[0001] The invention refers to an automatic opening device at the end of the paper in the
thermal printers. Currently, in many thermal printers, the approach of paper end is
reported by one or more lines of different colours on the final part of the paper
roll. To appear of the beginning of the coloured lines, often, the roll is changed
with waste of the no used thermal paper. This repeated preventive substitution, for
example in a supermarket, depending on the cash desk operativeness and for the number
of cash desks in operation, determines a high thermal paper waste. Other systems are
known to signal the paper end via warning light onto the printer and/or signalling
to monitor. To notice the warning light or the signalling to monitor may be difficult
and may increase the times of thermal paper change. In fact, in identifying which
printer is out of paper, having often connected with the monitor over to the printer
for cash voucher also printers for credit card payments, POS or other kind of cart
or printers for fiscal aims, and to open the cover to place the thermal paper roll,
determines a further operation with lost of time for the operator that increases the
time wait at the cash desks for the clients. Moreover, with the known systems, it
is possible that, ended the paper and with the printer still in working, the thermal
head comes in direct contact with the under rubber printing roll. In this situation,
the crawling of the thermal head onto the rubber printing roll generates a wear and
tear of the same head. Aim of the present invention is to avoid the above cited drawbacks.
The invention, in fact, shows in clear and prompt way in which printer the paper is
ended. Moreover, such as the printing roll is generally placed onto the cover of the
container of the thermal paper roll, to open automatically said cover it is avoided
that the head crawls onto the rubber roll without the paper present between them.
Other advantage is related to the determination of the printer out of thermal paper
and the prompt introduction of the thermal paper such as the printer cover is already
opened with thermal paper roll changing time quick. These and others aims and advantages
of the invention are better understood to the description of a preferred but not exclusive
embodiment as follows and to the enclosed drawings of sheets 1, 2, 3 and 4. In particular
in sheet 1 figure 1 is perspective lateral view of a printer in which the invented
device is mounted and without the outside protection covering. Figure 2 is perspective
other side view of a printer in which the invented device is mounted. In sheet 2 -
figure 3 is perspective view of a printer with the invented device. Figure 4 is view
of the parts which generate the unfastening. In sheet 3 figure 5 is perspective view
with section parts of the main rotating devices in the step of fastened cover. Figure
6 is perspective view with section part of the main rotating devices in the step of
unfastening cover. In sheet 4 figure 7 is perspective view of a printer with the invented
device in step of automatic opening of the cover at the thermal paper end. The figure
8 is perspective view of a paper with the invented device with the cover opened so
to fit in a new thermal paper roll. The printer consists of a printing roll 1 inserted
into a cover 2 equipped with and automatic opening device 3 that determines the cover
opening at the paper end. In an embodiment said automatic opening device 3 consists
of a paper end sensor 4 connected to an electric motor 5. The paper end sensor 4 starts
the electric motor reversed its direction of rotation in comparison with the direction
of rotation had during the printing step. The electric motor 5 is equipped with a
gear wheel 6 placed onto a drive shaft. The gear wheel 6 is connected to a timing
belt 7. The timing belt 7 drags a further gear wheel 8. Onto the same rotation pin
9 and integral with the further gear wheel 8 a third gear wheel 10 is provided. This
third gear wheel 10 engages onto an other gear wheel 11 integral with to the outside
protruding part 12 of the printing roll 13. At the other end of the printing roll
13 is present an other gear wheel 14. Said gear wheel 14, so placed onto the other
side of the thermal printer, is placed onto a pin 15. Coaxially to the pin 15, and
puts between the gear wheel 14, a radial bearing 16 is present that gives the angular
motion only in a direction of rotation. Said radial bearing 16 in the normal step
of printing lets free the gear wheel 14 but, when the printing roll 13 rotates in
the opposite direction in comparison to the direction of rotation had during the printing,
comes to move the gear wheel 14 that puts in rotation an other gear wheel 17. On the
same axis, but on parallel vertical plane, is present an other gear wheel 18 that
engages onto a further gear wheel 19. On the same shaft and integral with the gear
wheel 19 a cam 20 is provided. Said cam 20 is in touch with the pin 21 of the unfastening
teeth 22 that open/close the cover 2. The unfastening teeth 22 are inserted in the
manual unfastening levers 23 to help the lifting of the cover 2. Then, the cover 2
has hinges 24 with coil springs 25. In working, ending the paper of the roll present
inside the printer, the end paper sensor 4 comes to activate. The end paper sensor
4 gives, by normal connections and parts, the impulse to the electric motor 5. The
impulse given to the sensor 4 starts the inversion of the rotation motion of the electric
motor 5 normally used for the rotation of the printing roll. The motion inversion
determines, by the rotation given to the printing roll 13 to the gear wheel 14, the
rotation of the gear wheels 17, 18 and 19 with rotation of the cam 20. Said cam 20
rotating moves the pin 21 and actuates the unfastening of the unfastening teeth 22
connected with the unfastening levers 23. So the cover 2 comes to unfasten and it
is put in opening by the springs 25. With the cover in opening, with the same actuated
in automatic way, it is put in evidence to the operator the lack of thermal paper
inside the printer. So it is immediate and quick the withdrawal of the paper support
and the fitting up of a new thermal paper roll inside the printer. In this way the
thermal paper is used in whole and such us the cover 2, that contains the printing
roll 1, immediately raises when the paper is ended, it is not possible the friction
of the thermal head onto the printing roll 1 so avoiding to damage the same head.
Inserted the paper the cover 2 is closed again so that the pin 21 crawls onto the
cam 20 making it rotates. In this way the printer turns in working while the automatic
opening device 3 prepares itself for the subsequent opening when the paper will be
ended again. In an other embodiment, always falls within the present inventive concept,
the automatic opening device can be provided with electrical, mechanical or pneumatic
components and motorized to be realized to the person skilled in the art on the base
of the details described and illustrated and with the same aim, substituting the technical
details with other equivalent and with the same functions.
