Ink jet print head face cleaner

An ink jet print head face cleaner provides a controlled air passageway through an enclosure formed against the print face. Air is directed through an inlet into a cavity in a body. The body has a face with an opening into the cavity. This face is sealingly placeable against the print face. The cavity has a limited size so that air is directed without interruption through the cavity past the ink jet apertures, and out an outlet. The cleaner body is coupled resiliently to a platform to allow positioning of the body and print faces flush with each other. A vacuum source is preferably attached to the outlet to create a subatmospheric pressure in the cavity to further seal the two faces together. A collection chamber and removable drawer are positioned below the outlet to facilitate disposing of removed ink.

FIELD OF THE INVENTION 
This invention pertains to an apparatus and method for cleaning a printer 
print head, and in particular for cleaning of the aperture of an ink jet 
print head. 
BACKGROUND AND SUMMARY OF THE INVENTION 
In one basic type of ink jet head, ink drops are produced on demand. 
Exemplary drop-on-demand ink jet heads are illustrated in U.S. Pat. No. 
4,106,032 issued to Miura et al. and U.S. Pat. No. 4,727,378 issued to Le 
et al. These ink jet heads produce an ink drop at an ink-drop forming 
aperture. The ink drop is propelled through an air chamber toward a main 
external aperture of the ink jet head. Air under pressure is delivered to 
the air chamber and entrains the drop of ink in a generally coaxial air 
stream as the ink drop travels through the air chamber. 
During printing, drops of ink tend to collect in and around the ink jet 
apertures. When the ink does build up, it can prevent drop ejection, or 
cause improper ink drop trajectory and nonuniformity in ink drop size. It 
therefore becomes imperative that the aperture area be cleansed of excess 
ink periodically in order to maintain a consistently clean aperture during 
printing. 
A similar ink jet head is described in U.S. Pat. No. 4,598,303 issued to 
Peekema et al. wherein the tendency of ink to collect around the ink jet 
orifice is maintained in order to standardize drop size and trajectory. 
These types of heads are purged by flooding the air chamber with ink to 
remove contaminants and air bubbles from the ink chamber and system. The 
unwanted ink is then expelled from the air chamber into a waste reservoir 
using the air pressure system. Such purging is disclosed in the Le et al. 
patent as well as in a service manual for a color graphics copier having 
model number 4692 made by Tektronix, Inc. of Beaverton, Oreg. 
Apparatus has also been designed for cleaning the external face of the 
print head around the outer orifice. For instance physical wipers, such as 
squeegees and cloth wipes are moved across or blotted against the face. It 
is possible for such apparatus to leave some part of the cleaner substance 
in the aperture. 
One conventional external type of cleaner is described in German Patent 
Application No. DE 319704 Al based on a prior Japanese Patent Application 
No. JP P 136165/86. This cleaner provides an enlarged cavity placeable 
against the face of a print head adjacent the ink jet apertures. Gas is 
directed at the aperture with an absorbent material disposed in the cavity 
and positioned below the aperture for catching ink blown down from around 
the aperture. 
This device doesn't necessarily provide a well defined flow past the 
aperture for several reasons. Firstly, a seal is not developed between the 
cavity and the aperture face, so that the gas and ink carried by the gas 
can travel through the space between the print head and the body forming 
the cavity. Secondly, since a control volume for the impinging air stream 
from the air jet nozzle is not completely defined by solid boundaries, the 
air flow will be diverted in all directions when the air stream impinges 
upon the ink jet head. Thus, the gas flow is uncontrolled and tends to be 
dispersed. This dispersion creates inconsistency in the effectiveness of 
the fluid stream to carry the ink from the aperture. 
The present invention provides an external ink jet print head cleaner that 
maintains controlled fluid flow into the cleaning region, around an ink 
jet aperture and out of that region without contacting the aperture region 
with a solid substance. The term fluid as used herein refers to both 
liquid and gas. In particular, a continuous well-defined passageway is 
provided that directs a fluid smoothly past the aperture so that the 
pressure, mass flow and directionality of the fluid is controlled in the 
vicinity of the aperture, thereby assuring effective removal of the ink 
drops in the area of the aperture and complete removal of ink from the 
print head. 
This is provided by a body having a first face placeable against the print 
head face. This first face has an opening sized to surround the ink jet 
aperture when the first face is placed against the print head face. Means 
are provided in the body which define a cavity extending along the opening 
and having an inlet disposed adjacent to one edge of the opening. An 
outlet is disposed adjacent to a generally oppositely disposed edge of the 
opening. The cavity preferably has a depth away from the opening less than 
the length of the opening between the inlet and outlet. Finally, means are 
provided for directing a volume of a fluid through the inlet into the 
cavity and out the outlet. 
The present invention also provides a method of cleaning the aperture 
disposed in the face of an ink jet print head. This method includes 
enclosing the aperture of the print head with a cavity formed in a body 
with a first face having an opening facing the print head face, an inlet 
disposed adjacent to one edge of the opening, and an outlet disposed 
adjacent to a generally oppositely disposed edge of the opening. A fluid 
supply is directed through the inlet and cavity at an angle that is 
substantially tangential to the aperture, and out the outlet. thereby 
carrying ink disposed around the apertures out through the outlet. 
It can be seen that the present invention provides a simple, effective ink 
jet aperture cleaner. The fluid directed substantially tangentially past 
the aperture is maintained in a controlled fashion in a substantially 
unidirectional flow by a reduced cavity forming an enclosure around the 
apertures. These and other features and advantages of the present 
invention will become apparent from a reading of the following detailed 
description of the preferred embodiment in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
This preferred embodiment is intended for use with a print head with hot 
melt ink. Hot melt ink is thermally treated to melt it for deposition, 
with it then becoming solid upon cooling. Other inks such as aqueous-based 
or oil-based inks can also be used. though small changes may be required 
to handle their constant liquid state. 
Referring initially to FIGS. 1 and 2, an apparatus 10 is usable for 
cleaning a print head 12. Apparatus 10 includes a body 14 formed of a 
shell member 16 and a backing member 18. If a hot melt type of ink is 
used, these members are preferably made of a material that is rigid at the 
operating temperatures. Member 16 has what is referred to as a first 
planar face 16a in which is formed an opening 16b. This opening is sized 
to encompass the total vertical and horizontal dimensions of the array 20 
of ink jet apertures of print head 12. 
A pair of heater elements 17 and 19 are preferably mounted on the exposed 
faces of member 16 associated with face 16a, as shown, or on backing 
member 18. Elements 17 and 19 are preferably a resistive serpentine heater 
within a Kapton.TM. tape sandwich, such as the commercially available 
MINCO.TM. foil heater. Such a heater assists in preventing significant 
cooling of the print head when it is in contact with body 14. These 
heaters are only necessary if the print head is operated at temperatures 
substantially above room temperature. 
Backing member 18 has a portion 18a that is attached to corresponding back 
edges of member 16. Member 18 also comprises an insert portion 18b which 
extends inside member 16. Member 16 and member 18, in combination, form a 
passageway 22 consisting of a distribution chamber 24, inlet channel 26, 
head-cleaning cavity 28, outlet channel 30, and ink-collection chamber 32. 
The ends of the members are sealed so that there is no communication 
between sections of the passageway other than as described. 
An inlet hole 18c passes through member 18, as shown, to receive a tube 
coupling element 34 to which is attached an inlet tube 36. As illustrated, 
and as will be explained, tube 36 may be connected to a supply 38 of air 
under positive pressure relative to the ambient pressure around body 14, 
or to what is referred to as an air supply, which may simply be the 
ambient air. Although air is specifically referred to, the supply may be 
any suitable fluid, such as nitrogen gas. It is also preferable that a 
filter be placed between air source 38 and inlet channel 26. Further, if 
appropriate, it is preferable that air source 38 include a heater 39, such 
as heater coils positioned in the air path, so that the air passing 
through cavity 28 and contacting print head 12 is maintained in a heated 
condition to avoid significantly cooling the print head. 
Distribution chamber 24, inlet channel 26 and the fluid supply preferably 
provide a substantially even pressure and mass flow along the length of 
the inlet channel. 
At the upper rear portion of chamber 32 is a corresponding tube coupling 
element 40 and outlet tube 42. This tube is coupled to discharge unit 44 
that may simply be a discharge into the atmosphere, when a positive 
pressure supply 38 is used, or may be a subatmospheric pressure source, 
such as a vacuum pump. When a pump 44 is used, it also preferably 
comprises a filter for removing fine particulate matter between the outlet 
and the pump. 
Body 14 is attached to a cleaner platform 46 which comprises a floor member 
48 on which the body rests, a backing member 49 to which the body is 
attached. The body is preferably attached to platform 46 by a resilient 
connection which allows the body to move angularly relative to the 
platform. In the embodiment shown, this is provided by a connecting copper 
plate 52 having opposite ends joined to member 49 and member 18, as shown. 
The copper plate acts like a spring and allows the body to pivot about the 
plate, which runs along the length of the body. 
Platform 46 is mounted to a printer frame 54 relative to which the print 
head is positionable for cleaning, as is conventionally provided at one 
end of the travel of the print head relative to a printing zone. Platform 
46, and body 14 are movable into cleaning position by appropriate drive 
means, such as an actuator 56 mounted between frame 54 and platform 48, 
and actuator 58 between platform 48 and body 14. Face 16a is brought 
against the face of the print head for cleaning by the use of the 
actuators and spring plate 52. 
An exemplary head 12 includes a print face 12a. Head 12 includes a 
plurality of ink jets 60 distributed in array 20 along print face 12a. 
Each ink jet 60, as shown in FIG. 3, comprises an ink inlet 62, a 
piezoelectric element 64 for ejecting the ink, an ink chamber 66, and an 
ink aperture 68 out through which the ink is ejected. The outer surface of 
face 12a adjacent the apertures is preferably coated with an anti-wetting 
material 70, such as the material sold under the proprietary name 
Teflon.RTM. by DuPont Corporation. Layer 70 may be deposited to form the 
surface of face 12a as described in copending application having Ser. No. 
215,126 and entitled "Modified Ink Jet Printing Head Method for Producing 
Ink Jet Printed Images". 
The space between faces 12a and 16a is preferably as narrow as is 
reasonably possible, without the faces touching. In order to help maintain 
continuous airflow and ink flow out of cavity 28, the space between these 
faces below aperture 68 is preferably closed. This may be accomplished by 
placing a length of Kapton.TM. tape 71 along the edge 16d forming one side 
of outlet channel 30 so that it contacts face 12a during cleaning. Other 
compliant structures, such as a silicon rubber lip, could also be used. 
As shown by dashed line 72, air is directed through inlet channel 26 into 
cavity 28 toward a point upstream, or in this case, above apertures 68. 
This assures that the gas will be flowing tangentially along face 12a past 
the apertures. 
Face 16a of member 16 has a continuous groove 16c extending around opening 
16b. A resilient O-ring 74 is disposed in this groove. During operation, 
print head 12 is brought into position adjacent to cleaner 10. Cleaner 10 
is then positioned by actuator 56 with the faces 16a and 12a flush. O-ring 
74 contacts face 12a so that cavity 28 is sealed off from the ambient 
environment. The soft O-ring seal also prevents face 16a from damaging 
print head face 12a or coating 70 when apparatus 10 and print head 12 come 
in contact with each other. In the preferred mode of practicing the 
present invention as it applies to this embodiment, inlet tube 36 is 
coupled to an air source, such as filtered ambient air. Outlet tube 42 is 
coupled to a vacuum pump. 
With the vacuum pump operating, air is drawn into cavity 28 at a transverse 
angle to face 12a by inlet channel 26. The air travels tangentially and 
continuously along face 12a, past apertures 68 and out outlet channel 30. 
Any ink that has been deposited on the ink jet face outside of the 
apertures is carried down into the outlet channel. Thus, the face of the 
print head is thoroughly cleaned with a gas flow that is substantially and 
uniformly directed downwardly and away from the aperture. There are no 
impediments to the fluid path that would cause eddies or separation 
regions, which in turn could result in failure to pick up and carry away 
some ink deposits. 
The present apparatus can also be used with a positive air source attached 
to the inlet with substantially the same results. However, it has been 
found that the predominance of the subatmospheric pressure source, or 
vacuum pump, creates a stronger seal between faces 12a and 16a, which 
assures the integrity of passageway 20. 
The ink that is picked up in cavity 28 by the passing fluid flow is 
deposited in outlet chamber 32. The outlet channel is directed downwardly 
into the chamber so that the ink drips into the chamber from a lip 75 or 
is thrown against the chamber walls. The air exiting the chamber then is 
substantially clear of entrained ink. 
In order to facilitate cleanup of removed ink, a drawer 76 is placed 
through an opening 16d in the end of member 16. Drawer 76 rests on the 
bottom of chamber 32 and has sides that conform with the sides of chamber 
32. The exposed face 76a of the drawer has a handle 76b. A seal gasket 78 
is placed around drawer 76 between extended edges of face 76a and the 
associated face of member 16 around opening 16d. A latch 80 is mounted to 
member 16 for securing drawer 76 in chamber 32. Latch 80 is turned to 
allow removal of the drawer. 
Drawer 76 is preferably made of a flexible, heat resistent material, such 
as Teflon.RTM.. When the ink settles in the bottom of the drawer, it 
solidifies if it has not already done so. When the drawer is removed and 
flexed, the solidified ink is broken into pieces and dislodged from the 
drawer, thus facilitating removal. 
Cleaner 10 thus provides an effective method and apparatus for providing 
controlled fluid flow for removing residue ink from the face of an ink jet 
print head. Variations in the form and structure of the cleaner, and in 
the steps providing cleaning can be made without parting from the spirit 
and scope of the invention as defined by the claims.