Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR CONVEYING
GENERALLY FLAT ARTICLES
BACKGROUND OF THE INVENTION
1. Field of the invention:
The present invention relates to a method and apparatus
for delivering flat articles, in particular but not exclusively printed sheet
signatures hereinafter referred to as "signatures".
2. Brief description of the prior art:
Traditionally, loading of bindery line systems, generally
comprising a hopper and a rotary feeding drum, is manually accomplished
by an attendant. When the signatures are coming from a 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 art 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
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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. More recently,
automatic hopper loaders have been provided by the industry to
accomplish the task of loading feeding systems, but the main challenge still
resides in performing proper separation of the signatures prior to feeding.
While in some situations currently available loaders
provide an appropriate level of separation of the incoming tightly stacked
on-edge signatures from bundles, there are still many instances where the
conditions of the incoming signatures exceed the capacity of the automatic
loader to operate proper separation. These conditions relate to the
properties of the paper web used to produce the signatures, the thickness
of the signatures, the type of ink and the density and intensity of the
printed
indicia. Indeed, when heavy gauge paper with a good absorption rate is
bearing light printed text and is folded to form thick signatures, sticking of
folded and stacked signatures together is not likely to happen, and
automatic loading can be reliably and effectively accomplished with
currently available equipment. However, most of the high volume and high
speed bindery productions of the present days involve large and thin
signatures obtained from light weight glossy paper web printed with
colourful heavy indicia. Such conditions are found in the production of
magazines, catalogues, and the like and are generally faced on the stitch
bindery lines.
In spite of numerous attempts to produce signature
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bundle loaders providing an appropriate level of separation of the tightly
stacked incoming signatures, no currently available equipment can load a
stitch bindery line feeding system with a sufficient level of reliability,
given
the adverse conditions generally encountered during this operation.
Actually, most bundle loaders pay little attention to
separation and merely rely on passing the signatures from a first conveyor
to a second conveyor sloped upwardly with respect to the first one and
driven at a higher speed, thereby making the incoming on-edge signatures
to space apart at their upper end and gradually adopt the form of an
imbricated or shingled stream. Air jets or physical members are sometimes
disposed over the upper edge of the signatures to penetrate between the
signatures approaching the second conveyer and force them to separate
and urge their forward surface toward the surface of the second conveyor.
United States Patents 5,374,050 (1994) issued to Prime-Hall Enterprises,
5,282,613 (1994) granted to R.R. Donnelly & Sons Company and
4,973,038 (1990) owned by AM International Inc. present examples of that
technique which converts stacked on-edge signatures to a forward shingle
stream, with the side edges of the signatures being inclined forwardly and
upwardly.
This technique is not much different than the one used in
the feeding mechanisms themselves and therefore does not provide a
sufficient increase in reliability to hold down times to a reasonable level
when used under the adverse conditions generally encountered on
stitching lines. For that reason, certain manufacturers such as Harris-
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Intertype Corp. (US patent 3,881,718) introduce a transfer of the shingled
stream to a third conveyor running at a higher speed than the second one
to create an additional relative displacement of the signatures under the
shear stress, thus producing a thinner shingle and improving separation.
The Harris apparatus also has its third conveyer surface disposed slightly
lower than the one of the second conveyor which adds a vertical separating
action to the horizontal action provided by the speed change. However, it
can be demonstrated that the speed change method as well as vertical
stepping become less effective when the signature major faces become
substantially horizontal. This is simply due to the fact that the weight of
the
upstream signatures creates more friction between the layers at such
angles, which tends to oppose to the shear stress and keep the signatures
attached, while in a more vertical fashion, the weight of the top signatures
tends to make them slip downwardly when the lower ones are upwardly
accelerated. In a similar manner, a vertical stepping movement will make
more effective use of the weight of the signatures for separation when the
faces of the signatures adopt a substantially vertical orientation.
Taking into account the fact that on most stitching lines,
signatures must be delivered standing on their backbone to form a stack in
the hopper of the feeding system, the prior art apparatuses also feature
mechanisms to reverse the shingled signature stream or create a shingled
stream such that the lagging portion of a downstream signature rests on
the surface of the following (upstream) one. This is required when shingled
signatures are to be placed substantially vertically in the hopper, since the
downstream signatures must not be retained by following signatures in
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order to fall freely into the hopper. A certain number of mechanisms have
been proposed to that effect in the past, and only contribute to add more
complexity and risks of malfunction.
5 Very few examples of apparatuses performing signature
separation in a substantially vertical fashion are found in the prior art. A
typical approach is to try to replicate the pile bending operation manually
carried-out by the attendant. As shown in United States Patents 5,244,199
(1993) assigned to St-Denis Manufacturing, 4,750,728 (1988) granted to
Ferag AG and 4,183,517 (1980) issued to Harris Corporation, the generally
upwardly oriented edge standing signatures are passed trough one or more
conveyor sections having convergent wall members spaced by an average
distance shorter than the width of the signatures. This technique generally
requires side conveyors for proper traction of the signatures. This implies
more complex mechanisms, additional costs and a wider apparatus while
machine spacing is a critical factor to provide enough room for attending
and maintenance. Moreover, the number of bending cycles is limited to
one or two, with low amplitude and in only one direction, which is a poor
substitution for the manually performed operation.
As will be shown in the foregoing description of the
present invention, complex mechanisms as described above can be
avoided with increased reliability and cost reduction while also avoiding the
formation of the signatures into a thin shingle. Furthermore, significant
space savings can be achieved by maintaining signatures in a substantially
vertical fashion and avoiding transportation over long belt runs in thin
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shingle form.
The above review of the prior art clearly shows that no
reasonably reliable and practical solution to the problem of automatically
handling a bundle of signatures to load the feeding system of a stitch
binding machine or a comparable piece of equipment has been provided
until now.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an
apparatus for delivering generally flat articles one by one, comprising first
and second conveyors. The first conveyor has a top article-supporting
surface operated at a first linear speed in a forward direction, wherein, in
operation, a stack of generally flat articles lies on one side on the top
article-supporting surface longitudinally of the first conveyor. The second
second conveyor is installed in series with the first conveyor, operated at
a second linear speed higher than the first linear speed in the forward
direction, sloping upwardly in the forward direction, and including a
plurality of generally parallel, rotative longitudinal screws having
respective threads structured to engage a lower edge of the generally flat
articles.
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The present invention also relates to a method of delivering
generally flat articles one by one, comprising:
lying on one side a stack of generally flat articles on a top article-
supporting surface of a first conveyor longitudinally of the first conveyor;
driving the top article-supporting surface of the first conveyor at a
first linear speed in a forward direction;
transferring the generally flat articles of the stack from the top
article-supporting surface of the first conveyor to a second conveyor
installed in series with the first conveyor and including a plurality of
generally parallel, rotative longitudinal screws having respective threads
each defining a succession of ridges and grooves, the transfer of
generally flat articles comprising engaging lower edges of the generally
flat articles with the threads of the rotative longitudinal screws;
sloping the second conveyor upwardly in the forward direction;
operating the second conveyor at a second linear speed higher
than the first linear speed in the forward direction through rotation of the
longitudinal screws; and
jogging the generally flat articles by slipping the lower edges of the
generally flat articles on the successive ridges and grooves of the threads
of the rotative longitudinal screws.
In the above apparatus and method, the jogging movement of the
generally flat articles on the successive ridges and grooves of the threads
of the rotative longitudinal screws ensure reliable separation of the
generally flat articles.
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Still according to the present invention, there is provided a method
of controlling a conveyor system provided with a discharge end and a top
article-supporting surface mobile at a variable linear speed toward a
downstream article-processing equipment, wherein, in operation, a stack
of generally flat articles is placed on one side on the top article-supporting
surface longitudinally of the conveyor system to supply to the equipment
generally flat articles one by one from the discharge end. This control
method comprises measuring a rate of processing, by the article-
processing equipment, of the generally flat articles supplied from the
discharge end of the conveyor system, and adjusting the linear speed of
the top article-supporting surface in relation to the measured rate of
processing.
In accordance with preferred embodiments of the above control
method:
- the processing rate measurement comprises measuring a
speed of rotation of a rotative member of the downstream
article-processing equipment; and
- the conveyor system further comprises article-detecting
proximity sensors mounted at the discharge end, and the linear
speed adjustment comprises adjusting the linear speed of the
top article-supporting surface also in relation to signals from the
article-detecting proximity sensors.
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The objects, advantages and other features of the
present invention will become more apparent upon reading of the
following non restrictive description of a preferred embodiment thereof,
given by way of example only with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
Figure 1 is a side elevation view of the preferred
embodiment of the apparatus according to the present invention,
cooperating with a gatherer feeder;
Figure 2 is a top plan view of the apparatus of Figure 1
cooperating with a gatherer feeder;
Figure 3 is an enlarged top plan view of a portion of the
apparatus of Figure 1, showing the relative position of needles and
proximity sensors;
Figure 4a is a first side elevation view of one of the
longitudinal screws of a screw conveyor;
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Figure 4b is a second side elevation view of a distal end
section of the longitudinal screw of Figure 4a;
Figure 4c is a third side elevation view of a proximal end
5 section of the longitudinal screw of Figure 4a;
Figure 4d is a fourth side elevation view of a section of
the longitudinal screw of Figure 4a showing a dual thread;
10 Figure 5 is a side elevation view of the preferred
embodiment of the apparatus of the present invention, provided with an
optional one-at-a-time signature transporting/feeding attachment; and
Figure 6 is a schematic block diagram of a controller
circuit for adjusting the linear speed of feed and screw conveyors of the
apparatus of Figures 1 and 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The 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.
Although this preferred embodiment will be described with
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reference to the handling of signatures in a bindery process, it should be
kept in mind that the method and apparatus according to the present
invention can be used in a variety of other applications dealing with
generally flat articles, in particular but not exclusively in sheet form.
Referring to Figure 1, there is provided an apparatus
generally identified by numeral 1, which is designed to deliver incoming
bundled, stacked signatures 2 standing upright on their backbone (lower
edge) to a vertical hopper 40 co-operating with the feeding system of a
bindery line, preferably a stitch bindery line. As will be described in the
following description, the apparatus 1 conducts a signature delivering
method incorporating a highly reliable separation of the stacked
signatures.
The preferred delivering method with highly reliable
separation basically comprises:
a) placing and transporting the signatures on a downwardly and
forwardly sloped feed conveyor (optionally, this feed conveyor
slopes downwardly in the forward direction), standing on their
backbone with their faces substantially normal to the plane of the
conveyor;
b) transferring the signatures to an upwardly and forwardly sloped screw
conveyor running at a higher linear speed with respect to the feed
conveyor, so that the signatures are accelerated at their lower edge
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(backbone) and tend to mesh with the threads of the screws to slightly
space apart and form a generally vertically oriented pile;
c) vertically jogging the signatures through a slipping action, through
successive passages from ridges to grooves of the screws of the
screw conveyor;
d) dragging the lower edge (backbone) of the signatures on a row of
substantially vertical needles to provide a gating action which retains
the upstream signatures when the leading signature being pulled by
the feeding system of the downstream signature-processing
equipment.
Preferably, in using this method, an upwardly oriented
air flow is directed toward the backbones of the signatures at the pick-up
line of the screw conveyor to help performing separation of these
signatures.
The preferred method also contemplates variation of the
speed of the signatures while they are riding on the screw conveyor as an
ultimate means for further increasing the reliability of signature separation
for optimal yield of the feeding action. This is accomplished by varying the
pitch of the thread over the length of the screws, either in a continuous
manner or in successive cycles of acceleration/deceleration. Those
repeated cycles of acceleration/deceleration can be provided by the
screw conveyor through proper design and machining of the threads
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while maintaining a constant angular speed (RPM) drive. The result is
equivalent to successive passages of the signatures on several belt
conveyors running at different speeds. A high performance separation
means is thereby provided, adjacent signatures being forced to adopt
variable relative horizontal and vertical positions along the path, causing
sustained shear and tensile stress in the bundle, thus separation of the
signatures.
Furthermore, in the preferred embodiment the global
feed rate is automatically adjusted according to the speed of the
downstream equipment being fed by the apparatus 1, and the conveying
screws are provided with dual threads as shown in Figure 4d, for
adaptability to a wide range of signature thicknesses.
Figures 1 and 2 show a global view of the preferred
embodiment of the apparatus for carrying out the above recited method.
The apparatus, generally identified by reference numeral 1 in Figure 1, is
supported on a mobile frame 50. A bundle of signatures 2 (stack of
generally flat articles) is placed on the side on an upstream portion of a
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 the
downwardly sloped feed conveyor 3 preferably made of flat steel chains or
any other type of suitable belt means, up to a screw conveyor consisting of
four parallel screws 4a-d sloping upwardly. Conveyors 3 and 4 are driven
by a variable speed motor 5 through an electrical clutch 6, a speed reducer
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7, and a conventional chain and sprocket transmission system 77 finally
coupled to drive shafts 8 and 9. The shaft 8 drives a sprocket (not shown)
driving in turn chain conveyor 3, and shaft 9 drives four 90° gear
boxes
11 a-d connected to the lower end of the screws 4a-d. The system provides
a fixed ratio from about 1.15:1 to 1.2:1 between the linear speed of the
screw conveyor 4 and the linear speed of the chain conveyor 3. A
motorised driving system of the above type is well known to those of
ordinary skill in the art and, accordingly, will not be further described in
the
subject patent application.
The motor 5 and clutch 6 are controlled by a controller 10,
according to the information provided by proximity sensors 21 and 22
(Figure 3), a speed encoder 31 (Figure 1) and a control panel 30 (Figure
1 ).
As shown in Figure 3, the proximity sensor 22 is located
downstream the proximity sensor 21 at the same vertical level of a flat
plate 17 between the distal end of the screw conveyor 4 and the
downstream article-processing equipment 100. As a non limitative
example, the speed encoder 31 detects rotation of a rotary member such
as 102 (Figure 1) of the downstream article-processing equipment 100.
The control panel 30 is used to turn the apparatus 1 on and off and to
enter operational parameters such as the thickness of the signatures.
Automatic adjustment of the signature feed rate is
accomplished as follows: the speed encoder 31 provides the controller 10
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with the number of signatures being processed per minute. The controller
10 calculates a linear feed rate for a reference average signature thickness
and sets the speed of motor 5 accordingly while monitoring the signals from
the proximity sensors 21 and 22. Fine speed adjustments are then made
5 so that the leading signature is always comprised between the two
proximity sensors, i.e. sensor 22 sees no signature while sensor 21 sees
one all the time. After a few iterations, the appropriate speed is found and
maintained through start and stop cycles of clutch 6 (or, alternatively,
through appropriate control of a direct drive do servomotor (not shown and
10 replacing the motor 5 and clutch 6 arrangement) for smoother operation).
More specifically, the clutch 6 stops the conveyors 3 and 4 when the
signatures reach sensor 22 and starts them when sensor 21 senses no
presence. In the application represented in Figure 1, the accurate and soft
operation thereby provided ensures that no excessive pressure is applied
15 on the signatures against the wall 41 of hopper 40, which could prevent
suckers 101a-a and feeding mechanism 100 from successfully pulling the
leading signature. The suction cups 101 a-a repeatedly pick-up the lower
portion of the leading signature at a position comprised between the two
proximity sensors, representing a variation of a few millimetres.
It shall be noted that the aforementioned assembly
provides continuous transfer with no gap between conveyors 3 and 4, so
that the signatures 2 are smoothly transferred from conveyor 3 to conveyor
4. However, as indicated hereinabove, screw conveyor 4 is driven at a
linear speed considerably higher than the linear speed of the chain
conveyor 3 for a given rotation speed of the motor 5, and creates a change
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in the signature path of about 45° upwardly. The signatures 2 are
therefore
transferred from feed conveyor 3 to screw conveyor 4 by being suddenly
accelerated at their lower edge and forced to form an upward slope. These
actions provide a first means of separation of the signatures by way of axial
pulling and vertical shearing of adjacent signatures, mainly at the interface
of the two conveyors.
Also, the signatures are not positively transported by the
screw conveyor 4 due to the rising of the slope and to the high difference
in linear speed with respect to conveyor 3, such that some slipping occurs
making the signatures to travel along the path of the screw threads. The
resulting zig-zag like reciprocating vertical travel across ridges and grooves
creates numerous cycles of shearing action between adjacent signatures
all along the screw path. Experience showed that such a jogging carried
out at 10 to 20 strokes per second with a vertical amplitude of about 3
millimetres was much more effective at separating signatures than vibration
performed at higher frequency and lower amplitude. That shearing action
combined with the axial separation due to the tendency of the signatures
to align with the grooves and match the thread pitch provide a second
means of separation. It shall be pointed out that the screws preferably
comprise a dual thread as illustrated in Figure 4d, for optimal performance
with thinner as well as thicker signatures.
Furthermore, it is contemplated to vary the pitch of the
screw threads to create a definite number of axial dilatation and
compression cycles to further improve separation reliability. Consequently,
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it can be observed in operation that the top of the signature bundle
gradually matches the screw slope without irregularities when approaching
the forward end of the screw conveyor 4.
Just a word to mention that a short belt conveyor section
(not shown) may be provided to connect the distal end of the screw
conveyor to the hereinafter described pair of needles 19 and 20 (gating
system).
As shown in Figures 2 and 3, a pair of spring biased
needles 19 and 20 are located next to the pick-up line between proximity
sensors 21 and 22 and projects beyond the top surface of flat bottom plates
17 by a few millimetres to act as a soft stop on the lower edge of the
leading signature and provide a gating action. When the suction cups
101a-a pull the leading signature forwardly, the needles bend forwardly and
return to their original position under spring action, stopping the next
signatures as soon as they are cleared by the lower edge of the leading
signature. That action provides an ultimate means of separating the
signatures to ensure one-at-a-time feeding. It is indeed of primary
importance for proper operation of the bindery line that the pulled signature
separates easily from the stack in hopper 40 to be placed on the saddle
conveyor one at a time and avoid costly interruptions of the line upon miss
feed. The apparatus according to this preferred embodiment can perform
that task at high signature feed rates up to about 20 000 signatures per
hour.
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Optionally, air jets fed through series of holes 18a-d
provided in the flat plates 17 can be directed toward the lower edge of the
signatures approaching the pick-up line. Air penetrates between adjacent
signatures and builds up a pressure that in turn creates an axial separation
force thereby increasing their susceptibility to vertical slipping.
An apparatus 1 with a one-at-a-time signature
transporting/feeding attachment 200 as illustrated in Figure 5 can also be
provided. This attachment comprises a set of suction cups such as 201 like
a gatherer feeder which pulls the lower portion of the leading signature from
the hopper 40 to bring it in contact with a first static roller 202. A second
powered roller 203 then engages the signature and feeds it to a belt
conveyor 204 provided with rows of cleats such as 205 contacting the
backbone to positively transport the signature. The signatures are thereby
loaded one behind the other and transported over successive downward
and upward vertical paths to perform operations such as ink jet printing on
either face thereof. Signatures finish their travel on the top of the
apparatus
and are dropped one by one in a vertical or horizontal hopper to feed an
equipment such as a drum gatherer feeder for a stitching or binding line.
The present invention presents, amongst others, the
following advantages:
- separation of the generally flat articles potentially adhering to each
other is accomplished with a high level of reliability;
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- the method and apparatus for delivering generally flat articles
satisfy high speed operation requirements;
- the method and apparatus for delivering generally flat articles to a
hopper are simple and economical in construction while featuring a
high overall reliability;
- the method and apparatus for delivering generally flat articles have
the flexibility to comply with operating conditions related to a very
wide range of signature types while requiring minimal and easy set-
up, these conditions including paper gauge and finish, type of ink,
signature size, thickness and stiffness, and density and intensity of
the printed indicia;
- the method and apparatus for delivering generally flat articles
perform separation operations on the generally flat articles while
their faces form an angle of less than 45 degrees with respect to a
vertical plane, so that the most of their weight is supported by their
backbone which contributes to the separation process;
- the method and apparatus for delivering generally flat articles
avoid transportation of signatures in flat shingle form, thus providing
significant space savings;
- the signature feed rate is automatically adjusted to the speed of
the downstream signature-processing equipment;
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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
5 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.
