Device for conveying printed sheets in an installation for checking the quality of paper money

The device comprises a conveyor chain (1) for the sheets to be checked (3) by a detector (5). The support bars (4, 4'), on which the sheet to be examined (3) slides, are fitted, in the checking zone, with suction nozzles (4a) and in the gap between two support bars (4) there are provided movable arms (10), fitted at their end with suction nozzles (10a) which, in the operating position, are aligned with the suction nozzles (4a) of the support bars and arranged in the sheet transfer plane in order to hold the sheet to be examined (3) in this plane. In order to prevent the clamps (2a) which pull the sheet (3) from touching the arms (10), a mechansim is provided for tilting the arms (10) when the clamps (2a) pass above these arms.

FIELD OF THE INVENTION 
The present invention relates to a device for conveying printed sheets in 
an installation for checking the quality of paper money, particularly bank 
notes, in a checking zone comprising at least one detector. 
PRIOR ART 
Devices are already known for checking the quality of bank notes. For 
example, Patent FR 1,489,113 describes a method and a device according to 
which non-cut sheets of notes are firstly checked visually in order to 
enable the operator to mark the faulty notes, exhibiting errors in color 
or stains. The sheets are then cut into notes which pass on a first 
cylinder in front of detectors checking the side of the note facing 
outward and reacting to the checking marks borne by the notes, as well as 
to the errors in the centering of the print. The notes are then 
transferred to a second cylinder where detectors check the other side. The 
faulty notes are automatically picked out of the conveyor chain and 
replaced by faultless notes. Finally, an automatic installation makes it 
possible to count the checked notes and to pack them in the form of wads. 
With the latest developed techniques, the requirements for checking the 
quality of recently printed notes are increasing more and more. The 
detectors which pick up the details of register, of color, of ink 
variation, of faults such as stains, spoils, etc. are becoming 
increasingly sophisticated which results in very strict requirements 
regarding the position of the sheets to be examined with respect to said 
detectors, the sheets having to be kept at a very precise distance from 
the detector. In a parallel patent application, the applicant has already 
proposed a conveying cylinder fulfilling these requirements. 
A complete quality check must also comprise a check of transparency or 
check by reflection in order to examine, in particular, the position of 
the water mark, of the safeguarding thread, and all the other criteria 
which can be verified by transparency or reflection. In order to carry out 
these checks, the sheets must be in the plane state, and therefore must be 
brought on a conveyor chain fitted with clamps which grasp the front edge 
of the sheet in order to make it pass in front of the system for detection 
by transparency, or reflection, while said sheet slides in the transfer 
plane. 
It became clear that the sheets grasped by the clamps, with a relatively 
high speed of conveyance, of the order of 2.8 meters per second, tend not 
to adhere securely to the support. Indeed, the sheets to be examined which 
have also been printed in intaglio, exhibit very sizeable deformations due 
to the striking force during the printing and their surface exhibits 
undulations which, added to the aerodynamic effects created by the speed 
of conveyance of the sheets, produce conditions which are unacceptable for 
an accurate scanning, considering the precision of current detectors. For 
the transparency check, it is therefore essential that this sheet, at 
least while it passes under the detector, remains in its perfectly plane 
state, without forming undulations, because the distance between the 
detector and the checking zone in which the sheet is located must remain 
constant with a predetermined tolerance, for example of approximately 
.+-.0.3 mm. 
SUMMARY OF THE INVENTION 
The present invention proposes to build a conveyor chain device which 
guarantees that the sheet assumes a perfectly plane state while it passes 
in front of the detector system, without any risk of damaging the print 
recently produced on the sheets. 
The advantage of this device is to enable the printed sheet to be securely 
held by the vacuum system in the transfer plane defined by the support 
bars, when it passes below the detector, while avoiding a collision 
between the suction nozzles and the clamps when the latter draw level with 
the nozzles.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the depicted installation for detection, the conveyor chain 1 is fitted 
with bars 2 with clamps 2a for gripping the front edge of each of the 
sheets to be examined 3 and sliding them over a support formed by support 
bars 4, 4', between a detector 5 and a lamp 8. The support bars 4, 4' 
extend longitudinally in the direction of conveyance and are separated by 
a distance of approximately 15 to 20 mm. The clamps 2a which grip the 
sheets and which are, for example, twelve in number, move partially into 
the gaps between the support bars. All the sheets, only one of which is 
depicted in the figure, follow on one behind the other at set and constant 
intervals. 
The detector 5 is used for checking transparency, that is to say for 
checking the existence of details and of characteristics which appear only 
by transparency. For this purpose, the support bars 4, 4' are provided 
with a slit 6 located in the zone for checking the sheet, the bars located 
in front of the sheet 6 are denoted by the reference 4 while those located 
after the slit are denoted by the reference 4'. The lamp 8, placed below 
this slit 6 and the plane of the support bars 4, 4' in the reading 
direction 7 of the detector 5, makes it possible to illuminate the zone to 
be examined through the slit 6. This checking zone is in the shape of a 
line transverse to the direction of conveyance of the sheets. 
In order to prevent the sheet to be examined 3 from coming off the support 
bars 4, an air blower is provided by means of a bar 9, with nozzles 9a 
directed toward the sheet 3 in the region of the slit 6. 
In order to hold the sheet to be examined 3 securely in the checking zone 
in a plane state, at a constant distance from the detector 5 and with a 
tolerance of .+-.0.3 mm, the support bars 4 are provided at their end 
limiting the front of the slit 6, with suction nozzles 4a aligned in a 
transverse line located in the checking zone. In addition, in the space 
existing between the support bars 4, there are mounted movable arms 10 
fitted with nozzles 10a at their end. In the operating position, the 
nozzles 10a and 4a form a single suction line arranged transversely to the 
direction of conveyance of the sheets, this suction line being located in 
the sheet transfer plane. The auxiliary suction nozzles 10a are in fact 
necessary for guaranteeing that the sheets are in a perfectly plane state 
in the checking zone and preventing any risk of deformation in the spaces 
between the support bars 4. By thus inserting movable arms 10 between the 
support bars 4, the clear distance between the bars and said adjacent arms 
is reduced to only 0.5 to 1 mm. 
The nozzles 4a of the support bars 4 are linked to a vacuum system (not 
shown) and the nozzles 10a are linked to a vacuum conduit 11 which is 
itself also linked to this vacuum system; the vacuum force is adjusted so 
that the suction enables the sheet to be held securely without 
deformation. The connection between the nozzles 4a and the vacuum is not 
shown on the drawing. 
In order to prevent a clamp 2a from touching the end of the arms 10 fitted 
with the nozzles 10a, a mechanism for actuating these arms is provided. 
The assembly formed by the arms 10 and the vacuum conduit 11 is mounted in 
a movable manner with respect to the support bars 4 and, for this purpose, 
is fixed to the end of a lever with two arms 12a, 12b. This lever 12a, 12b 
is articulated on a stationary spindle 13 and the end of the second am 12b 
is linked by an articulation 14 on a transmission bar 15 the other end of 
which is itself linked by an articulation 16 to the end of a control lever 
17. The control lever 17 is mounted on a fixed pivot 18 and is firmly 
attached to a lever arm 19 which is itself also articulated on the pivot 
18. A follower roller 19a, which interacts with a cam 20, with its lobe 
20a, is mounted at the free end of the lever arm 19. This cam 20 is 
mounted on a shaft 20b, the rotation of which is synchronized with the 
speed of forward motion of the chain 1 in such a way that the cam 20 
completes one revolution while the chain 1 moves forward by the length of 
a gap between two bars 2 with clamps, therefore between two successive 
sheets. The other end of the control lever 17 is articulated at 21 to a 
threaded rod 22 fitted at its end with a stop-piece 26 which bears against 
a fixed stop-piece 23. A return spring 24 acting in compression and 
mounted between the fixed stop-piece 23 and a collar 25 enables the 
follower roller 19a to be pressed against the surface of the cam 20. The 
operating position depicted in FIGS. 1 and 3 is defined by the contact of 
said stop-pieces 23, 26, and may be adjusted by changing the position of 
the stop-piece 26 on the threaded rod 22 on which it is screwed. 
The shape of the cam 20 and the synchronization of the movements of 
rotation of the shaft 20b and of the forward motion of the chain 1 are 
such that the arms 20 remain in their operating position, that is with the 
nozzles 10a aligned and in the same plane as the nozzles 4a of the support 
bars 4 during the whole time that the sheet 3 passes above the slit 6, and 
therefore in the checking zone where it is securely held in the transfer 
plane by the action of the suction nozzles 4a, 10a. When the clamps 2a 
draw level with the slit 6, the cam 20, with its lobe 20a, tilts the lever 
17, against the action of the spring 24, which causes the transmission arm 
15 to move, which in turn causes the bent lever 12a, 12b to tilt about the 
pivot 13, and consequently the ends of the arms 10 with their nozzles 10a 
to move downward. This movement may be, for example, of a few millimeters. 
The clamps 2a are thus prevented from touching the arms 10 while they pass 
across the slit 6. 
As soon as the bar 2 with clamps 2a has travelled past the region of the 
checking zone, the roller 19a has travelled past the lobe 20a of the cam 
20 and the levers 17, 19, under the action of the spring 24, move the arms 
10 back into the operating position via the transmission arm 15 and the 
levers 12a, 12b, this operating position being defined by the stop-piece 
26 bearing against the fixed stop-piece 23. Furthermore, in this operating 
position, it is not necessary for the roller 19a to touch the cam 20 in 
its part which does not include the lobe 20a. 
The invention is not limited to the embodiments described and embodiment 
variants could be added without thereby leaving the scope of the 
invention.