upright on their backbone;
b) transferring the signatures to a second partially overlapping conveyor running at a slightly higher speed and substantially identical slope with respect to the in-feed conveyor, so that signatures are accelerated to slightly space apart from the upstream signatures and adopt a looser span due to released pressure;
c) transferring the signatures to a third partially overlapping conveyor running at a slightly higher speed and slightly upwardly inclined with respect to the second conveyer to form a slightly forwardly inclined stream of signatures d) transferring the signatures to a fourth partially overlapping conveyor running at a substantially higher speed and adopting a substantially steeper upward slope with respect to the third one, to further separate the signatures at their lower edge and form a further inclined shingle stream:
e) transporting and delivering the signature shingled ' CA 02322081 2000-09-22 stream at a substantially steady pace depending on the processing pace of the downstream feeding system, to fill a feeding system hopper with a stack of horizontally oriented signatures of substantially constant predetermined height, said signatures having their backbone oriented upstream.
Preferably, in using this method, the in-feed conveyer and the first conveyer are set substantially horizontal, the first conveyer having a linear speed about 15% higher than the in-feed conveyer. The second conveyer is sloped to about 15 degrees and set to a linear speed from 10 to 15% higher than the second conveyer. These three conveyers are synchronised together so that the speed ratios are maintained throughout the entire speed range.
The fourth conveyer is sloped to about 30 to 40 degrees and its speed is about twice the speed of the third conveyer, but is automatically set according to the processing pace of a downstream piece of equipment, the level of signatures in the hopper and a thickness parameter of a handled signature.
The preferred method principally relies on a plurality of mainly axial expansion cycles to promote signature separation, rather than inducing mainly shear stress components which would be more likely to create damages on top sheets of the signatures. The very smooth processing of the signatures prevents the loose sheet edges at the upper end of a signature to bend forwardly sufficiently to be subject to folding or similar damages by a compression force from the upstream signatures. That feature along with the accurate closed loop control of the stack height in the hopper significantly contributes to increase the yield of the feeding system.

Fig.1 and 2 show the preferred apparatus to carry-out the aforementioned method. The apparatus generally identified by numeral 1 is supported on a mobile frame 50. A bundle of signatures 2 is placed on the upstream portion of a substantially horizontal in-feed conveyor 3 and the straps and end plates of the downstream bundle are removed to release the signatures, retained between the new bundle and the downstream signatures. The free signatures are conveyed on in-feed conveyor 3 preferably made of four steel flat chains such as 7, up to a partially overlapping horizontal first belt conveyor 4 made of four medium friction belts such as 8. The downstream end of belt conveyer 4 is in turn feeding a second partially overlapping relatively short belt conveyer 5 made of four medium friction belts such as 9, and slightly inclined upwardly with an angle of about 15 degrees. These three upstream conveyers 3, 4, 5 are driven by a common variable speed motor il through as a speed reducer 12, a clutch 13 and a series of axles and sprockets connected by chains in a manner well known to one with ordinary skills in the art, so to provide respective conveyer linear speeds smoothly increasing in the downstream direction with approximate ratios of 1:1.15:1.3.
The downstream end of conveyer 5 discharges on a third belt conveyer 6 provided with three high friction surface belts such as 10 and comprising a upwardly inclined upstream portion 18 and a substantially horizontal delivery portion 19. The preferred slope of portion I8 is about 35 degrees.
Conveyer 6 is driven by its own variable speed electrical motor assembly L4 at a linear speed about two times faster than that of conveyer 5. The speed of each of the drive assemblies is responsive to the processing pace of signature feeder 100 through the control of a programmable controller (not shown) connected to a pair of level detectors L5,16, a speed encoder 102 connected to a rotary member 101 of signature feeder 100, and a control panel 17.

In operation, due to the overlapping conveyer sections, there is no dead point so that signatures are constantly being conveyed without being compressed by the upstream ones. Combined with the two slight accelerations at conveyers 4 and 5 and the slight slope of conveyer 5, signatures are smoothly being handled, accelerated and separated without erratic behaviour and risks of damages made to the top sheets. At conveyer 4 signatures tend to separate to form a looser stream which mainly begins to fall forward as a thick shingle when engaging the slightly inclined supporting surface of conveyer 5. The thin shingle of well separated physically intact signatures is formed by the more significant change in linear speed and angle occurring at section 18 of conveyer 6 and associated with a more positive transport resulting from the increased coefficient of friction of the belts such as 10. The thin forward shingle stream is then conveyed toward output section 19 of conveyer 6 for continuous delivery of signatures in hopper 40. It shall be noted that the sharp change of direction between section 18 and section 19 provides an additional means of signature separation.
Separating the signatures while preserving their physical integrity achieves a first goal toward increasing the reliability and throughoutput of a signature feed system using a vacuum belt conveyer. A second goal toward this objective is accomplished by precise control of the thickness of the stack of signatures 4I in hopper 40.
Indeed, both conveyer drive assemblies are continuously running to deliver signatures to the hopper 40 at a steady pace, thus avoiding the potential drawbacks of impacts. The appropriate speeds are set by the controller according to the following algorithm: An initial speed is determined by 1) information on the processing pace of the signature feeding equipment as indicated by speed encoder 102 and 2) an approximate average signature thickness inputted through control panel 17. The speed is then automatically adjusted according to the feedback from level indicators 15 and 16, respectively defining a upper and a lower limit, so that the top of stack 41 is always within these limits, set according to a predetermined acceptable height preferably in the order of 4 in. (10 cm). The apparatus 1 accommodates high signature delivery rates up to about. 20 000 signatures per hour.
Therefor, one can contemplate that the method and apparatus of the present invention avoid costly interruptions of the bindery line due to miss feed usually occurring at the vacuum belt bed conveyer signature feeder because of an excessive steady or momentary load in hopper 40, or because of distortions usually created on the top lower sheets of signatures by the mechanical processing.
Although the present invention has been described by means of preferred embodiments thereof, it is contemplated that various modifications may be made thereto without departing from the spirit and scope of the present invention.
Accordingly, it is intended that the embodiments described be considered only as illustrative of the present invention and that the scope thereof should not be limited thereto but be determined by reference to 'the claims hereinafter provided and their equivalents.

Claims