This invention relates generally to the field of fluid jetting systems and relates, more particularly, to the means and methods used to maintain a fluid jet device of a fluid jetting system in proper working order.
An example of a fluid jet device with which this invention is concerned is a printer head of an ink jet printer. In some instances, such a printer head relies upon capillary action to move a working fluid (e.g. ink) to the printer head and includes means mounted within the head for directing ink through an orifice toward a target substrate. Such ink-directing means can include an actuator, such a piezoelectric device or an electrostatic membrane, for directing ink through an orifice upon appropriate actuation of the actuator or, in the alternative, can include a thermal device wherein heat which is applied to the ink serves as the mechanism for directing ink through an orifice.
Commonly, a fluid chamber, or ink flow passageway, is provided in the printer head which conducts ink from a source, by way of a conduit connected between the source and the printer head, and past the ink-directing means to the orifice. During normal operation of the printer head, ink must be present in the ink flow passageway so that operation of the ink-directing means effects a drawing of ink into the passageway and a subsequent pushing of ink, under pressure, through the orifice and toward a target surface. If, however, air enters the ink flow passageway through the orifice (as could be the case if the printing head were accidentally struck or jostled) or if the orifice becomes blocked, for example, by debris or dirt which may become lodged within the orifice, operation of the ink-directing means neither draws additional ink into the passageway nor does it effectively push ink through the orifice. Consequently, for effective operation of the printer head, the ink flow passageway must be devoid of air and the orifices of the printer head must remain free of blockage.
Air which is present in an ink flow passageway of a printer head and any blockage (surface or internal blockage) of the orifices of a printer head is commonly removed by a purging or head-cleaning operation which requires that additional ink be forced through the conduit and ink flow passageways by way of a purge bulb, pump or other means for forcing ink through the conduit and toward the printer head orifices. Such a purging or head-cleaning process, however, normally pushes ink, as well as air or blockage matter (e.g. debris), through the orifices so that ink which is pushed from the orifices flows downwardly along the front (i.e. the face plate) of the printer head. To prevent the ink which flows downwardly along the front of the printer head from touching or being smeared upon surfaces desired to remain free of ink, the ink is manually wiped from the front of the printing head with an absorbent sheet of material. However, such a purging and subsequent cleaning procedure requires manual intervention in and disruption of the printing operation and is usually a messy, undesirable job. Furthermore, if such a process is required to be performed on a printer head stationed along an assembly line, assembly line production may have to halted in order to satisfactorily service the printer head, thereby causing the loss of production time. It would therefore be desirable to provide a new and improved system and method for maintaining the front of a printer head in a relatively clean condition, even when ink is pushed through the orifices of the printer head during a purging or head-cleaning operation wherein air or blockage material is purged from the ink flow passageways.
Accordingly, it is an object of the present invention to provide a new and improved system and method for use when purging or cleaning a fluid chamber of a fluid jet apparatus, such as the printer head of an ink jet apparatus, for maintaining the front, or exterior surface, of the fluid jet apparatus in a relatively clean condition.
Another object of the present invention is to provide such a system and method which facilitates a purging and cleaning operation in that such operations can be performed routinely upon the fluid jet apparatus without the messiness associated with purging and cleaning operations of the prior art.
Still another object of the present invention is to provide such a system and method which circumvents the need for wiping the front, or exterior surface, of a fluid jet apparatus during a purging or cleaning operation performed upon the fluid jet apparatus.
Yet another object of the present invention is to provide such a system and method which is well-suited for automatic operation, thereby requiring no manual intervention, and can be performed without disruption of a fluid jetting operation or any assembly line operation with which the system and method are used.
A further object of the present invention is to provide a system and method which can be used to maintain an orifice of a fluid jet apparatus relatively free of blockage matter, such as debris or dirt.
A still further object of the present invention is to provide such a system which is uncomplicated in construction, yet effective in operation.
This invention resides in an apparatus and method for use when purging air or blockage from a fluid chamber of a fluid jet apparatus during a purging or cleaning operation, wherein the fluid chamber has a chamber wall with an exterior surface, an interior surface adjacent the fluid chamber, and at least one orifice through which fluid is ejected by the fluid jet apparatus during a jetting operation.
The apparatus includes a cavity adjacent the chamber wall, wherein the fluid which flows through the at least one orifice during a purging or cleaning operation flows from the at least one orifice into the cavity.
The method of the invention includes the steps of providing a cavity adjacent the exterior surface of the chamber wall into which fluid which flows from the at least one orifice during a purging or cleaning operation is permitted to flow from the at least one orifice, and withdrawing fluid which is contained within the cavity.
In another aspect of the apparatus and method, the cavity can be used to create a zone of above-atmospheric pressure in a region adjacent the exterior surface of the chamber wall so that leakage of air from said region helps to maintain the at least one orifice in a relatively clean condition. To this end, air is conducted, under pressure, to the interior of the cavity so that any leakage of air from the cavity into the atmosphere effects a flow of air out of the cavity.