Abstract:
An improved silk screen frame for tensioning a panel of screen material via the rotation of a pair of screen-tensioning members adapted to grip a flexible strip secured to the edge of the screen material in an off-center position with respect to the axis of rotation of the tensioning member. Rotation of the screen-tensioning members imparts a force which thereby stretches the screen panel material to a taut condition, and places each tensioning member in position to be engaged by a pair of adjacent rotatable finger locks which maintain the screen-tensioning members in their rotated state.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to an improved silk screen frame, and more particularly, this invention relates to a retensionable screen frame that permits the user to quickly and easily substitute one screen for another, and properly tension each screen for effective, high-quality printing. 
     BACKGROUND OF THE INVENTION 
     Serigraphy, more commonly known as screen printing, is one of the most common and versatile printing processes in use today. Screen printing can be applied to a wide variety of surfaces including paper, cardboard, glass, wood, plastic, posters, bottles, electronic circuits, etc., and to an equally wide variety of shapes. 
     The screen printing process consists generally of forcing an ink, by pressure applied via a squeegee, through the mesh of a screen stretched on a frame and onto the object to which the desired image is intended to be transferred. 
     It is generally accepted in the screen-printing trade that the quality of a printed image is directly related to the tension of the printing screen. Particularly when printing detailed designs or multicolored images, it is imperative that the printing screen be secured in a very taut condition in order to ensure that the fine details or multitude of colors are accurately transferred onto the intended object. 
     Because a particular screen pattern may be in demand for an extended period of time, the printer may desire to store the screen so that the same pattern may be reproduced at some future time without the necessity of replacing the printing screen. Historically, the difficulty with removing and replacing the stretched screen meant that the screen was stored on the frame in a stretched condition. Storing the screen in this manner not only necessitated the need for an inventory of frames, but also increased the problem associated with the deterioration of the image produced by the screen, since screens under tension tend to relax somewhat with time. 
     Moreover, because the desired image may require the use of a number of different screens, an inventory of screens is needed unless the printer can quickly and easily substitute one screen for another in the particular frame. 
     To this end, a wide variety of solutions have been formulated and are generally represented throughout the prior art as adjustable tension silk screen frames employing floating bars or tension rollers that may be adjusted in some manner to exert a greater force on the silk screen secured thereto. 
     SUMMARY OF THE INVENTION 
     Heretofore invented and disclosed herein is an improved silk screen frame for tensioning a panel of screen material and for providing a means of quickly and easily integrating a screen panel with the frame or removing the panel therefrom. 
     The improved frame of the present invention employs two rotatable members adapted to grip a longitudinal strip to which is secured the screen panel material. The rotatable members are designed to exert a rotational force on the longitudinal strips in an off-center position relative to the member&#39;s axis of rotation. Rotation of the screen tensioning members in turn imparts a force on the attached screen panel material such that the material is stretched in a taut condition for effective use in the printing process. The rotated screen tensioning members are held in their rotated position by a locking mechanism that may be engaged or disengaged with the operator&#39;s fingers. 
     Other objects, advantages, and features of the present invention will be apparent to the reader from the foregoing and the appended claims, and as the ensuing detailed description and discussion of the invention proceeds in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE VARIOUS VIEWS OF THE DRAWINGS 
     In the drawings, like reference numerals refer to like parts throughout the various views unless indicate otherwise, and wherein: 
     FIG. 1 is a perspective view of a self-tensioning silk screen frame embodying the principles of the present invention, and wherein a silk screen panel is secured to the frame and the screen tensioning members have been rotated and locked into position; 
     FIG. 2 is a perspective view illustrating the self-tensioning silk screen frame of FIG. 1 and a silkscreen panel adapted to be secured to the frame; 
     FIG. 3 is a partial, enlarged perspective view of the self-tensioning silk screen frame of FIG. 2; 
     FIG. 4 is an enlarged cross-sectional view of a portion of the self-tensioning silk screen frame taken substantially along lines  4 — 4  of FIG. 3, illustrating the rotatable screen-tensioning member and the locking mechanism in a disengaged position; and 
     FIG. 5 is an enlarged cross-sectional view like FIG. 4 illustrating an engaged screen-tensioning member and locking mechanism. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, FIG. 1 depicts a self-tensioning silk screen frame of the present invention with a tensioned silk screen panel affixed thereto generally at  10 . The assembled silk screen panel  11  (FIGS. 1 and 2) is adapted to be secured and tensioned by the self-tensioning frame  14  thereby permitting the user to quickly and easily substitute one screen panel for another in the same frame. 
     Referring now primarily to FIGS. 2 and 3, self-tensioning frame  14  is composed of a first longitudinally extending rail  36  and a second longitudinally extending rail  38  interconnected by a pair of end rails  40 ,  42  affixed at right angles thereto at each end of rails  36 ,  38 . Each end rail  40 ,  42  may be designed to secure frame  14  to a screen printing machine. 
     Self-tensioning frame  14  further comprises a pair of screen-tensioning holding members  44 ,  46  which, along with first and second longitudinally extending rails  36 ,  38 , are adapted to receive longitudinal strips  16 ,  18 ,  20  and  22  of assembled silk screen panel  11 . Screen-tensioning members  44 ,  46  are positioned perpendicular to rails  36 ,  38  and between end rails  40 ,  42  and are connected to rails  36 ,  38  via a pin  48  positioned therebetween which permits screen-tensioning members  44 ,  46  to freely rotate about axis  50  for tensioning the silk screen frame panel material  12 . Strips  20 ,  22  are herein also referred to as end members. 
     Rotatable lock members, e.g. finger locks  52 ,  54  are positioned adjacent to screen tensioning members  44 ,  46  along second longitudinally extending rail  38  such that they may be rotated into a position to engage the respective screen-tensioning member and thereby lock said screen-tensioning member into a position wherein the silk screen panel material  12  is stretched to a taut condition. 
     A variety of fabric types are available for use in the screen panel  12 , each of which will create a different overall impression of the particular print. Organdy and silk are the two most basic fabrics and were traditionally used in this form of printing. Monofilament nylon fabric and polyester are stronger and have replaced the traditional “silk” screen for many contemporary applications of this printing process. In addition, screens made from stainless steel and nickel-plated polyester may be used to achieve a grainier texture in the ink, but are more easily ripped or creased than are the nylon or polyester screens. 
     The screen panel  11  may be obtained in a pre-assembled form with four longitudinal strips  16 ,  18 ,  20 , and  22  affixed to the edges of the screen material and adapted for use in the self-tensioning frame  14 , or the user may assemble the screen panel individually. 
     Each longitudinal strip is composed of a three-sided channel member  24 , and a block  32  which is adapted to be received in channel member  24  and thereby secure an edge of the silk screen panel  12  to the particular longitudinal strip with which it is associated. The bottom side  26  of channel member  24  extends a particular length beyond a first vertical side  28  of channel member  24  to form extension  34 , while remaining flush with a second vertical side  30  (see FIGS.  4  and  5 ). This configuration is designed to securely fit within the first and second longitudinally extending rails  36 ,  38  and screen-tensioning members  44 ,  46  as illustrated in FIGS. 4 and 5. 
     Having observed the details of the various components of the self-tensioning frame and the adapted silk screen panel assembly, attention may now be given to the placement of the screen panel  11  into the self-tensioning frame  14 , and the tensioning of the silk screen panel material  12 . 
     Referring now primarily to FIGS. 2,  4 , and  5 , the assembled silk screen panel  11  may be connected to the self-tensioning frame  14  by first inserting either one of side longitudinal strips  16 ,  18  into the corresponding first or second longitudinally extending rail  36 ,  38 . Extension  34  is inserted first while the user holds the particular longitudinal strip at an angle. After having placed a first longitudinal strip into an associated longitudinally extending rail, the user then inserts the other strip in the same manner beginning at one end of the corresponding rail and moving toward the opposite end. The longitudinal strips are flexible and will bend as pressure is applied to them so that they may be snapped into place. 
     The next step in connecting the assemble silk screen panel  11  to frame  14  is similar to that just described, except that screen-tensioning members  44 ,  46  may be rotated in a direction toward screen panel  11  (opposite from the tensioning direction illustrated by arrow  56  in FIG. 4) in order to more easily insert the corresponding longitudinal strips or end members  20 ,  22 . With these strips in position, screen-tensioning members  44 ,  46  are then rotated downwardly as indicated by the arrow referenced as numeral  56  in FIG.  4 . The off-center position of the pin  48  (illustrated by broken lines in FIGS.  4  and  5 ), about which each screen-tensioning member rotates, provides increased leverage for tensioning the silk screen panel material  12 . 
     Each screen-tensioning member is rotated to a position, as illustrated in FIG. 5, whereby the corresponding finger lock  52 , or  54  can be rotated in an upwardly direction, as indicated by the arrow referenced as numeral  58  in FIG. 4, to engage the screen-tensioning member and thereby hold said member in a tensioned position so that the silk screen panel material  12  remains taut. 
     Removal of the assembled screen panel  11  from the self-tensioning frame  14  is effected by disengaging the finger locks  52 ,  54  from screen-tensioning members  44 ,  46 , rotating said members in an upwardly direction opposite that of arrow  56  (see FIG.  4 ), and removing longitudinal strips  20 ,  22  therefrom. Finally, either longitudinal strip  16 , or  18  may be removed by pushing the strip out of its rail via a specially adapted push tool (not shown) or similar instrument or device which is capable of being inserted through one of a plurality of small holes machined into the underside of each longitudinally extending rail  36 ,  38 . Once one side longitudinal strip has been removed, the other can be easily slipped out of its position. 
     While the invention is described and illustrated here in the context of a particular embodiment, the invention may be embodied in many forms without departing from the spirit or essential characteristics of the invention. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.