Cover for fluid jetting device and method for enhancing fluid performance

A cover is configured for use with a fluid jet device having a surface defining a plurality of orifices formed therein through which a fluid is jetted. The cover includes a cover element movable parallel to the surface between a covered position in which the cover element overlies the orifices and an uncovered position in which the cover is moved to expose the orifices. The cover includes a mounting portion configured to maintain the cover spaced from the surface to define a vapor space region. At least one hinge element operably mounts the cover to the fluid jet device. The hinge element includes a first leg mounted at a free end to a stationary portion of the fluid jet device and a second leg mounted at a free end to the cover portion. The first and second legs are connected to one another by a flexible region such that movement of the legs slides the cover between the covered and exposed positions. The vapor space region maintains a level of fluid vapor concentration around the orifices to reduce the rate of evaporation of the fluid.

BACKGROUND OF THE INVENTION

The present invention relates to fluid jet devices. More particularly, the present invention is directed to a cover for fluid jet device heads to reduce the maintenance of the head and to improve the performance of certain jetted fluids.

Fluid jet devices are in wide-spread use. One major application of fluid jet devices is in inkjet printheads. These print heads are in wide-scale use from large industrial/commercial settings to small individual and consumer products.

Inkjet technology can be categorized as drop-on-demand and continuous jetting. In drop-on-demand printing, ink is jetted from the printhead (from a series of orifices in the head) onto a substrate. The ink is jetted or ejected as droplets in a discrete pattern to form a desired pattern, such as lettering, designs or bar codes, on the substrate. In continuous inkjet technology, ink droplets are continuously jetted and are directed, by use of a field, such as an electro-magnetic field, along a specific trajectory, to a substrate (to print) or into a gutter to be discarded.

Drop-on-demand technology can be further categorized as thermal inkjet technology, piezoelectric technology and valve-based technology. All of these technologies have certain advantages. For example, thermal technology provides high resolution with relatively low cost. Piezoelectric technology offers high jetting frequency, long lifetime, and the ability to jet a wide range of fluids.

Drop-on-demand (DOD) printing, although widely used, does have its drawbacks. For example, it is difficult to use quick-drying inks with DOD printing. These inks begin to dry rapidly, and have been found to, at times, begin drying before being ejected from the printhead orifice. This can result in the printhead orifices becoming partially or fully clogged, which can ultimately result in equipment shut downs for maintenance, repair or replacement.

Accordingly, there is a need for a device for a fluid jet device, such as a printhead, that enhances the performance of the fluid jetted from the device. Desirably, such an enhancement includes extending the life of the fluid and the usable life of the jetting device. More desirably, such a device is used in-line and has minimal or no adverse impact on the use of the jetting device.

SUMMARY OF THE INVENTION

A cover for a fluid jet device having a surface defining at least one orifice formed therein through which a fluid is jetted includes a cover element movable parallel to the surface between a covered position in which the cover element overlies the at least one orifice and an uncovered position in which the cover is moved to expose the at least one orifice. The cover includes a mounting portion configured to maintain the cover spaced from the surface to define a vapor space region. A preferred jet device includes a plurality of orifices.

At least one hinge element operably mounts the cover to the fluid jet device. The hinge element includes a first leg mounted at a free end to a stationary portion of the fluid jet device and a second leg mounted at a free end to the cover portion. The first and second legs are connected to one another by a flexible region such that movement of the legs slides the cover between the covered and exposed positions. The vapor space region maintains a level of fluid vapor concentration around the orifices to reduce the rate of evaporation of the fluid.

In one embodiment, the cover includes at least two hinge elements spaced from one another at about opposite ends of the cover element. The hinge element first leg has an extension portion that extends beyond the hinge flexible region to define a engaging portion. The cover can include fingers that depend from and extend inwardly of the cover element to maintain the cover on the faceplate and permit sliding the cover above (and parallel to) the faceplate.

A fluid jetting device especially for use with evaporative fluids includes a fluid jetting member having a faceplate defining a surface having a plurality of orifices therein through which the fluid is jetted and a movable cover for the fluid jetting member.

A method for maintaining a fluid in a fluidic or semi-fluidic state at an orifice of a fluid jetting device includes the steps of providing a fluid jet device having a plurality of orifices through which the fluid is jetted, providing a movable cover overlying the orifices, moving the cover to expose the orifices when fluid is being jetted from the orifices and moving the cover over the orifices when fluid is not being jetted from the orifices. The step of moving the cover can be effected by the movement of an object over the fluid jetting device in proximity to the cover.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures and in particular toFIG. 1, there is shown, schematically, an ink jet printing system10having a printhead12with a cover device14embodying the principles of the present invention. The printing system10includes, generally, the printhead12, an ink supply16and a waste collection system18. Lines (fluid conduits)20and valves22interconnect the various equipment items. The system10can also include a priming system24, return lines26and a vacuum system28that draws and collects vapors from the waste collection system18for automatic maintenance functions.

Generally, in operation, ink is drawn from the ink supply16by virtue of capillary action that is created at the printhead12when ink is jetted from the head12. Ink is carried by supply lines20from the supply16to the printhead12.

Waste fluid from the printhead12is routed, by a waste collection line30, from the head12to the waste collection system18. The waste collection system18includes a vapor separator32and a waste chamber34. Air and vapor from the separator32is drawn off by a vacuum pump36(which creates a negative pressure in the waste collection line30). Waste fluid can include ink that may be contaminated with dust, maintenance fluids or other non-desired materials.

The printhead12can operate by thermal, piezo-electric, valve-based or other drive principles, all of which will be well understood by those skilled in the art. In any case, the printhead12has a face plate40that is mounted to the body42of the printhead12. A plurality of jetting orifices44are formed in the faceplate40through which the ink is jetted. As set forth above, the ink can be driven using any of a number of technologies. For purposes of explanation, openings46in the faceplate40on either side of the orifices44accommodate fasteners (not shown) that secure the plate40to the body42of the printhead12.

As will be appreciated, the orifices44are small openings through which the ink is jetted or expelled. Accordingly, the orifices44can become easily clogged if debris or contaminants (such as dust) come to rest on the faceplate40. As such, waste fluid is drawn away from the plate40during maintenance operations.

It will also be appreciated that the problem of the orifices44becoming clogged is exacerbated when quick drying inks are used. Typically, quick drying inks include a solvent or carrier that is relatively volatile. This results in the liquid portion of the ink quickly evaporating after the ink has been jetted onto the object O to be printed (e.g., substrate). This also, however, can result in the liquid portion of the ink evaporating as the ink resides at the orifices44. It will be appreciated that drying occurs over a continuum. That is, as the solvent or carrier begins to evaporate from the ink, the viscosity of the ink increases to a point at which the ink becomes semi-fluidic and then subsequently becomes “dry” or solid. The present cover12is intended to maintain the ink in a fluidic or semi-fluidic, functional state for extended periods.

In order to overcome the quick evaporation of the liquid, the present cover14resides over the orifices44when the printhead12is not in the jetting mode and opens or uncovers the orifices44when the printhead12is in the jetting mode. It will be appreciated that the rate at which the carrier or solvent evaporates from around the orifices44is related to, among other factors, the concentration of the carrier or solvent in the localized atmosphere around the orifices44. If the atmosphere is “dry” or low in localized vapor concentration, the rate of evaporation increases. Conversely, when the localized atmosphere is high in carrier or solvent vapor concentration, the rate of evaporation decreases.

Accordingly, the present cover14resides over the orifices44when the printhead12is idle or not jetting and provides a localized environment E that is higher in vapor concentration than that of the surrounding environment A. The cover14is positioned over the orifices44, but is not in contact with the faceplate40at the orifice edges41. Rather, the cover14defines a gap (as indicated at48inFIG. 2B) between the inner surface50of the cover14and the faceplate40. In that the cover14extends over all or substantially all of the orifices44, the gap48provides a common or communal, localized, substantially closed environment E in which the concentration of vapors is kept at a higher level than the surrounding atmosphere A. The higher vapor concentration results in a reduced evaporation rate, which correlates to a reduced drying time and accordingly, enhanced ink (fluid) performance.

As seen in FIGS.2B and3A-H, the cover can be configured to slide parallel to the surface52of the face plate40, to expose or cover the orifices44. In a present configuration, the cover14is operably connected to the head12, for example to a portion of a maintenance module faceplate40, to move between the exposed and the covered positions. The maintenance module faceplate40can be, for example, such as that illustrated in Jackson, U.S. Pat. Nos. 6,406,125, 6,457,802 and 6,739,697, and/or Cahill, et al., U.S. Pat. Nos. 6,637,862, 6,935,721 and D477,358, all of which patents are commonly assigned with the present application and are incorporated herein by reference.

The cover14can be mounted to the printhead12by one or more living hinges54. In a present embodiment, the hinges54also serve to provide an engaging region56for contact by the object O for movement of the cover14. The hinges54include first and second rigid legs58,60joined to one another by a flexible hinge portion62. One of the legs58is mounted to the faceplate40(at about the leg free end64) and the other leg60is mounted to the cover14(at about that leg's free end66). The hinge element62is biased to draw the legs58,60toward one another. Applying a force at about the hinge portion62urges the legs58,60outward—that is to spread.

To facilitate sliding movement of the cover14, the faceplate40can include overhanging portions or flanges68(or grooves in the side of the faceplate40) and the cover14can include fingers70(that depend and extend inwardly of the cover body72) that wrap around and over the flanges68. This provides a way in which the cover14can be mounted to the faceplate40so as to maintain the vapor space or gap48for maintaining the higher vapor concentration while at the same time assuring that the cover14remains movably mounted to and spaced from the plate40. As will be appreciated from the figures, the cover12does not extend beyond the faceplate40form factor—that is, it is within the outline of the faceplate and does not extend beyond the edge43of the plate40.

As seen inFIG. 2B, with the legs58,60mounted to the faceplate40and the cover14, and the hinge54in a relaxed or contracted state, the cover14overlies the orifices44. The illustrated hinges54include an upwardly extending leg contact portion74that is an extension of the faceplate leg58beyond the hinge62. The contact portion74provides a better transition for the movement of the cover leg60.

As seen inFIGS. 3A-H, a box or other object O to be printed moves (as indicated by the arrow at76) to the printhead12, in close proximity to (e.g., a short transverse distance from) the faceplate40. As the object O moves adjacent to the printhead12(FIG. 3C), the object O contacts the contact portion74of leg58and urges the hinge62toward the faceplate40. Because the location of the free end64of the faceplate leg58is fixed, the free end66of the cover leg60moves which, in turn, forces the cover leg60to spread and the orifice cover14to open.

The contact portion74provides an accommodation for slight variations in the height or distance of the object O to be printed (e.g., the box) from the faceplate40. The contact portion74provides an extended distance range over which the object O (such as a box) can be spaced from the faceplate40and actuate the hinge54without overstressing the legs58,60. It will be appreciated that if the object O were to contact too low on the leg58, the hinge54could be overstressed, or if the object O was too high (too far from the printhead12), the cover14might not open. Accordingly, the extended contact portion74provides a greater tolerance for object O distance from the printhead12. In addition, the elongated contact surface74provides a smoother movement to the cover14as it opens. That is, the object O can “ramp up” the leg58/74to open the hinge54(and cover14).

Referring toFIG. 3D, as the object O continues to move over the printhead12and urges the hinge54toward the printhead12(downward), the cover14continues to move until fully open (FIG. 3E). Once the object O passes over the cover14and the force (of the object O) on the hinge54is removed, the hinge54begins to return to the relaxed state and the cover14begins to close ((FIGS. 3F and 3G), until the cover14is fully closed (FIG. 3H). It will be understood by those skilled in the art that this is only one way in which the cover14can be opened. It is anticipated that electro-mechanical devices, such as solenoids and the like can also be used to effect movement of the cover14. Such other arrangements and methods are within the scope and spirit of the present invention.

It will also be appreciated that the cover14provides a number of other advantages and enhancements. First, because the cover14is used in an in-line sense, that is with the printhead12in operation, it is possible to provide a means for clean “spitting”. As will be understood, “spitting” or forced purging of the printhead12is occasionally carried out to clear the printhead12. As can be imagined, without a cover14, a forced purge could otherwise result in ink being ejected into areas in which it is undesirable. The cover14provides the ability to carry out this purge without unduly spreading ink into these areas. It is also possible to shut down equipment for short periods without the need for undue purging or other extended start-up procedures.

It will be understood by those skilled in the art that the cover14provides a communal or common environment E for all of the orifices44that are “under cover”. It is the higher concentration of fluid vapors in the local environment E (relative to the surrounding atmosphere or environment A) that prevents evaporation of fluid at the orifices44and thus retards solidifying of the fluid. In that the cover14can be incorporated into the fluid jet maintenance module or faceplate40, which, in turn, is in flow communication with the waste collection system18, this provides an even greater volume for fluid/vapor interaction with the cover environment E (as through the collection line30). It is also contemplated that the cover12can be configured to provide individual compartments for each of the orifices44.

An alternate embodiment of the cover114is shown mounted to a printhead112inFIG. 4in which the cover114is actuated by electro-mechanical means, such as a solenoid115. The solenoid115can be mounted in a variety of locations and can actuated directly or indirectly (such as by a linkage, not shown). The solenoid can be actuated through the use of, for example, a proximity sensor117that is located near the printhead112that senses the presence of an object O moving toward the printhead112(as indicated by the arrow at119).

The present cover14provides a host of advantages over known printhead systems. First, it enhances the performance of the ink (fluid) jetted from the printhead12in that it retards drying and solidifying at the printhead orifices44. Such an enhancement also includes extending the life of the ink and reducing maintenance of printhead12. In addition, in that the cover is used in-line, it has minimal or no adverse impact on the use of the printhead12.

All patents referred to herein, are hereby incorporated by reference, whether or not specifically done so within the text of this disclosure.

From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover all such modifications as fall within the scope of the claims.