Note: Descriptions are shown in the official language in which they were submitted.
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SINGLER DEVICE
The present invention relates to a singler device for flat
articles, e.g. letters, including first and second article
driving means to engage and drive said flat articles sequen
tially off a stack located in an input position and sideways
therefrom via a passage into a delivery position laterally
separated from said input position by lateral guiding means
for said flat articles, and article detector means mounted in
said delivery position for controlling said driving means~
Such a singler device is already known from
US patent 2 970 834. In this known device the first driving
means is mounted in the input position close to the guiding
means, whereas the second driving means is mounted in the
delivery position. These driving means are operated in succession
subs~quent to the detector means having detected the passage
of the trailing edge of a letter.
A drawback of this known device is that due to
the first driving means being mounted close to the guiding means
comprising a guide plate even a small misalignment with respect
to the guide plate between two consecutive letters in the
input position may give rise to an erroneous operation. Indeed,
when for instance the leading edge of two such consecutive
letters of the stack are misaligned to such an extent that the
second letter instead of the first one is positioned in front
of the first driving means the second letter and not the flrst
one will be carried away off the stack when this driving means
is operated. ,
Separate means might be provided to align the ~
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leading edges of the letters on the guide plate but this
requires additicnal equipment.
An ohject of the present invention is therefore
to provide a singler device of the above type but which does
not present this drawback, i.e. wherein the Elat articles are
separated from the stack in the correct order even when they
are misaligned to a certain extent.
The present invention is a singler device for flat
articles that achieves that cbjective. The device has an
input stage for storing a plurality of articles to be singulated
and a delivery stage for accepting articles from the input
stage and feedincJ sir,gulated articles to an output and a
movable drive belt for carrying the articles from the input
stage to the delivery stage. There is a first holding means
in the input ctage for holding an article on the moving drive
belt when the first holding means is activated and a second
holding means, spaced downstream from the first holding means
along the direction of travel of the drive belt, for holding
an article on the moving drive belt when said second holding
means is activated. First and second sensor means in the
delivery stage provide a signal upon detection of the presence
or absence of an article on the belt. The first sensor means
bein~J spaced upstream from said second sensor means along the
direction of travel of said belts. Delivery means feed singu-
lated articles that reach that seconcl sensor means to an out-
put and separator means inhibit the transfer of more than one
article at a time into the delivery stage from the input stage
and hold at the first sensor means all but one article that
enters the delivery stage. Control means selectively operates
the holding means in response to signals from the sensor means.
The control means operat~s in a cycle begir,ning at time = 0,
defined as the time the second sensor means detects the absence
of an article on the belt, wherein: (a) if the first sensor
means detects the absence of an article time = 0, the control
means activates the first holding means at time = T1 for
delivery of at least one article into the delivery stage to
the first sensor means to cause the control mears to deactiv~te
the first holding ~eans and activate the second holding means
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for delivery of a singulated one of the articl~s to the se~ond
sensor means, or, if the first sensor means detects -the presence
of an article at time = 0, the control means activa-tes the
second holding means at time = T2 for delivery to the second
sensor means of the article at said first sensor means to
singulate the article, and (b) the control means deactivates the
second holding means when the second sensor ~eans detects the
singulated article.
In this way the misalignment between two consecutive
articles of the stack may be relatively large before it gives
rise to an erroneGus operation. More particularly, at the
start of a singling operation, i.e. after a stack has heen
brought in the input position the maximum permissible misalign-
ment is substantially e~ual to the distance between the first
driving means and the guiding means comprising a guide plate.
Indeed, when for instance the leading edge of the first of
these two articles makes contact with the guide plate, whilst
the second article is still positioned in front of the first
driving means the latter driving means will be operated, due
to the first detector member being inoperative, so that notwith-
standing this misalignment the first article will be carried
off the stack.
The above mentioned and other objects and features of
the invention will become more apparent and the invention itself
will be best understood by referring to the following description
of an embodiment taken in conjunction with the accompanying
drawings in which:
Fig. 1 is a top view of a singler device according to
the present invention, an electric monitoring circuit forming
part of this device being however not shown;
Fig. 2 is a cross-section along line II-II of Fig. l;
Fig. 3 schematically showc. the electric monitoring
cirCuit according to the present invention;
Figs. 4 and 5 are pulse diagrams to illustrate the
operation of the device.
The singl;er devlce as shown in Figs. 1 and 2 includes
a horizontal bottom plate 1 on which are mounted a vertical
lateral guide plate 2 and an h-shaped front plate 3. These
plates 2 and 3 have cut-out end pc~tions 4 and S respectively.
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An endless perfcrated belt 6 run~ over rc,llers 7, 8, 9 and 10
and between parts of the front plate 3 which are disposed in
the plane of the belt 6. The guide rollers 7, 8 and 9 are idlers
mounted on axles fixed on the bottom plate 1, whilst roller 10
is a drive roller mounted on a shaft 11 of a drive motor (not
shown). A feeler 12 of a microswitch is mounted between lower
portions of the front plate 3 to which strips 4~" 45 made of a
friction material are affixed. Suction devices 13 and 14 are
secured to the front plate 3 and have suction openings 15 and 16
terminating behind the belt. These suction devices
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are for instance diaphragm valves of the type disclosed in
srltish patent 1 225 562 (R. Debackere - W. Mens 5-43, Each
of these suction devices is able to create an underpressure or
not in its suction apening.
The bottom plate 1, the lateral guide plate 2, the
front plate 3 and a portion of the belt 6 define an input
position 17 for a stack 18 of letters or other flat articles.
This stack 18 is urged gently towards the working face of
the perforated belt 6, for instance by means of a pusher plate
(not shown) such as described and shown in the above mentioned
US patent 2 970 834 and aided by three auxiliary feeder belts
41, 42, 43 with their working faces supporting the letters ru~ning
toward and transversaly of the working surface of the suction
belt 6. The motor (not shown) driving the feeder belts 41, 42,
43 is controlled by the microswitch feeler 12.
The input position 17 communicates with a delivery
position 19 via a passage 20 delimited by the portion of the
belt 6 located in front of the cut-out portion 5 of front plate
3 and the end portion of the lateral guide plate 2. A separator
20 21 comprising a freely rotatable vert.ical piece having a sub-
stantially L-shaped cross-section is mounted on the bottom plate
1 and in the cut-out portion 4 of the lateral guide plate 2. By
not shown spring means the separator 21 is continuously urged into
contact with the portion of the belt 6 located in front of the
cut-out portion 5 so as to normally close t.he above passage 20.
Considered in the direction of advancement of the
belt 6 the separator 21 is followed by a suction chamber 22
wherein an underpressure is continuously created and by a
pressure roller 23. The latter roller 23 is an idler roller
mounted on a bracket 24 which is able to pivot about axle
25 fixed on bottom plate 1 and connected to a fixed pin 26
through a spring 27 which continuously urges the roller 23 into
contact with the belt 6.
The delivery position 19 also includes two el~ctric
detector members each comprising a light emitting dio~e and a
photocell mounted in front of each other above the belt and at
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ei~her side thereof. Light emitting diodes 28 and 29 are mounted
on brackets 30 ~nd 31 respectively, whilst photocells 32 and 33
are mounted on the supports 34 and 35 respectively~
Finally, the delivery position 19 is followed by
a pair of belts 36, 37 carried by rollers 38 and 39, 40
respectively, the belts moving in the direction of the arrows.
~eferring to Fig. 3 the electric monit~ring circuit
shown therein includes : i
- bistable circuits Kl and K2 controlling the suction devices
13 and 14 respectively;
- monostable circuits MS1 and MS2 with time constants Tl and
T2 respectively;
- a differentiator D;
- AND-gates Gl, G2, G3 and OR-gates Ml and M2;
- a start key SK connected to an operating voltage V.
The operation of the above described singler device
is described hereinafter by making reference to Figs. 1 to 3
and to Figs. 4 and 5.
Hereby it is supposed that initially no letters
are present in the device so that both the photocells 32 and 33
are illuminated by their associated light emitter diodes 28 and
29 respectively as a consequence of which both the inverse
outputs fl and f2 of these photocells are activated (or on 1).
After a stack 18 of letters has been put in the
input position 17 the start key SK (Fig. 3) is temporarily
operated to trigger the monostable circuit MSl to its unstable
condition via the OR-gate Ml and the AND-gate Gl which is
enabled due to the inverse output fl being activated. After
a time interval Tl has elapsed the O-output of the monostable
circuit MSl becomes activated, as a conæe ~ nce of which the
bistable circuit Kl is triggered to its l-condition wherein it
operates the suction device 13 (Fig. 4). This device then exerts
a suction in the suction opening 15 so that the suction belt 6
starts moving the terminal letter off the stac~ 18 sideways
from the input position 17 into the delivery position l9 against
the action of the friction strips 44, 45. Hereby the leading
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edge of this terminal letter is displaced past the separator 21
and in front o~ the suction chamber 22, both these elements
restraining advancement by the belt 6 of all but this terminal
letter. Thus, letters which are possibly erroneously displace~
5 with this terminal ~ tter, e.g. due to the fact that they adhere
thereto by friction, are substantially prevented from entering
the delivery position 19.
When the leading end portion of the terminal letter
is detected by the photocell 32 the output fl thereof becomes
10 activated as a consequence of which the bistable circuit Kl is
reset to its O-condition. ~lso the suction device 13 then
becomes inoperative. However, simultaneou~ly with the bistable
circuit Kl being reset the bistable circuit K2 is triggered to
its l-condition via the AND-gate G3 and the OR-gate M2 as the
l-output kl of the bistable circuit Kl is then still activated.
Due to this the suction device 14 is then operated so that the
perforated belt 6 displaces the above terminal letter further
into the delivery position 19 from the suction chamber 22 towards
the presure roller 23.
When the leading edge of this letter is detected
by the photocell 33 the output f2 thereof becomes activated as
a consequence of which the bistable circuit K2 is reset to its
O-condition (Fig. 4). Also the suction device 14 then becomes
inoperative. However, at that moment the leading edge of the
terminal letter is seized between the pressure roller ~3 and
the belt 6 and carried further until it is seized between the
belts 36 and 37.
Upon the rear edge of the terminal letter leaving
the photocell 33 the inverse output f2 thereof becomes activated
so that a trigger pulse is produced at the output of the
differentiatorlD and therefore at the output of the OR-gate Ml.
As a consequence either the monostable circuit MSl or the
monostable circuit MS2 is triggered to its l-condition via the
AND-gate Gl or G2 depending on the output 1 or fl of the
photocell 32 being activated at that moment respectively i.e.
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on a letter following the above mentioned terminal letter,
hereinafter called second letter, ~eing absent or present in
front of this photocell 32 raspectively.
Normally, no such sacond letter is located in
front of the photocell 32 and in this case the operation is a5
described above.
On the contrary when such a second letter is located
in front of this photocell 32 due to the fact that it has for
instance been carried off the stacX together with the above
mentioned terminal letter, the monostable circuit MS2 is
triggered to its unstable condition (Fig. 5). After a time
interval T2 has elapsed the O-output of the monostable circuit
MS2 becomes act~vated as a consequence of which the bistable
circuit K2 is triggered to its l-condition wherein it operates
the suction device 14 so that the perforated belt 6 displaces
the above second letter further into the delivexy position.
The rest of the operation is as ~lready described above.
The reason of the above mentioned time intervals
Tl and T2 is explained hereinafter. Hereby reference is made
to Figs. 4 and 5 wherein the length of the terminal letter
corresponds to a time interval TL.
The distance between two consecutive letters,
such as the above mentioned terminal letter and second letter,
must at least be equal to a minimum value in order that
sufficient time should be available to perform other operations,
such as for instance the control of a points mechanism. This
distance is supposed to correspond to a time interval T, taking
the operation speed into account. This means that the time
interval elapsing between the moment at which the trailing edge
of the terminal letter leaves the photocell 33 and the moment
at which the suction device 13 (Fig. 4) or 14 (Fig. 5) is operated
to displace the second letter should be such that the leading
edge of this second letter comes in front of the photocell 33
after a time interval T.
As described abo~e the suction device 13 -is operated
when the second letter is not located in front of the photocell
32 at the moment the terminal letter leaves photocell 33. This
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second ~er is c~ ~ ~ tothe photocell 32 when its ~ading ed~e is abDut
~ come ~ ~n~ ofthis phd~oell 32a S~ppOS~ inthiscaæ atime int~al
T3 t~.~) i5 ~qu~d to reach the photocell 33 it is clearthat instead
of operating th~ suction device 13 only a time interval T after
the trailing edge of the terminal letter has left the photocell
33, in which case the second letter would onl~ reach the photocell
after a time interval T + T3, this suction device 13 can already
be operated a time interval Tl = T-T3 after the trailing edge
of the terminal letter has left the photocell 33. In this ca~e
the second letter will reach the photocell 33 after the minimum
time interval T. Thus the operating speed of the device is
increased.
As also described above, the suction device 14 is
operated when the second letter is located in front of the
photocell 32. This letter is closest to the photocell 33 when
its leading end portion is about to come in front of the latter
photocell e.g. when it is at about 5mm from the photocell 33 which
is in line with the point at which the pressure roller 23 makes
contact with the belt 6. Because in this case a time interval
T4 is required to reach the photocell 33 it is clear that when the
suction device 14 is operated a time interval T2 = T-T4 after
the trailing edge of the terminal letter has left the photocell 33
the second letter will again reach the photocell 33 after the
minimum time interval T has elapsed.
The minimum letter length able to be correctly
processed is considered hereinafter.
As described above, if the second letter is not
located in front of the photocell 32 at the moment the trailing
edge of the terminal letter leaves the photocell 33 the second
letter will be advanced, a time interval Tl later, by the
cooperation of the belt 6 and the suction device 13. This means
that at the moment the leading edge of this second letter is
in front of the photocell 32 the trailing edge of this letter
should still be completely in front of the suction device 13
in order to prevent a third letter following the second letter
to be displaced by this suction device. Hence, the minimum
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letter length able to be processed by the present device is
substantially equal to the distance separating the suction
device 13 and the photocell 32.
Similarly and as also described above, if the
second letter is located in front of the photocell 32 at the
moment the trailing edge of the terminal letter leaves the
photocell 33 the second letter will be advanced, a time interval
T2 later, by the cooperation of the belt 6 and the suction
device 14. This means that at the moment the leading edge o~
this second letter is in front of the photocell 33 the trailing
edge of this letter should still be completely in front of the
suction device 14 in order to prevent a third letter following
the second one to be displaced by this suction device. Hence,
the minimum letter length able to be processed by the present
device is also substantially equal to the distance between the
trailing end portion of the suction device 14 and the photocell
33.
The choice of the relative position of the suction
devices 13, 14 and of the photocells 32, 33 will be e~plained
hereinafter.
At the start of an operation the maximum permissible
misalignment of the front edges of the letters of the stack 18
is equal to the distance between the leading edge of the suction
device 13 and the guide plate 2 because when the leading edge
of a first letter coincides with the leading edge of the suction
device 13 and the leading edge of the second letter following
the first one makes contact with the guide plate the suction
device 13 will be operated because no letter is situated in front
of the photocell 32, so that - as it should be - the first
letter will be carried off the stack 18 by the belt 6. On the
contrary, if the misalignement is larger the seaond letter
instead of the first one will be displaced from the input
position towards the delivery position 19~ It is clear that
to have the ma~imum permissible misalignment at the start of
an operation the distance between the suction device 13 and
the guide plate 2 should be a maximum i.e. the plate 2 should
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be mounted as close to the photocell 32 as possible. However,
the distance between the guide plate 2 and the photocell 32 should
be sufficient to mount the sep~rator 21 and the suction chamber
22 so that this limits the maximum permissible alignment.
During operation the maximum permissible misalignment
of the front end portions of the letters of the stacks 18 ls
somewhat smaller than that at the start of an operation because
of the space required by the suction device 14. Indeed, this
misalignment is equal to the distance between the leading edge
10 of the suction device 14 and the photocell 32 because when the
leading edge of a first letter coincides with the leading edge
of the suction device 14 and the leading edge of the second letter
following the first one is situated in front of the photocell 32
the suction device 1~ will be operated~ so that - as it should
be- the first letter will be carried off the stack by the belt
6. On the contrary, if the misalignment is larger the second
letter instead of the first will be displaced towards the
delivery position 19.
It is clear that to have the maximum permissible misalignment
during operation the distance between the suction device 14
and the photocell 32 should be a maximum i.e. the suction device
14 should be as close as possible to suction device 13. But
since the distance between the suction device 14 and the photocell
33 is equal to the minimum letter length this means that the
photocell 33 should also be as close as possible to the photocell
32. However between the photocells 32 and 33 sufficient room
should be provided to mount the elements 21, 22 and 23.
Since vibrations introduced by the driving mechanism
and particularly the rollers can create excessive noise, it is
desirable to reduce them by making the bottom plate 1 out of
a suitable vibration damping material. The following sandwich
material composition comprising two metal layers enclosing a
layer of organic material produced adequate results :
- 3 to 10 millimeters, e.g. 10 millimeters of aluminium;
- 1 to 3 millimeters, e.g. 1 millimeter, of lead;
- 0.2 to 2 millimeters, e.g. 0.5 millimeter of soft
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polyvinylchloride.
So~t polyvinylchloride has a hardness between
60 and 80 Shore A.
While the principles o~ the invention have been
described above in connection with specific apparatus, it is
to be clearly understood that this description i9 made only by
way of example and not as a limitation on the scope of the
invention.
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