Abstract:
A frame assembly for use in supporting a silk screen. The assembly uses four corner brackets in forming the frame. The corner brackets each contain two perpendicular arms. The corner brackets engage four framing elements, thereby forming the rectangular structure of the frame. Each of the framing elements has two ends, wherein each end of a framing element receives one of the corner bracket arms. As such, each of the four corner brackets engages two of the framing elements and orients those elements at a perpendicular. An adjustment mechanism is disposed between each end of the framing elements and each of the corner brackets. The adjustment mechanism adjusts how deep an arm from a corner bracket is received within an end of a framing element. By utilizing the adjustment mechanism, the effective length of each of the sides of the frame can be selectively adjusted.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to frame assemblies that are used to support and stretch silk screens for use in a silk screen printing process. 
     2. Description of the Prior Art 
     In the many years since their invention, silk screen printing techniques have been used to print images on a wide variety of objects. Today, silk screen printing is the printing method of choice for printing on fabric such as tee shirts, sweat shirts, jackets, hats and the like. 
     In the silk screening process, a negative of an image is etched into a coated piece of silk screen. The etched silk screen is then placed upon the surface to be printed. Ink is then pressed through the silk screen. The ink passes through the silk screen in the places where the coating has been etched. The result is a positive rendition of the etched negative being reproduced in ink on the surface that was placed against the silk screen. 
     Prior to a silk screen being placed against a piece of fabric, the silk screen must be suspended in a frame so that the silk screen remains in a fixed position. Once in the frame, the silk screen must also be stretched to remove any slack in the screen that could wrinkle when the ink is pressed through the screen. Not only must a silk screen be tensioned, it must be evenly tensioned in all directions. If a silk screen is not evenly tensioned the image etched on the silk screen will be distorted and consequently the image reproduced from the silk screen will also be distorted. 
     Over the years many different types of silk screen frames have been produced. A popular type of silk screen frame uses a rectangular frame where a roller is positioned along each side of the frame. The side edges of a rectangular silk screen are connected to the rollers and the rollers are rotated to apply an even tension to the silk screen. Such prior art silk screen frames are exemplified by U.S. Pat. No. 5,937,751 to Newman, entitled, Retensionable Screen Frame And Stretchers; U.S. Pat. No. 5,802,971 to Hamu, entitled Screen Printing Frame Assembly With Screen Anchors; and U.S. Pat. No. 3,601,912 to Dubbs, entitled Woven Screen Stretching Frame. 
     A problem associated with screen frames having rollers is that it is very difficult to position a silk screen in the same location on the frame after the silk screen has been removed. As such, there are small variations that occur in the image being printed each time the same silk screen is tensioned in such a frame. 
     In an attempt to make the accurate loading and unloading of silk screens a more repeatable process, frames have been developed that do not use rollers. In such prior art frames, an adjustable slide mechanism is constructed into each frame element. The slide mechanisms typically can move about one inch within the confines of the frame. This enables each edge of the silk screen to be adjusted within the one inch range. Since the silk screen is mechanically attached to the various slides, the exact point of attachment between the silk screen and the frame can be more precisely controlled. Since the placement of the silk screen on the frame can be better controlled, the accuracy of the placement is increased. Such prior art frame assemblies are exemplified by U.S. Pat. No. 3,385,165 to Hughes, entitled Adjustable Stretch Frame For Biaxially Stressing Sheet Material. 
     A problem with all of the silk screen frames previously described is that the size of the actual frame is fixed. Silk screens come in a variety of different shapes and sizes. In the past, if a particular silk screen was too large or too small for a frame, that frame had to be replaced with one that was an appropriate size. 
     A need therefore exists for an improved silk screen frame that has a modular construction that allows the frame to be widely adjusted in size. The improved frame also requires the ability to accurately place silk screens within the frame, time after time. These needs are met by the present invention as is described and claimed below. 
     SUMMARY OF THE INVENTION 
     The present invention is a frame assembly for use in supporting a silk screen. The assembly uses four corner brackets in forming the frame. The corner brackets each contain two perpendicular arms. The corner brackets engage four framing elements, which make up the sides of the completed frame. Each of the framing elements has two ends, wherein each end of a framing element receives one of the corner bracket arms. As such, each of the four corner brackets engages two of the framing elements and orients those elements at a perpendicular. The use of four framing elements joined by four corner brackets therefore results in a rectangular or square frame. 
     An adjustment mechanism is disposed between each end of the framing elements and each of the corner brackets. The adjustment mechanism adjusts how deep an arm from a corner bracket is received within an end of a framing element. By utilizing the adjustment mechanism, the effective length of each of the sides of the frame can be selectively adjusted. Accordingly, a silk screen being mounted to the frame can be pulled taut in a highly accurate and repeatable manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a frame device in accordance with the present invention; 
     FIG. 2 is a cross-sectional view of the embodiment of FIG. 1, viewed along section line  2 — 2 ; 
     FIG. 3 is a cross-sectional view of a corner segment of the embodiment of FIG. 1, viewed along section line  3 — 3 ; and 
     FIG. 4 is a top view of the present invention showing multiple modular framing elements. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention device can be used to tension many types of materials, such as painting canvas, needlepoint backing and the like, the present invention device is particularly well suited for retaining silk screens of the type used in silk screen printing. Accordingly, an exemplary embodiment of the present invention is described below that shows the present invention used to retain a silk screen. It will be understood that this embodiment is merely exemplary and is presented only to represent the best mode contemplated for the present invention. 
     Referring to FIG. 1, a frame device  10  is shown. The frame device  10  is being used to hold and tension a silk screen  12  of the type typically used in silk screen printing. The frame device  10  has four side framing elements  14 . The side framing elements  14  are matched in set pairs, wherein the two side framing elements  14  that lay parallel to one another have the same length. However, the side framing elements  14  from adjacent sides of the frame device  10  need not have the same length. 
     The side framing elements  14  are mechanically interconnected through the use of corner brackets  16 . The structure of the corner brackets  16  is later described in detail. In forming the frame assembly  10 , the four corner brackets  16  are used. Each corner bracket  16  interconnects two adjacent side framing elements  14 . With the corner brackets  16  in place, two sides of the frame assembly  10  have an overall first length L 1  and the other two sides of the frame assembly  10  have a second overall frame length L 2 . As will be later explained, the first length L 1  and the second length L 2  of the sides of the frame device can be adjusted widely. Accordingly, a single frame assembly  10  can be used to support various silk screens  12  of widely different dimensions. 
     Referring to FIG. 2, it can be seen that each of the side framing elements  14  is tubular. Each side framing element  14  has a flat top surface  18 , an outer vertical surface  20  and a straight corner  22  which is the line of demarcation between the top surface  18  and the outer vertical surface  20 . As later will be explained, the straight corner  22  may be used as a guide when orienting a silk screen  12  within the frame assembly  10 . 
     The side framing elements  14  are slotted. Depending upon the orientation of the framing elements  14 , the slot can be positioned on either the outer vertical surface  20  of the side framing elements  14  or on the bottom of the side framing elements  14 . In FIG. 2, two side framing elements  14  are shown. One is oriented with the slot  24  on the side. The other is oriented with the slot on the bottom. 
     Regardless of the position of the slot  24 , the slot  24  communicates with the interior of the side framing element  14 . When a silk screen  12  is within the frame assembly  10 , the silk screen  12  passes over either one or two of the side surfaces of each of the side framing elements  14 . In the right hand side of the shown embodiment, the slot  24  is positioned on the outer vertical surface of the framing element  14 . As such, the silk screen  12  passes only over the top surface  18  of the framing element  14 . However, on the left hand side of the figure, the framing element  14  is oriented so that the slot  24  is disposed on the bottom of the framing element  14 . In such an orientation, the silk screen would pass over the top, the side and along the bottom of the framing element until the silk screen  12  entered the slot  24 . 
     When a silk screen  12  is first prepared, four locking rods  28  are adhered to the silk screen  12 . The four locking rods are adhered to the silk screen parallel to the four edges of the silk screen  12 . When the silk screen is being mounted in the frame device  10 , the locking rods  28  are inserted into the slots  24  of the framing elements  14 . The locking rods  28  are therefore adhered to the sections of the silk screen  12  that are looped into the slots  24  of the framing elements  14 . 
     Once the locking rods  28  are adhered to the silk screen  12 , the locking rods  28  are slid into the side framing elements  14 . The silk screen  12  extending from the locking rods  28  extends through the slot  24  in the framing elements  14 . After the locking rods  28  and the silk screen are inserted into the various side framing elements  14 , the side framing elements are attached to the corner brackets  16  (FIG. 1) and the framing elements  14  are moved apart, thereby tightening the silk screen  12 . As the silk screen  12  is made taut, the locking rods  28  are pulled against the side framing element  14 . The silk screen  12  becomes pinched between the locking rods  28  and the side(s) of the framing element  14 , thereby becoming locked into place. 
     The locking rods  28  are adhered directly to the silk screen  12 . As such, the locking rods  28  do not move in relation to the silk screen  12 . Accordingly, by aligning the locking rods  28  in the slots  24 , a silk screen  12  can be removed from the frame device  10  and repeatedly remounted in the exact same orientation. The use of the locking rods  28  therefore serves both as part of the mounting mechanism and as a mounting gauge to ensure that the silk screen  12  is mounted in the same orientation time after time. 
     Returning to FIG. 1, it can be seen that the four side framing elements  14  of the frame assembly  10  do not directly interconnect. Rather, each end of a side framing element  14  engages a corner bracket  16 . It is the corner brackets  16  that mechanically interconnect the four side framing elements  14 . 
     Referring now to FIG. 3, it can be seen that each corner bracket  16  is comprised of two slide sections  30  that are joined together at a perpendicular. In the shown embodiment, each of the slide sections  30  has an L-shaped cross-section. The slide sections  30  of the corner brackets  16  slide into the ends of adjacent side framing elements  14 , thereby joining the side framing elements  14  and orienting the side framing elements  14  at a perpendicular. 
     At the ends of each of the side framing elements  14  is positioned a threaded block  32 . The threaded block  32  defines a central aperture that is threaded. A threaded block  32  is supported in the center of each side framing element  14  near each of its ends. Spaces exist around the threaded block  32  that enable the slide sections  30  of the corner brackets  14  and the locking rod  28  to move. 
     A specialized threaded adjustment screw  34  engages the threaded block  32  at both ends of each of the side framing elements  14 . Each adjustment screw  34  has a head section  36  that abuts against an end stop wall  38  at the end of the slide section  30  of the corner bracket  14 . An engagement head  48  extends above the head section  36  of the adjustment screw  34 . The engagement head  48  extends through an aperture in the end stop wall  38 . The engagement head  48  extends-past the slide section  30  of the corner bracket  16  and provides a point by which the adjustment screw  34  can be manually rotated. In the shown embodiment, the engagement head  48  is shaped as a hex-nut that can be turned by a nut driver. In alternate embodiments, the engagement head can be slotted to receive a screwdriver or manual turn handles can be attached to each engagement head. 
     As the adjustment screws  34  are turned, the length of the adjustment screws  34  between the end stop walls  38  of the corner bracket  16  and the threaded block  32  in the side framing element  14  changes. Accordingly, the degree by which the slide section  30  of the corner bracket  16  enters the side framing element  14  also changes. As the slide sections  30  of the corner brackets  16  move in relation to the side framing elements  14 , the overall length L 1 , L 2  (FIG. 1) of the sides of the framing assembly  10  change. 
     Referring back to FIG. 1, it will now be understood that to utilize the present invention frame assembly  10 , a silk screen  12  is connected to the four side framing elements  14 . The side framing elements  14  are then attached to the four corner brackets  16 . Once the framing elements  14  are attached to the corner brackets  16 , the adjustment screws  34  at the corner brackets  16  are turned to make the frame assembly  10  longer and wider. The lengths L 1 , L 2  of each of the four sides of the frame assembly  10  can be independently adjusted. The lengths L 1 , L 2  of the sides of the frame assembly  10  are adjusted until the silk screen  12  is taut and ready for use. 
     Since the construction of the present invention frame assembly is modular, having separate side framing elements and separate corner brackets, it will be understood that the length of the various modular components can be altered to suit a specific need. Referring to FIG. 4, it can be seen that the present invention frame assembly  50  can be manufactured and sold with numerous different sets of side framing elements  52 ,  54 , each having a different length. Accordingly, the length and the width of the frame assembly  50  can be widely adjusted by using different sized side framing elements  52 ,  54 . The corner brackets  56  and the adjustment screws  58  remain constant and can be used with any of the side framing elements  52 ,  54  regardless of their size. 
     It will be understood that the various figures described above illustrate only one exemplary embodiment of the present invention. A person skilled in the art can make numerous alterations and modifications to the shown embodiment that functions in an equivalent manner to the embodiment shown and described. For example, the cross sectional shape of the corner brackets and the cross sectional shape of the side framing elements can be altered. What is important is that the corner brackets freely pass into the side framing elements and are free to move when adjusted by the adjustment screws. All such modifications are intended to be included within the scope of the present invention as defined by the appended claims.