Note: Descriptions are shown in the official language in which they were submitted.
CA 02212042 1997-07-31
Jam monitoring device for a transport device
for paper, especially for a paper tape
s
This il~vention relates to a jam monitoring device for a transport device for
paper, especially for a paper web with at least one drive roller and a freely
rotatable pressure roller ~rranged axially parallel thereto, wherein the paper is
passed between the two rollers and is pressed on to the drive roller by the
o pressure roller.
In paper handling m;achines, e.g. an automatic account post-processing
installation which is connected downstream of a laser printer, a paper jam can
occur for all sorts of reasons. In order then to avoid damage from this what is
needed is to recognise a paper jam immediately and then stop the m~chine. ~lL
15 one previously known jam monitoring device the monitoring of a paper which isperforated at the edge is effected by monitoring the perforated edge by means ofa light barrier arranged in ~is region. If its light beam is no longer inlell~led at
regular intervals, because of a paper jam, the light barrier causes the m~chine to
stop. However, such a jam monitoring device is only suitable for paper webs
20 which have a perforated ,edge at the side. In order to guide such a perforated
paper web, a tractor drive with pin-feed bands eng~ging in the perforations is
necessary, while the mutual spacing of pin-feed bands has to be adjustable in
width for plaper webs of di~elellt widths. The monitoring device is made more
expensive by ~hese tractars. Since a paper web without a perforated edge at the
25 side can in no way be monitored by the known jam monitoring device, there is
the further disadvantage that in an area subsequent to the removal
CA 02212042 1997-07-31
of the perforated edge, jam monitoring is no longer possible.
The inLvention is therefore based on the object of providing a jam monitoring
device for a transport de~vice for paper, especially for a paper web, of the kind
initially referred to, with a simple, inexpensive structure, which makes it possible
5 also to monitor a non-perforated paper web and if required also sequPnti~lly
following single sheets of paper.
This is achieved according to the invention in that a stationary sensor is
associated wi~ each of the drive roller and the pressure roller for separate
monitoring of the speeds of these rollers, and in that an ev~ fing circuit is
o provided to compare the signals issued by the two sensors per unit time or unit of
feed and to issue an error signal on deviation from a preclel~ ed ratio of the
signals issuing from the sensors.
The invention is thus based on the concept of continuously monitoring the
speed of the pressure rollLer by means of a sensor and comparing it with that of15 the drive roller. When ~e paper transport is free from disturbance, ~e drive
roller drives the paper web pressed thereon by the pressure roller. The pressureroller rolls on the paper ~eb and is driven by the paper web at a peripheral speed
which corresponds to the peripheral speed of the drive roller, apart from
negligible slip. With passage of the paper without disturbance, a certain number20 of signa]Ls from the sensor of the pressure roll is associated with the signals
issuing from ~e sensor of the drive rollLer, i.e. the signals are in a specific
CA 02212042 1997-07-31
ratio to one another. Since this ratio corresponds to a predel~l "~ ed ratio
programm~ed into the ev~ ~in~ circuit, the evaluating circuit does not issue anyerror signal so long as the paper passes without disturbance. However the
movement of the paper ~veb is slowed down or stopped by a paper jam. The
5 peripheral speed or speed of rotation of the pressure roller driven by the paper
web falls corresponding]y or becomes zero, while the drive the roller carries ontllrning with the predetelmined drive speed. With the retardation of the speed of
the pressure roller, the number of signals issued by the associated sensor reduces
and so does the ratio to the signals issued by the sensor of the drive roller. The
o evalllating circuit recognises this deviation from the predel~ i,led ratio andissues an error signal indlicating the disturbance, which effects stopping of the
transport device and optionally of fur~er preceding and succeeding units.
The jam monitoring device according to the invention is distin~li.shed by a
particularly simple structure and facilitates cost-effective m~mlf~cture. It is
15 suitable for any width of paper web without adjustment. Both perforated paperwebs and paper webs without a perforated edge can be monitored thereby. Jam
monitoring of individual paper sheets following one another is also possible in a
development of the invention.
Advantageous arrangements of the invention are characterized in the
20 dependent claims.
The invention will be explained in more detail below, with reference to ~bLe
embodiments shown in tlhLe drawings.
CA 02212042 1997-07-31
These show:
Figure 1, a side view of a first embodiment of the jam monitoring device,
Figure 2, a plan vie~v in the direction II in Figure 1,
Figure 3, a further e:mbodiment in side view.
The drive roller 1 of a transport device for a paper web 2 is driven by a
motor 13 in the indicated direction A. A freely rotatable pressure roller 3 is
provided on the other side of the paper web 2 and is arranged axially parallel to
the drive roller 1. The pa~per web 2 is passed between the two rollers 1, 3 and is
pressed on to the drive roller 1 by the pressure roller 3. The drive force of the
o drive roller is thus tr~n~rnittcd to the paper web 2 and the paper web moves in
the paper feed direction B. Guide rails or plates 4 pLev~llL deviation to the sides
of the paper web 2 transverse to its feed direction B.
In order to monitor the speed of the pressure roller 3, a ~rst sensor 5 is
provided. This sensor 5 is advantageously an inductive transducer which
responds to individual metal bodies 6 which are disposed in the pressure roller 3
at equally spaced peripheral angles. When the pressure roller 3 rotates each
metal bod~ 6 provides a signal which is fed from the sensor 5 to an evaluating
circuit 7.
A sensor 8 is associ~ted in like manner with the drive roller 1 and cooperates
with metal bodies 9 in a disk 10 which is for its part fixedly connected to the
drive roller 1. The signals issued by the second sensor 8 are also fed to the
evaluating circuit 7.
CA 02212042 1997-07-31
During paper feed fiee from disturbance the paper web 2 is driven by the
drive roller 1 and the paper web 2 in turn entrains the pressure roller 3. With
paper feed free from disl;urbance, the peripheral speeds of the two rollers 1, 3 are
equal in m~gnihl~le and lhe numbers of signals issued to the ev~ ting circuit 7
5 by the two sensors 5, 8 stand in a specific ratio, which corresponds to a
predetermined ratio programmedl into the evaluating circuit 7. The ev~hl~qting
circuit accordingly does not react.
If however disturbance with the paper feed occurs, the movement of the
paper web 2 slows down or it is stopped completely. Accordingly the speed of
o the pressure roller 3 driven by the paper web 2 also falls, while the drive roller 1
driven by Ihe motor 13 with a predele~ ed speed of rotation carries on tllrning
This changes the ratio of the signals issued by the sensors S and 8 per unit of
time or feed. This deviation from the predetermined, programmed ratio is
detected by the evaluatinLg circuit 7 and this generates an error signal at its output
S 7a indicating the disturba~Lce. The motor 13 is stopped by ~is error signal and
possibly also further units preceding and succeeding the transport device.
The further arrangement of the invention shown in Figure 3 serves to
monitor individual sheets of paper following one another. The drive roller 1
shown at the far left and the pressure roller 3 associated therewith, as well as the
20 motor 13 correspond in their construction and in their mode of operation to the
parts described in connection with the description of Figures 1 and 2. A sensor 5
is likewise associated with the pressure roller 3 and
CA 02212042 1997-07-31
a sensor 8 with the drive roller 1. The signals issued by the two sensors 5, 8 are
likewise fed to an ev~ ng circuit 7. The preceding description therefore
applies in general to the embodiment shown in Figure 3. Since individual paper
sheets fol]Lowing one another are to be monitored with this transport device
5 shown in Figure 3, filr~er pressure rollers 3' are provided spaced from one
another in the paper feed direction B of the paper sheets, with each of which a
sensor 5' is associated. The signals issued by the sensors 5' are a]Lso fed to the
ev~ tin~ circuit 7. The mutual spacing a of the pressure rollers 3 and 3' shouldbe less than the format height of the paper sheets. The drive roller 1 drives atl0 least one endless transport belt 12 which is passed beneath the further pressure
rollers 3'. A backing roller 14 supporting the transport belt 12 is arranged in the
region of each fur~er pressure roller 3'.
If a paper jam occurs between any adjacent pair of pressure rollers 3 or 3' so
that the movement of the paper sheet passing below the pressure roller 3 or 3'
lS involved is slowed down or stopped, then the speed of the corresponding
pressure roller 3 or 3' reduces or it falls to zero. On the other hand, the drive
roller 1 and the transport belt 12 are driven on at the operating speed. The ra~o
of the signals issued by the sensor 8 and by the sensor 5 or 5' of the retarded or
stopped pressure roller 3 or 3' changes through this. The evaluating circuit 7
20 recognises this and stops ~e motor 13.
