FIELD OF THE INVENTION
The present invention relates to inkjet printing mechanisms,
such as printers or plotters.
- BACKGROUND OF THE INVENTION
More particularly the present invention relates to a
replaceable service station for cleaning an inkjet print head.
Nowadays inkjet printing systems are used in a wide array of
apparatuses in a wide array of applications such as fax, colour
photo printing, industrial applications etc. In these printing
systems inks, possibly of various colours, is ejected out of an
array of nozzles located in a print head to the receiving material.
A long known problem in inkjet printers is that the nozzles through
which the ink is projected to the receiving material are blocked by
clogging of ink inside the nozzles and on the print head. This
renders certain nozzles inoperable and results in a defective print
of deteriorated print quality.
To improve the clarity and contrast of the printed image, recent
research has been focused to improvement of the used inks. To
provide quicker, more waterfast printing with darker blacks and more
vivid colours, pigment based inks have been developed. These
pigment-based inks have a higher solid content than the earlier dye-based
inks. Both types of ink dry quickly, which allows inkjet
printing mechanisms to forms high quality images.
In some industrial applications, such as making of printing plates
using ink-jet processes, inks having special characteristics causing
specific problems. E.g. UV curable inks exist to allow rapid
hardening of inks after printing.
The combination of small nozzles and quick drying ink leaves the
print heads susceptible to clogging, not only from dried ink and
minute dust particles or paper fibres, but also from the solids
within the new ink themselves.
It is known to counteract or correct the problem of clogging by
protecting and cleaning the print head by various methods.
Also other methods exist for cleaning an inkjet print head which may
include applying solvents as in EP-A-1 018 430 ,
- Capping : during non-operational periods the print head can sealed
off from contaminants and prevents drying of the ink. To enhance
priming when printing starts, it is possible to apply a vacuum to
the print head through the capping unit for clearing the nozzles.
- Spitting or Priming: by periodically firing a number of drops of
ink through each nozzle into a waste ink receiver, commonly called a
spittoon, clogs are cleared from the nozzles.
- Wiping : Before an during printing the inkjet print head is wiped
clean by using an elastomeric wiper, removing ink residue, paper
dust and other impurities.
These features designed to clean and to protect a print head , are
commonly concentrated in a service station which is mounted within
the plotter chassis, whereby the print head can be moved over the
station for maintenance. An example of such a service station can
be found in US-A-6 193 353 combining wiping, capping and spitting
A known problem using wiping systems is that the wiper itself
becomes contaminated with ink residue and dust. This decreases the
wiping efficiency and may even cause damage to the print head.
For removal of contaminants from the wiper, the wiper blade is
dragged into contact with a scraper.
Also other methods for cleaning the wiper can be used.
- Use can be made of a sponge-like member for cleaning the wiper
- To facilitate removal of contaminants of the wiper, e.g.
ultrasonic waves can be used.
In some prior art embodiments the scraper is mounted on the plotter
chassis, while the service station is located on a movable sled. A
similar embodiment can be found in US-A-6 155 667.
A problem which is not addressed in the prior art is that
during cleaning of the wiper, the impurities, scraped off, will
contaminate the surrounding area inside the plotter.
Also ink sputtering will happen when the wiper blade touches
the scraper and even so when the wiper blade is jumping back to its
vertical position after release.
Another non-addressed problem is that the impurities which
build up on the wiper/scraper system can contaminate the print head,
especially when changing to another colour or to another type or
ink. A residue of the old ink collected on the wiper and scraper
from previous printing and cleaning actions can be deposited on the
print head causing contamination of the new ink by old residue
causing colour deviations of the newly printed image or leading to
problems caused by e.g. chemical incompatibility of the old and new
The internal contamination can result in deteriorated printing
quality and extra need for maintenance for cleaning the inside of
the inkjet printing mechanism. A need exists to enable easy and
complete changing of the print head cleaning system.
- OBJECTS OF THE INVENTION
Another problem is that the efficiency of the scraper will
decrease in time due to dried ink deposals on the scraper tip.
Periodically the scraper has to be cleaned or replaced.
It is an object of the present invention to provide a service
station for use in an inkjet printer causing less contamination
inside the printing engine.
It is a further object of the invention to provide a service
station which can be easily replaced upon changing the printhead or
- SUMMARY OF THE INVENTION
It is a further embodiment of the invention to provide
efficient removal of accumulated residue form the inkjet printing
The objects of the invention are realised by a service station
having the specific features of claim 1. Specific features of
preferred embodiments are set out in the dependent claims.
- BRIEF DESCRIPTION OF THE DRAWINGS
A method for cleaning a wiper of a service station is set out
in claim 12.
- DETAILED DESCRIPTION OF THE INVENTION
- Fig. 1 shows service stations according to the present invention in
a dual head printer.
- Fig. 2A illustrates a service station according to the invention with
a retraction mechanism for the wiper system with the wiper
system in wiping position.
- Fig. 2B illustrates the service station with the wiper system in
retracted position with the wiper blades in a position past
- Fig. 3 shows the actuation of the moving mechanism of a possible
embodiment according to the invention by an external motor
during cleaning of the wiper.
- Fig. 4 shows an embodiment having plural service stations wherein
the wipers are mounted on an axis.
- Fig. 5A shows a possible embodiment of a cleaning station wherein a
rotational movement is used for cleaning the wiper.
- Fig. 5B shows the the position of the rotatable wiper system after
rotation past the scraper.
- Fig. 6 illustrates the rotation of the wiper by the external motor.
- Fig. 7 depicts a service station with means for removing residue
from the enclosure.
While the present invention will hereinafter be described in
connection with preferred embodiments thereof, it will be understood
that it is not intended to limit the invention to those embodiments.
Fig 1 depicts dual service stations 1 according to the present
invention. When using a single print head only one station is
needed. In a printer using several print heads plural cleaning
stations can be provided. Each service station 1 comprises an
enclosure 2, a capping system 3 for covering the ink jet print head
(not shown) during non printing periods. On the upper side of the
enclosure 2 is provided an aperture 4 shown with a protruding wiper
system 5 in the operable position, consisting of two wiper blades 6.
During wiping of the print head (not shown) the wiper system 5 is
dragged in contact along the print head whereby ink residue and
other impurities are collected by the wiper blades 6.
The enclosure 2 can be executed in all sorts of material.
Preferably use is made of a plastic material so that the enclosure 2
or its parts may be cheaply made by e.g. an injection-moulding
technique. The enclosure 2 can be completely closed but can also be
partially open. The enclosure 2 is provided with a system enabling
easy mounting and removal of the service station 1 in the printer.
In Fig 1 the service station 1 is provided with a mounting plate 7
with mounting holes 8 enabling easy mounting of the service
station 1 using e.g. screws or other means for fastening. Other
systems such as clip-on systems, clamps etc. can also be used.
The wiper blades 6 are preferably made from an elastomeric material
in order to ensure good contact with the print head during wiping.
The hardness of the wiper blades 6 is preferably within the range of
60-80 Shore A. The tip op the wiper blades 6 may be asymmetrical or
grooved in order to provide good wiping of the print head and
efficient collection of the ink residue and impurities.
The orientation of the wiper blades 6 may be perpendicular to the
wiping direction of the wiper system 5. In an alternative
configuration at least one of the wiper blades 6 is mounted at an
oblique angle to the wiping direction propagating the collection of
impurities at the trailing edge of the wiper blade 6.
In following description reference is made to Fig. 2A en 2B
depicting a section of the servicing station 1.
Inside the enclosure 2 of the service station 1 is provided a
scraper 9 for cleaning the wiper blades 6. The scraper 9 can be
integrated at the inside of enclosure 2. The scraper 9 is positioned
at a lower level inside the service station 1, so that the cleaning
operation is completely realised internally in the service
station 1. The scraper 9 can be constituted in the same material as
the enclosure 2 itself and can even be manufactured during the same
production process. Other materials can be used, while also various
methods for mounting the scraper 9 inside the enclosure 2 are
possible. Preferably the part of the scraper 9 contacting the wiper
blades 6 has the shape of a wedge so that impurities are removed
from the wiper blades 6 by a sharp edge of the wedge.
Fig 1 to 3 show a system wherein the cleaning of the wiper blades 6
is done by a retraction movement of the wiper system 5 into the
enclosure 2 followed by a translation movement past the scraper 9
for removing an excess of impurities from the wiper blades 6.
A possible mechanism comprises a slit 10 provided in at least one
side of the enclosure 2 and a wiper system 5 coupled to a slider 11
for sliding in the slit 10 of the enclosure Preferably two slits 10
are provided in opposite walls of the enclosure 2 to ensure.
The slider 11 is also provided for sliding into a second slit 12
which is provided into a lever 13 for actuating the cleaning
mechanism and is coupled to a driving force 14, e.g. an electrical
motor 14 which is preferably provided externally of the service
The coupling of the lever 13 with the driving force 14 can be done
by an axis 15. A single motor 14 and axis can be provided for all
By rotation of the axis 15 induced by the driving motor 14 slider 11
is forced to follow the slit 10 in the enclosure 2. Thus the wiper
system 5 is retracted inside the enclosure 2 of the service
station 1 and translated inside the enclosure 2 whereby the wiper
blades 6 are translated past the scraper 9 thus removing accumulated
impurities from the wiper blades 6. The translation movement of the
wiper system 5 along the scraper 9 has a typical speed of
0.05-0.2 m/sec. By the enclosure 2 enclosing scraper 9 en wiper
system 5 during the cleaning operation, contamination of the
printing engine itself is avoided. Scraped of ink residues and
other impurities are collected inside the enclosure 2 of the service
station 1. Even impurities propelled away during recoil of the
elastomeric wiper blades 6 when clearing the edge of the scraper 9
can not reach the interior of the printer itself.
During the scraping operation a relative movement between the
scraper 9 and the wiper system 5 is necessary. This means that it
possible that instead of the wiper system 5 moving past the
scraper 9, it is also possible that the scraper 9 moves along the
wiper system 5 or even a combined movement of both relative to each
other will perform the cleaning of the wiper blades 6 by the
After the wiper system 5 has passed the scraper 9, the wiper
system 5 can be moved backwards along the scraper 9 cleaning the
other side of the wiper blades 6 and moving the wiper system 5 back
to the aperture 4 ready to be used again for a next wiping action of
the print head
In the described embodiment the movement of the wiper system 5
relative to the scraper 9 is a translation.
In another possible embodiment depicted in Fig. 4 to 6, the cleaning
of the wiper blades 6 is conducted in another way.
The wiper system 5 is coupled to a rotation axis 16 provided with a
gear 17 which is coupled to a second gear 18, which may be only a
segment of a complete gear, coupled to a rotation axis 15 which is
coupled to a driving force 14. In order to clean the wiper blades 6
a rotation movement of the gear segments 18 cause rotation of the
wiper system 5 to the inside of the service station 1 and at the
same time bringing the wiper blades 6 into contact with the
scraper 9 mounted inside the enclosure 2 at the opposite side of the
wiper system 5. In this embodiment the transporting of the wiper
system 5 into the enclosure 2 of the service station 1 at the same
time also provides the rotational movement for cleaning the wiper
blades 6 as can be seen in Fig. 5B. Ink residue and other
impurities are scraped off by the scraper 9 and are collected in the
enclosure 2. This cleaning can also be done in two directions,
effectively cleaning both sides of the wiper blades 6.
It is also possible to design various alternative embodiments
providing a relative movement of the wiper system 5 to the scraper 9
or cleaning system providing translation or rotational movement.
Complete separate systems can be used for retracting the wiper
unit 5 inside the enclosure 2 and for scraping the wiper blades 6
along the scraper 9. Above mentioned examples are merely possible
embodiments of the present invention. Further mechanisms for
generating the movement of the wiper blades 6 or the scraper 9 are
not described in this document because a lot of already existing
concepts are available : gear wheels, levers, motors, etc...
As already mentioned above the system has certain advantages :
- During cleaning of the wiper blades 6, no ink drops or impurities
can contaminate the surrounding area in the plotter.
- Particles (dried ink, impurities, paper dust, ...) that are scraped
of, will drop by gravity into the bottom of the inside of the
service station 1.
- Ink droplets, generated during unbending of the elastomeric wiper
blades 6 when loosing contact with the scraper 9, will be captured
by the side walls of the enclosure 2 of the service station 1.
For this the orientation of the scraper 9 and the wiper system 5
are important and have to be preferably vertical.
- As indicated above, the service station 1 contains all cleaning
elements such as the wiper system 5 and scraper. Also the capping
system (3) can be integrated into the service station (1). No
other cleaning elements are needed outside the service station 1.
By replacing the service station 1, all the impurities that were
scraped off and all involved cleaning elements are removed from
the printer or plotter. When simultaneously changing the service
station 1 upon changing a print head or changing the colour or
type of ink, no residue is left over capable of contaminating the
printer or print head.
These impurities are enclosed in the enclosure 2 of the service
station 1. So no special cleaning of the printer or plotter is
required upon changing the print head or type of ink.
Even changing of colour is thus possible without fearing
contamination of one colour with another.
- Together with the service station 1 wiper system 5, scraper 9 and
capping system (3) are replaced simultaneously. Both elements have
a limited lifetime and should be replaced periodically. Replacing
simultaneously these elements guaranties high efficiency of
In another preferred embodiment the service station 1 is provided
with means for collecting and removing residue from the service
station 1. This enables the removal of impurities during the
lifetime of the service station 1. A possible embodiment is shown
in Fig. 7 wherein at the underside of the enclosure 2 a drawer 19 is
provided for regularly removing the collected residue. If possible
the scraper 9 or alternative cleaning systems for the wiper blades 6
is mounted on the drawer which enables easy maintenance of the
The embodiment comprising a drawer 19 is preferable because it is a
relative cheap and simple system. Other system for collecting
residue can be used, even comprising moving parts such as moving
Because the cleaning of the wiper blades 6 involves generation of a
movement of the wiper system 5, either in the form of a movement
and/or rotation, a driving source 14 is necessary. This can be
provided with e.g. an internal motor inside the service station 1.
Also other driving means can be used. E.g. solenoid actuators etc...
When using a replaceable service station 1 the driving force 14 is
preferably located outside the service station 1 as shown in
Fig. 1,3,4 and 6 and the a coupling of the external driving force 14
with the internal mechanisms is provided using gears, levers, clutch
It can be seen that when exchanging a service station 1 in the
inkjet printer, the relative expensive external motor need not to be
exchanged thus making the exchangeable unit cheaper.
As can be seen in Fig. 1,3,4 and 6, it is also relatively simple to
provide a single driving force 14 or motor for several cleaning
stations serving different print heads. This is considerately
cheaper than providing separate motors.
More complicated embodiments wherein not only the wiper system 5 is
transported into the enclosure 2, but also the cleaning system
(scraper 9) is transported into the enclosure 2 before cleaning the
wiper blades 6 can be construed.
Possible embodiments include the enclosing of the wiper system 5 and
cleaning system by surrounding them by a moving enclosure.
- Parts list
Having described in detail preferred embodiments of the current
invention, it will now be apparent to those skilled in the art that
numerous modifications can be made therein without departing from
the scope of the invention as defined in the appending claims.
- service station
- capping system
- wiper system
- wiper blades
- mounting plate
- mounting hole
- slit in enclosure
- slit in lever
- driving axis
- rotation axis of wiping unit
- gear segment