[0001] This invention relates to a cleaning of ink jet printhead cartridges using ultrasonic
transducers in contact with a thin layer of viscous fluid.
[0002] Typically, an ink jet printer has at least one printing cartridge from which droplets
of ink are directed towards a receiver. Within the cartridge, the ink may be contained
in a plurality of channels and energy pulses are used to cause the droplets of ink
to be ejected on demand or continuously, from nozzles in a plate in an orifice structure.
[0003] In a thermal ink jet printer, the energy pulses are generally provided by a set of
electrical resistors, each located in a respective one of the channels, each one of
them is individually addressable by current pulses to instantaneously heat and form
a droplet or bubble in the channels which contact the resistors. Operation of thermal
ink jet printer is described in details in US-A-4,849,774; 4,500,895; and US-A-4,794,409.
[0004] On the other hand, a piezoelectric ink jet printing system includes a body of piezoelectric
material defining a plurality of parallel open topped channels separated by walls.
The walls have metal electrodes on opposite sides thereof to form shear mode actuators
for causing droplets to expel from the channels. An orifice plate defining the holes
through which the ink droplets are ejected is bonded to the open end of the channels.
The electrical energy pulses are applied to the parallel electrodes causing the channels
to shear actuating the expulsion of droplets from the orifice plate. Operation of
piezoelectric ink jet print heads is described in details in US-A-5,598,196; US-A-5,311,218;
and US-A-5,248,998.
[0005] Ink jet printing cartridges, whether it is of thermal or piezoelectric kind, use
a variety of functional components, all of which must cooperate in a precise manner
to achieve maximum efficiency. One of the most important components is an orifice
plate having a plurality of orifices referred to as nozzles therein. The nozzles are
usually circular in cross section and the diameter of the nozzles may vary from 10
to 100 µm as required by the specification of the printer. Higher the resolution of
the printed output, smaller is the ink droplet thereby requiring smaller diameter
nozzles. Ink is ejected through these openings during printing operation. To obtain
defect-free printing output, the orifice plates and nozzles must be kept clean and
free of debris and any kind of obstructions to ink flow at all times. If the orifice
plate and nozzles are not clean, many problems can occur thereby undermining the performance
of the printer. As for example, paper fibers and other debris accumulated on the orifice
plate surface and inside the nozzles can affect the quality of the printed images.
Similarly, debris can be dried ink crusts and paper dust on the orifice plate as well
as in the ink channels and the nozzles can cause the printer to perform poorly.
[0006] The foregoing problems are overcome, as described in US-A-5,300,958, by providing
"maintenance or service stations" within the main printer unit. The maintenance stations
are designed such that when the printhead ink cartridge is not operating and is in
a "parked" position, the cartridge is situated in the maintenance station outside
the printing zone. The maintenance stations have many components which are designed
to serve many functions. These functions include: (a) priming the printhead cartridge,
(b) capping the orifice plate and nozzles therein when the printhead is not in operation,
(c) wiping contaminants from the orifice plate, (d) preventing ink from drying out
in the openings of the orifice plate, and (e) providing a receptacle for discarding
the cleaned debris.
[0007] To accomplish this cleaning, the US-A-5,103,244 discloses a structure in which a
multi-blade wiper is used. The desired cleaning is performed by dragging a printhead
(cartridge) across the selected wiper blade. The wiper mechanism also includes a plurality
of resilient blades each having an octagonal shape and rotatable about an axis.
[0008] Another cleaning structure disclosed in US-A-5,300,958, includes a printhead wiper
unit consisting of a single or dual members positioned against each other to form
a capillary pathway therebetween. The cartridge includes a compartment having an opening
therethrough and an absorbent member impregnated with cleaning solution.
[0009] Still another cleaning structure is disclosed in US-A-5,287,126 which includes a
vacuum cleaner to help clean the orifice plate. The vacuum cleaner is comprised of
a top cover plate, having a plurality of air passages, that is located over a channel
surface by spacers. A vacuum means draws the pressure in the defined volume between
the top cover plate, the channel surface, and the spacers below the external pressure,
whereby air is drawn into the defined volume through the air passage. The resulting
air flow removes ink, dust and debris from the vicinity thereby keeping the cartridge
clean.
[0010] All the above mentioned prior arts have the following drawback: distortion of orifice
plate, wear and abrasion of the orifice plate surface and inefficient cleaning of
the printhead cartridges.
[0011] It is an object of the present invention to provide improved cleaning of ink jet
printhead cartridges.
[0012] It is another object of this invention to provide a more efficient printhead cartridge
cleaning system which not only provides a wiping unit but also permits a controlled
dislodging of debris accumulated in the nozzles and the surface of the orifice plate
and thereby cleaning the printhead cartridges.
[0013] It is another object of the present invention to provide an apparatus for cleaning
an ink jet printhead cartridge which is compact, robust and efficient.
[0014] These objects are achieved in an in ink jet printing apparatus for receiving an ink
cartridge defining an orifice structure having at least one orifice plate with a plurality
of nozzles for ejecting ink droplets onto a receiver to form an image, means for cleaning
the orifice structure of debris, comprising:
(a) at least one actuable ultrasonic transducer operatively associated with and spaced
from the nozzles;
(b) a thin layer (meniscus) of viscous fluid provided between and in contact with
the ultrasonic transducer and the orifice plate to transmit the ultrasound energy
through that fluid media;
(c) means for actuating the actuable ultrasonic transducer to cause such actuable
ultrasonic transducer to produce ultrasonic sound waves which pass through the thin
viscous fluid layer and impinge upon the orifice structure and dislodges debris; and
(d) means for wiping the orifice structure to clean it of loosened debris and the
viscous fluid.
[0015] Advantages of the invention include:
[0016] The use of a thin high viscous layer facilitates the transmission of ultrasonic sound
waves to the orifice structure which overcomes many of the disadvantages of the existing
technology, such as damages of the orifice plates and orifices due to wear, abrasion
and distortion.
[0017] Lower power consumption can be minimized because of the lower driving frequency and
effective sound wave transmission.
[0018] Cost-effective electronic integration of the actuable ultrasonic transducer to the
ink jet printhead cartridge.
[0019] Use of solvents and other undesirable chemicals can be avoided.
[0020] The actuable ultrasonic transducers can be miniaturized and easily accommodated in
a conventional maintenance station of a printer.
[0021] It is an important feature of the present invention to involve at least one actuable
ultrasonic transducer in conjunction with an ink jet cartridge and resilient wipers
for effectively cleaning the ink jet printhead cartridge of debris.
FIG. 1 is a perspective of a prior art ink jet printer depicting the prior art;
FIG. 2. is a partial isometric view of the maintenance station area of the ink jet
printer containing the actuable ultrasonic transducer of this invention;
FIG. 3 is an end view of an ink jet cartridge disposed adjacent to an actuable ultrasonic
transducer; and
FIG.4 is an enlarged partial isometric view of actuator platform.
[0022] Referring to FIG. 1, a typical ink jet printer 100 of prior art is described. Ink
jet printer 100 is of the type in which the printing is done in a substantially horizontal
plane, includes a printer housing 10, a printhead carriage 20, a carriage rod 32 (see
FIG. 2), drive roller assembly 34, paper supply 38, and maintenance station 40. Drive
roller assembly 34 feeds paper, or other print media of choice supplied to it from
the paper supply 38 to a printing zone disposed between printhead carriage 20 and
the platen (not shown) in a manner well known to artisans. Printhead carriage 20 travels
back and forth on carriage rod 32 (see FIG. 2) through the printing zone. Printhead
carriage 20 is moved bi-directionally typically by means of a drive belt 50 connected
to a carriage motor 60. Printhead carriage 20 includes ink cartridges 64 and 66 (only
two cartridges are shown here) which are connected by a flexible electrical interconnect
strip 31 to a microprocessor 24 which also controls carriage motor 60. A control panel
70 is electrically associated with microprocessor 24 for selection of various options
relating to printing operation. Such control operation and the printing mechanism
of an ink jet printer is well known in the prior art and hereby form no part of this
invention.
[0023] The present invention provides an apparatus for cleaning an ink jet printhead cartridge
which uses a high frequency actuable ultrasonic transducer in conjunction with a plurality
of conventional wipers for effectively cleaning the printhead cartridge. The actuable
ultrasonic transducers can be kept in close proximity of the cartridges intended for
cleaning in contact with a thin layer of viscous of fluid through which the sound
energy is transmitted. Ultrasonic transducers marketed by Ultran Laboratories in Boalsburg,
Pa. can be adapted to this cleaning operation.
[0024] Components of a typical ultrasonic cleaner include a generator or power supply that
converts conventional 50 Hz alternating current at 110 or 220 volts to greater than
10 MHz electrical energy at approximately 1,000 volts. This high frequency electrical
energy is fed to a converter where it is transformed to mechanical vibration. The
ultrasonic transducer has ceramic piezoelectric materials, for example, two or more
PZT (lead zirconate titanate) bodies of any convenient shape which, when subjected
to an alternating current, expand and contract. The piezoelectric bodies vibrate in
the longitudinal direction and this motion is transmitted to the transducer head.
[0025] The ultrasonic transducer is formed of materials having a high mechanical Q, thus
minimizing the attenuation experienced by the ultrasonic energy as it is transmitted
through this transducer. Q is a measure of the efficiency of the transducer. It is
defined as follows: Q=energy stored by the material/energy input. Preferably, aluminum,
titanium or an aluminum or titanium alloy having a mechanical Q greater than 50,000
is used. Examples of suitable aluminum alloys include duralumin, aluminum alloy 7075,
aluminum alloy 2024, and aluminum alloy 6061. An example of a titanium alloy which
transmits ultrasonic energy efficiently is Ti-6A1-4V. For the purpose of cleaning
ink jet printhead cartridges, the ultrasonic frequency should preferably be in the
range of between about 100 kHz and 1 MHz.
[0026] Now referring to FIG. 2, a detailed description of the maintenance station 40 of
the present invention will now be provided. The maintenance station 40 incorporates
one or more high frequency actuable ultrasonic transducers 81, 82, 83, and 84 which
transmit acoustic energy through a viscous liquid (fluid) medium. These ultrasonic
transducers are mounted on a transducer platform 80. The maintenance station 40 also
incorporates means for providing few drops of viscous fluid to provide a thin viscous
layer 81a, 82a, 83a, 84a on the transducers 81, 82, 83 and 84 respectively. The characteristics
of the viscous liquid to form a viscous meniscus are as follows:
(a) not chemically reactive such that it reacts with and contaminates the ink and
chemically degrades the orifice plate;
(b) viscosity must range from 100 to 500 centipoises;
(c) must be able to transmit ultrasound efficiently;
(d) thickness of the liquid layer (meniscus) must not exceed 1 mm and must be at least
0.1 mm; and
(e) viscous liquids that can be used are ethylene glycol, propylene glycol and glycerol,
commercially available, glycerine can be effectively used in accordance with this
invention.
Four ink jet printhead cartridges 72, 74, 76 and 78 are shown here to describe fully
the embodiment of the present invention. For purposes of the illustrative embodiment
described in this invention, cartridge 72 utilizes black ink while cartridges 74,
76, and 78 could use only cyan, yellow, and magenta ink, respectively. The cartridges
72, 74, 76 and 78 are each provided with orifice structure that can define ink channels
but will necessarily include orifice plates 72a, 74a, 76a, and 78a respectively, through
which ink droplets are ejected to a receiver. Furthermore, any number of different
colored ink cartridges could be used, as warranted by the application of the printer.
Typically, ink jet cartridges 72, 74, 76, 78 are thermal ink jet printheads, but other
kinds of cartridges, as for example, piezoelectric cartridges may also be acceptable
and useful in this invention. Each cartridge orifice structure is provided with inlets
72b, 74b, 76b, and 78b for black, cyan, yellow, and magenta inks respectively, being
delivered from reservoirs (not shown) located somewhere else. The maintenance station
40 is also equipped with resilient wipers 91, 92, 93, 94 which are mounted on a movable
wiper platform 90 for wiping off debris from the orifice structure after ultrasonic
cleaning operation of the orifice structure. The details of the operation of the wiper
is described later.
[0027] At least four wipers 91, 92, 93 and 94, as shown in FIG. 2, are provided on the movable
wiper platform 90 which is located in the maintenance station 40. An actuator 90a
provides the bi-directional translation motion of the wiper platform 90. Wipers 91,
92, 93, 94 are equipped with actuators 91a, 92a, 93a, 94a for motion in the vertical
direction. The wiper platform 90 moves slidably on two sliding rods 22 as the actuator
90a is prompted by the microprocessor 24. Alternatively, the wiper platform 90 can
also be moved bi-directionally by a motor directly connected to the platform 90a or
through a belt. Each wiper is dedicated to orifice structure of a specific cartridge.
The microprocessor 24 (see FIG. 1) controls the motion of the wipers 91, 92, 93 and
94 through the actuators 91a, 92a, 93a, 94a in such a manner that a specific wiper
engages in wiping action of a cartridge immediately after an actuable ultrasonic transducer
81, 82, 83 and 84 concludes the cleaning action of a cartridge. As for example, cartridge
72 may move across actuable ultrasonic transducer 81 for necessary cleaning action
after which is moved to wiper 91 for wiping and can be capped immediately after wiping.
The wipers 91, 92, 93 and 94 and actuable ultrasonic transducers 81, 82, 83 and 84
each are dedicated to corresponding cartridges 72, 74, 76, 78, respectively, for the
purpose of eliminating any cross contamination of debris. In other words, the actuable
ultrasonic transducers 81, 82, 83 and 84 and the actuators 90a, 91a, 92a, 93a and
94a are controlled electronically by the microprocessor 24 through a feedback circuit
(not shown).
[0028] The maintenance station 40 of FIG. 2 will be understood by those skilled in the art
to be located in a region outside the printing zone at one end of the bi-directional
movement of carriage 20. Cleaning is accomplished when the cartridges 72, 74, 76,
78 are moved by the carriage rod 32 to the maintenance station 40 where the wipers
91, 92, 93, and 94 are engaged in cleaning action.
[0029] Referring to FIG. 3, a printhead ink cartridge 72 which includes an inlet for ink
72b and orifice plate 72a is shown in close proximity to but space from an actuable
ultrasonic transducer head 81 to provide a thin high viscous layer of glycerin 81a
between the actuable transducer head 81 and the orifice plate 72a. By use of the term
"thin" is meant that the thin high viscous layer has a thickness in the range of 0.1
to 1.0 mm thick. Also shown in FIG. 3 an electrical connector 86 which can be used
for quickly connecting the actuable ultrasonic transducer 81 to a power supply 88.
[0030] Referring to FIG. 4, a detailed description of the wiper platform 90, includes the
actuator 90a for horizontal bi-directional motion of a wiper base 48 and an actuator
91a for vertical motion of the wiper 91, is given. For sake of convenience only a
single wiper 91 is shown. The wiper 91 shown in FIG. 4 has a razor like edge 43a for
effective wiping action, but other shapes can also be applicable in this invention.
The wiper 91 is mounted on a base 44 which is fastened to the actuator shaft 45. The
wiper base 48 is moved bi-directionally by the actuator 90a and the motion is controlled
by the microprocessor 24 (see FIG. 1). Other alternative means may be used to move
the platform such as a motor directly connected to the wiper base 48 or through a
belt or a lead screw (not shown).
PARTS LIST
[0031]
- 10
- printer housing
- 20
- printhead carriage
- 22
- sliding rod
- 24
- microprocessor
- 30
- wiper platform
- 31
- electrical interconnect strip
- 32
- carriage rod
- 34
- drive roller assembly
- 38
- paper supply
- 40
- maintenance station
- 43a
- wiper edge
- 44
- wiper base
- 45
- transducer shaft
- 48
- wiper base
- 50
- drive belt
- 60
- drive motor
- 64
- ink cartridge
- 66
- ink cartridge
- 70
- control panel
- 71
- ink cartridge
- 72
- black ink cartridge
- 72a
- orifice plate
- 72b
- inlet for black ink
- 73
- orifice plate
- 74
- cyan ink cartridge
- 74a
- orifice plate for cyan ink
- 74b
- inlet for cyan ink
- 76
- yellow ink cartridge
- 76a
- orifice plate for yellow ink
- 76b
- inlet for yellow ink
- 78
- magenta ink cartridge
- 78a
- orifice plate for magenta ink
- 78b
- inlet for magenta ink
- 80
- ultrasonic transducer platform
- 81
- ultrasonic transducer
- 81a
- viscous liquid (fluid) layer
- 82
- ultrasonic transducer
- 82a
- viscous liquid (fluid) layer
- 83
- ultrasonic transducer
- 83a
- viscous liquid (fluid) layer
- 84
- ultrasonic transducer
- 84a
- viscous liquid (fluid) layer
- 86
- electrical connector
- 88
- power supply
- 90
- wiper platform
- 90a
- actuator
- 91
- wiper
- 91a
- actuator
- 92
- wiper
- 92a
- actuator
- 93
- wiper
- 93a
- actuator
- 94
- wiper
- 94a
- actuator
- 100
- ink jet printer