Abstract:
A device is provided for holding down textile material (on which images or text are to be printed) on the platen of a digital printing machine. The device includes facing flexible rubber pads or seals mounted on the periphery of the platen. The seals have opposed gripping surfaces which touch or have a selected limited spacing there between. The textile material is pushed and tucked in between the seals. The seals grip and hold the material in position, to provide a smooth material surface on which the ink is applied. After the printing operation, the textile material is pulled out from the seal grip.

Description:
This patent application is based on, and claims the priority date of, U.S. provisional patent application Ser. No. 60/879,144 filed on Jan. 6, 2007, having the same title as this application and filed by John C. Livingston, the same inventor named herein. 
    
    
     BACKGROUND OF INVENTION 
     The present invention relates to the relatively recent development and commercial exploitation of digital printing techniques in which a full size printer prints on textiles directly. For several reasons, the aforesaid method is an improvement over the long used and standard screen printing methods. The digital printing method makes possible the reproduction of complicated design, to print colors that were not feasible before, to readily make changes in design etc. More recently, improvements on digital printers have enabled printers to print on different type materials and on material of different sizes and on material mounted on relatively large platen bases. One of the problems in placing the materials on the platen is that the material must be wrinkle free, and be stretched tautly and smoothly over the platen. Since the platens and the material mounted thereon were both relatively of big size, better means have been sought for mounting the material on the platen in a smooth, wrinkle free and firmly taut fashion. 
     SUMMARY OF INVENTION 
     The present invention relates to a digital printer for textile material wherein an improved device is provided for holding down the textile material on the platen of a printing machine. The textile is held down in a smooth, firm and wrinkle free position for purposes of suitably printing images and/or text thereon. The inventive device includes spaced facing extruded rubber seals comprising gripping seals mounted on the sides of the platen. The seals have opposed gripping surfaces with a limited spacing there between. The material is pushed and tucked into the limited space. The seals grip and hold the material, in position throughout the periphery of the platen, to provide a smooth material surface on which the ink is applied. After the printing operation is completed, the material is pulled out from the grip of the seals. 
     The foregoing features and advantages of the present invention will be apparent from the following more particular description of the invention. The accompanying drawings, listed herein below, are useful in explaining the invention. 
    
    
     
       DRAWINGS 
         FIG. 1  depicts a textile digital printing machine of the type on which the Hold Down Device of the invention is mounted and further depicts a T-Shirt mounted on the movable platen preparatory to insertion into the printing unit of the machine; 
         FIG. 2  is an exploded view of the gripping device of the invention showing the gripping seals mounted on the periphery of the platen; 
         FIG. 2  is an exploded view of two rubber gripping seals indicating the mounting of the seals within a rigid C-shaped elongated flange; 
         FIG. 4  is a cross section view of the seals showing the gripping surfaces of the seals; 
         FIG. 5A  depicts the textile material being forced into the limited space between the gripping seals by the operator&#39;s finger; 
         FIG. 5B  indicates a rod or blade or roller that can alternatively and conveniently be used to force the textile into the space between the seals; 
         FIG. 6  shows the textile material in a gripped position between the reformed or compressed seals to provide the gripping action; 
         FIG. 7  shows a flange with adjustable sides for adjusting the spacing of the seals for compensating for textiles of different texture and/or thickness; and 
         FIG. 8  shows spring clamps that are useful in adjusting the positioning and tension of the gripping seals to accommodate seals of differing materials. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a digital textile printing machine  11 , of suitable known type, wherein a textile material to be printed on, herein indicated as a T-shirt  15 , is placed on (draped over) a platen  14 . Platen  14  is commonly rectangular in shape. In preparation for the printing procedure, the T-shirt  15  is removably held on the platen  14 . The platen  14  can then be moved (slid) into the printing portion of the machine  11  for positioning the textile material under the print head, as is well known. Importantly, it is necessary that the material on which an image or text is to be printed be smooth and wrinkle free to obtain a clear and blur free text and/or images. 
     Refer now also to  FIGS. 2 and 3 . For the purpose of mounting the textile material on the platen  14  as required, gripping pads or seals  20  and  21 , made of flexible material such as rubber formed in tubular cross section, are positioned on the periphery of the platen  14 , as indicated in  FIG. 2 .  FIG. 3  shows that the gripping pads or seals generally labeled  20  and  21  respectively comprise four sections for the four sides of the rectangular platen  14  and are mounted on respective C-shaped flanges or channels generally labeled  22 . Flanges  22  are, in turn, suitably mounted on the periphery of the platen  14 , as indicated in  FIGS. 2 and 4 . The C-shaped flanges  22  are positioned to have to the opening of the C-shape facing outwardly relative to the platen  14 . 
     The first seal, generally labeled  20 , and the second seal, generally labeled  21 , are positioned in a facing or fronting elongated relation adjacent each other, and in the respective flanges  22  as indicated in  FIGS. 2-4 . Either one or both seals may have ribs, teeth or protrusions  23  on the periphery thereof to assist in holding the textile material. See for example, seals  20 A and  21  in  FIG. 4  and seals  20  and  21  in  FIG. 5A . In one embodiment the seals are mounted to have a spacing of one thirty second of an inch ( 1/32) between their facing surfaces. The spacing is dependent on the type and thickness of the material being printed upon. For very thin or slippery material such as rayon or silk the seals may be mounted in a position touching one another. 
     As mentioned above with reference to  FIG. 2 , there are four sections of gripping seals or pads  20  and  21 , and each section of seals  20  and  21  mounted in a respective flange  22 . One section of seals and the associated flange is mounted on each side of the platen  14 s, one section of seals and the associated flanges are mounted the front, and other section of seals is mounted on the rear end of the platen. For purposes of clarity in the drawing of  FIG. 2 , only the flange  22  on one side of the platen is depicted; the other flanges are omitted to permit an unobstructed view of the positioning of the four sections of the gripping seals  20  and  21 . Note that each section of seals includes the two facing seals  20  and  21 . 
     In one embodiment, the seals are of foam rubber having a thirty durometer hardness. Dependent on the textile being printed, various types of flexible material may be used for the seals. In a preferred embodiment, both seals are of foam rubber, however in other embodiments one seal may be of a compressible (yielding) material and the other seal could be of a relatively non-compressing material, such as rigid plastic. 
     Refer now also to  FIG. 5A  which depicts a preferred method of inserting a textile  15  to be gripped by the seals  20  and  21  which form a snug but flexible gripping device. As mentioned above, in one embodiment the seals  20  comprises elongated tubular members having a smooth surface that contacts the textile, and seals  21  comprises elongated tubular members having ribs that contact the textile. The seals may also comprise essentially identical units both having ribs on their textile engaging surface, as depicted by seals  20 A and  21  in  FIG. 4 . 
     Seals  20  and  21  comprise elongated tubular bodies of a foam rubber material that is compressible and the seals are positioned in flanges  22  fronting or facing each other. The seals may be in touching relation to each other, or mounted to have a limited spacing there between. The spacing between the seals is determined to accommodate the particular thickness of material which is to be printed. The textile  15  is placed over the platen  14  in a position to extend and drape over the seals  20  and  21 . Using finger pressure the textile  15  is tucked (pushed) into the limited space between the seals  20  and  21 . 
     As shown in  FIG. 6 , the seals  20  and  21  are compressed to engage and hold the textile  15  in position. This tucking or pushing in of the textile material is done around the periphery of the platen  14 , as needed. Dependent on the material, the front and back ends of the material may not have to be tucked in. The platen  14  and textile  15  are then moved into printing position in machine  11 . After the digital printing is done, the platen  14  is withdrawn from the machine  11  and the textile  15  is pulled out of engagement between the seals  20  and  21 . 
       FIG. 5B  shows a rod or blade  26  that may be conveniently used, instead of the operator&#39;s finger, to tuck in the textile material  15  between the seals. 
       FIG. 7  depicts that in another embodiment showing that the C-shaped flange  22  may be made in essentially two elongated L-shaped halves  22 A and  22 B that may be attached to each other by suitable bolts or screws  27  for adjusting the size of the cross section of the flange  22  to accommodate seals  20  and  21  of varying diameters, and/or to adjust the gripping force of the seals  20  and  21  mounted in the flange. 
       FIG. 8  shows that the flange halves  22 A and  22 B can be spring loaded as at  29  to further provide additional horizontal adjustment of the positioning of the seals  20  and  21  mounted in the flanges  22 A and  22 B. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.