Abstract:
In the jet straying of ink droplets in a decorative pattern onto a fabric during which a jet spray head shuttles across the fabric changing directions at opposite selvage edges, the provision in an interposed position between the spray head and upstanding selvage edge fibers of shields preventing contact therebetween which maintains bubble closures over exit openings in the jet spray head intact and obviates inadvertent gravity flow of ink as might mar the decorative pattern.

Description:
The present invention relates generally to fabric decoration using ink jet spraying apparatus and processes and, more particularly, to accommodating the operating mode of the apparatus to the characteristics of the fabric to contribute to achieving more effective decoration of the fabric. 
     EXAMPLES OF THE PRIOR ART 
     Decorating fabric preparatory to manufacture into garments, and other end uses is achieved by dying, roller printing and, currently by the technique, now of choice which uses ink jet spraying apparatus described and illustrated in many prior patents, two such exemplary patents being U.S. Pat. No. 5,687,197 for “Ink-Jet Printing Cloth, Ink-Jet Printing Process And Production Process Of Print” issued to Aoki on Feb. 2, 1999 and U.S. Pat. No. 5,847,739 for “Cloth Feeding Drum For Ink-Jet Printing” issued to Kanaya et al. on Dec. 8, 1998. The noteworthy decorative results apparently warrant the use of jet spraying despite its intricacies, as perhaps best expressed in the &#39;739 patent at col. 1, in lines 49-52 that “In order to accurately form line and delicate patterns with ink jet printing, the distance between the ink jet nozzle and the cloth surface must be kept constant while the nozzle head is moving along the width of the cloth, and the cloth printing surface must be substantially flat.” 
     If an unsatisfactory decorative pattern is produced, the effort, even by those well versed in the art, is to seek correction in the parameters above noted, namely in adjustments in the distance between the ink jet nozzle and the cloth surface, or in the tracking of the nozzle head and so on. Even with such adjustments however, inexplicable unsatisfactory decorative results still persist, and the solution remains elusive. 
     Broadly, it is an object of the present invention to minimize unsatisfactory decorative results by not limiting corrective techniques to operating parameters of the apparatus, as is now done and is a major shortcoming of the prior art. 
     More particularly, it is an object of the present invention to achieve a synergism of the jet spraying apparatus and of the fabric being decorated which minimizes the heretofore inexplicable unsatisfactory decorative results, all as will be better understood as the description proceeds. 
     The description of the invention which follows, together with the accompany ing drawings should not be construed as limiting the invention to the example shown and described, because those skilled in the art to which this invention appertains will be able to devise other forms thereof within the ambit of the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 is a plan view of an ink jet fabric-printing apparatus; 
     FIG. 2 is a side elevational view projected from FIG. 1; 
     FIG. 3 a  is a first sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 3 b  is a second sectional view taken along line  3 — 3  of FIG. 1; and 
     FIG. 4 is an isolated perspective view on an enlarged scale of a component illustrated in FIG. 3 a.   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the drawing figures, a flat woven fabric or web  10  suitable for the manufacture of garments, upholstery and many other items is shown in whole or in part. Web  10  is conventionally manufactured to a standard width W (FIG. 1) with standard selvage edges  12  of a width S along each edge. Warp threads used in the selvage are of stronger and coarser material than those used in the balance of the web. This coarseness is the origin of the problem to be solved, all as will be better understood as the description proceeds. 
     In FIGS. 1 and 2, ink jet printing, apparatus or machinery  14  consists of a conveyance section  16  and a printing section  18 . As seen looking downstream, a direction depicted by arrow  20 , sections  16  and  18  are mounted on a right side chassis wall  22  and a left side chassis wall  24 . 
     In the conveyance section  16 , web  10  is initially put up on feed roller  26  and led past rollers  28 ,  30  and  32  all of which insure proper tracking of web  10 . At roller  32 , web  10  contacts endless belt  34  which is entrained about conveyance rollers  36  and  38 . Platen rollers  40  and  42  further insure that web  10  aligns or tracks properly in relation to print section  18 . After passing over conveyance roller  36 , web  10  passes over heater rollers  44  and  46  past heater  48  and on to take-up roller  50 . 
     The printing section  18  consists of a carriage  52  mounted on spanning rails  54  and  56 . Carriage  52  supports print head  58 . As shown in simplified form in FIG. 3 a , as below reference  60 , a supply of ink  62  is contained in housing  64  under pressure  66 . A multitude of minute orifices  68  formed by techniques known to the industry are employed to deliver a desired pattern  70  of ink droplets  72  onto the web  10 . The process of delivering each droplet  72  to web  10  utilizes the well known in the art “bubble jet system”, as described and illustrated in numerous prior patents as exemplified by U.S. Pat. No. 5,867,197 issued on Feb. 2, 1999, wherein each orifice  68  is operatively associated with an internal electro thermal converter so as to be pulsed at the appropriate time resulting in the ejection of droplet  72  onto web  10 . 
     As seen best in FIG. 1, carriage  52  is urged in movement laterally a distance F 1  after each ink ejection, N number of times to form a lateral course. At the end of each course, web  10  is advanced a distance F 2  in direction  20 . The combination of intermittent motions F 1  and F 2  results in the printing of repetitive pattern frames individually and collectively designated  74  over the surface or body of web  10 . Because of the very small size of the orifices  68  within print head  58 , a high density of droplets  72  are deposited on web  10 . Additionally, by providing multiple print heads  58  on carriage  52  the decoration of the web surface  10  can be embodied with a variety of colors and patterns  70 . 
     Referring to FIG. 3 b , where part of a typical lateral sequence is shown in elevation, print head  58  is shown in phantom line perspective at position  76  at which location it will be understood to have deposited droplets  72 , reformed bubbles  80  as closures over the orifice openings  68  and moved to position  78 . In position  78 , print head  58  continues to provide an ink droplet deposited pattern  70 , followed by reformed bubbles  80  and moves on to position  60 , and so on. 
     A problem heretofore elusive to those in the art, arises within selvage edge  12  at which upstanding fibers  82  brush against newly formed bubbles  80   a . Fibers  82  are characteristic of the previously mentioned warp threads used within selvage  12 . In the ink jet process a combination of pressure, ink viscosity and surface tension cause a bubble to form as a closure over the outlet of each orifice  68  prior to the ejection of droplets  72  on the next adjacent frame  74 . However, it is theorized that when fibers  82  snag bubbles  80   a  in position  76 , droplets  72   a  are imperfectly formed at position  78  and gravity flow of ink droplets from the orifices  58  onto the web  10  mar the decorative pattern printed on the web  10 . Stated somewhat differently, it is because the fibers  82  are not present at position  78  that bubbles  80 a are still intact when print head  58  reaches position  60 , which results in a satisfactory frame  60 . The phenomenon theorized is borne out by inspection of otherwise inexplicable unsatisfactory decorative patterns and satisfactory decorative patterns following obviating the phenomenon, as will now be described. The same problem arises when print head  58  is over the right selvage edge  12 , and similarly is solved by preventing premature bursting of the bubble  80   a  closures over the orifices  68 . 
     In FIG. 3 b , print head  58  is shown in position  76  ready to deposit a print pattern  70  on web  10 . In accordance with the present invention, a thin blade  84  is mounted in an interposed position between bubbles  80   a  and selvage  12  such that fibers  82  are shielded or restrained from contacting the bubbles  80   a . Blade  84  is mounted in cantilever fashion on bracket  86  which, in turn, is secured to wall  24  with suitable fastening means  88 . Likewise blade  84  is held in position on bracket  86  by fastening means  90 . Elongated slots  92  in bracket  86  and blade  84  allow for vertical and horizontal positioning. The overall length of blade  84  should be greater than the effective length  94  which is equivalent to frame length F 2 . The leading end  96  of blade  84  should be turned upward to avoid snagging web  10  and selvage  12 . 
     It will be understood that a similar shield  84  is provided over the right selvage edge  12  being mounted on wall  22  and, for brevity sake will not be described, being denoted by the same reference numbers. 
     From what has been described, it should be readily understood that the operating mode of the jet spraying of a decorative pattern onto the woven fabric  10  contemplates the steps of (1) urging the jet spray head  58  in alternating movements between opposite selvage edges  12  transversely across the fabric  10  on a horizontally oriented plane at a selected clearance above the fabric surface to be decorated, and (2) intermittently applying and not applying pressure on a source of ink so as to cause during a pressure application the exiting flow of ink droplets  72  through microscopic openings  68  of the jet spray head  58  onto the fabric surface  10  to be decorated. As further explained, for proper control of the exiting flow of the ink in droplets  72 , there occurs a phenomenon during a non-application of pressure of a formation of plural bubble closures  80  over the microscopic openings  68  of the jet spray head  58  as caused by fluid surface tension of the ink within the microscopic openings  68 , i.e., a surface tension that must be overcome by the next application of pressure before the ink droplet  72  can exit. 
     The problem which occurs, and which was elusive to those in the art, was the premature bursting of the bubble closures  80  upon the unavoidable contact of these bubbles by the upstanding selvage fibers  82  which, upon this happenstance, resulted in the gravity flow of the ink from the spray head  58  otherwise than in response to and in coordinated relation to applied pressure of the well known “bubble jet system” of prior patents as exemplified by the noted &#39;197 patent. Shielding the bubble closures  80  against this contact with the selvage fibers  82  by the simple expedient of providing an interposed position of a shield  84  between the spray head  58  and upper ends of the fibers  82  has resulted in practice in achieving improved jet-sprayed decoration by the obviating of a heretofore elusive source of decorative irregularities. 
     While the apparatus for practicing the within inventive method, as well as said method herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiment of the invention and that no limitations are intended to the detail of construction or design herein shown other than as defined in the appended claims.