Patent Publication Number: US-8523160-B2

Title: Clamp for screen printing

Description:
RELATED U.S. APPLICATIONS 
     The present application claims priority under U.S. Code Section 119(e) from a provisional patent application, U.S. Patent Application No. 61/448,903, filed on 3 Mar. 2011 and entitled “CLAMP FOR SCREEN PRINTING”. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a clamp. More particularly, the present invention relates to a clamp for screen printing. The clamp increases the service life of screen printing equipment. 
     2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98 
     Screen printing is a technique in the field of art involving ink pressed through a mesh screen onto a substrate, such as a canvas or a t-shirt. The mesh is usually woven and treated with an ink-blocking stencil so that the ink only passes through selected portions of the screen. The ink forms a pattern on the substrate as a roller, squeegee, or other scraping means pushes the ink across the screen. Screen printing is also known as silkscreen or seriography. 
     The screen includes porous woven fabric or mesh extended or a frame piece. The mesh can be made of manufactured materials, such as nylon and polyester or organic materials, such as silk. The frame is comprised of wood, metal, or other suitable material. The pattern on the screen is created by non-permeable material covering areas of the screen, similar to a stencil. The uncovered areas of the screen show the pattern, while the covered areas form a negative image of the pattern. The ink presses through these uncovered areas. There are known treatments for heat or light treatment of the screen with the stencil. 
     The ink pattern is applied to a substrate underneath the screen. As the ink is loaded onto one edge of the screen, a floodbar or scraping means moves the ink evenly across the screen so that the ink falls through the holes in the mesh only in the selected open areas of the screen. As such, the ink pattern is applied to the substrate by the slight downward force of the scraping action. Other slight variations in the process are possible, including separating the steps of filling the open areas of the mesh and contacting the substrate. In that variation, a roller or squeegee applies the downward force from mesh to substrate separate from the ink application. Multi-color patterns are possible with variations in the mesh for each color and allowing a drying time between ink applications. 
     The working life of a patterned screen can increase if used for more than one pattern. The coated material can be removed from the mesh with chemical treatment by liquids, gels, or powders. The screen must be thoroughly cleaned before re-use with a new pattern of coated material. 
     Importantly, it is common to use a coated screen multiple times. It is unlikely that there will only be a single substrate for ink application, especially considering the amount of work and effort required for the patterned coating process for the screen. The types of substrates can vary, and the screen can apply the ink pattern on a wide variety of objects, including caps, balloons, stickers, posters, etc. The number of substrates can also vary, such as several hundred t-shirts or several thousand t-shirts. In order to insure consistent placement on multiple repeated substrates, the current technology has developed a platen to be used in conjunction with the screen. The platen is a mounting board for positioning the substrate. The platen and screen engage each other so that the relative position of the platen to the screen can be maintained each time the platen and screen are connected. In this manner, consistent mounting of the substrate on the platen and consistent positioning of the platen relative to the screen insures consistent application of the ink pattern on the same location on the substrate. Various means have been used to consistently position the platen relative to the screen, including clamps attached to the screen and alignment pins. The platen technology is especially important for using multiple color applications on the same substrate. New techniques and tools for consistent ink application on each substrate continue to be developed. 
     In the past, various patents have issued relating to devices to consistently position the platen relative to the screen in screen printing. For example, U.S. Pat. No. 3,222,055, issued to Cook on Dec. 7, 1965 discloses clamps with dual threaded jaws. The jaw elements are connected by screw threads that adjust the distance between the jaws for clamping. The invention shows the flush contact of the jaws on the item to be clamped. 
     U.S. Pat. No. 4,962,918, issued to Yang on Oct. 16, 1990 teaches a clamping set having double-coordinate clamping function and being extensible for adjusting clamp depth. The clamping action occurs in more than one dimension, wherein a sliding member engages the C-clamp portion of the device. The threaded screw on the sliding member can be set perpendicular to the clamp. 
     U.S. Pat. No. 4,938,130, issued to Thorpe on Jul. 3, 1990, describes a screen printing registration device and registration method. The &#39;130 patent addresses the exact problem of consistent alignment of the platen and frame for multiple applications or re-applications. The clamp of the invention uses a pin on the platen to insure alignment of every clamped frame. 
     U.S. Pat. No. 2,642,905, issued to Hewat on Jun. 23, 1953, shows a work holding clamp with an angularly adjustable pressure element. This clamp features the usual elements, such as vertical screw threads and a clamping surface, but it also has spaces for other screws to engage the clamp at adjustable angles. This is useful for irregularly shaped projects, or ones where the project may be worked on after being positioned into the clamp. 
     U.S. Pat. No. 4,949,635, issued to Padula on Aug. 21, 1990, discloses a textile printing apparatus for multicolor printing. It contains a plurality of upper and lower arms radiating from a central hub and axle and which are rotatable with respect to one another. The lower arms have platforms for receiving textile workpieces, and the upper arms have clamping means for holding a stencil on top of a workpiece. 
     holder. 
     It is an object of the present invention to provide a clamp means for identical placement of platens relative to a frame during the screen printing process. 
     It is another object of the present invention to provide a clamp means, which increases the working life of the framed screen of the screen printing process. 
     It is an object of the present invention to provide a clamp means removably attached to the frame of a screen of the screen printing process. 
     It is another object of the present invention to provide a clamp means friction fit onto the frame of a screen of the screen printing process. 
     It is another object of the present invention to provide a clamp system, which maintains clamping force with reduced risk of mechanical failure. 
     It is an object of the present invention to provide a clamp system with reduced risk of damage to the frame of the screen. 
     It is still another object of the present invention to provide a clamp means with an adjustable alignment pin. 
     It is another object of the present invention to provide an adjustable alignment pin parallel to the jaw members of the clamp system. 
     It is still another object of the present invention to provide an adjustable alignment pin with improved resistance to deformations and/or buckling. 
     It is an object of the present invention to provide a clamp system, which is easier and lighter to transport and carry. 
     These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and claims. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention is a clamp system for use with screen printing equipment. The clamp system attaches to the frame with the mesh screen and aligns the frame with a platen, which holds the substrate. Thus, the frame and each platen are consistently aligned for repeating ink application at the same location on each substrate. The clamp system includes first and second jaw members, screws, an extension member, and a registration pin. The jaw members are aligned and have respective flat surfaces facing each other and openings aligned with each other. The screws threadedly connect the complementary openings and set the distance between jaw members for clamping action on the frame of the equipment. The flat surfaces of the jaw members abut against the frame. The extension member attaches to an end of the first jaw member and has a housing extending orthogonal to the alignment of the jaw members. The registration pin threadedly engages a hole on the housing and extends parallel to the jaw members and orthogonal to the housing. The blunt end of the pin extends from the frame and can be abutted against the platen. Each platen maintains the same position relative to the frame, whenever the blunt end contacts each platen. Thus, the registration of each platen to the frame allows for multiple consistent ink application onto the substrate. 
     The clamp system further includes the extension member made integral with the first jaw member or the extension member as an outer sheath mounted on the first jaw member. In this manner, the first and second jaw members are not interchangeable. The screws can also be replaced for other suitable connecting means between the jaw members, such as friction fit housings and ends made integral with the jaw members. Other embodiments include a system with primary and secondary clamps connected by a mounting bar. Each clamp has a respective set of first and second jaw members. The mounting bar also abuts against the frame for easier alignment of the clamps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of the clamp system of the present invention. 
         FIG. 2  is a top plan view of the embodiment of the clamp system of the present invention of  FIG. 1 . 
         FIG. 3  is a bottom plan view of another embodiment of the clamp system, showing an extension member attached to the first jaw member. 
         FIG. 4  is a side elevation view of the embodiment of the clamp system of the present invention of  FIGS. 1-2 . 
         FIG. 5  is an opposite side elevation view of the embodiment of the clamp system of the present invention of  FIGS. 1-2 . 
         FIG. 6  is a front elevation view of another embodiment of the clamp system of the present invention. 
         FIG. 7  is a back elevation view of the embodiment of the clamp system of the present invention of  FIG. 6 . 
         FIGS. 8-9  are other schematic perspective views of another embodiment of the system with primary and secondary clamps and a mounting bar between the clamps. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring to  FIGS. 1-7 , embodiments of the clamp system  10  of the present invention are accessories for use with screen printing equipment, which includes a screen, a platen, ink, a roller, and a substrate. The screen is made of a frame, usually wood, and mesh stretched across the frame. The substrate, such as a t-shirt, is set on a platen. In the prior art, mounts are drilled into the wood frame with a registration pin, so that the platen abuts against the registration pin to consistently align the substrate on the platen underneath the frame. The embodiments of the clamp system  10  of the present invention removably attach to the frame. Thus, the frame and platen are consistently aligned for repeating ink application at the same location on each substrate, and there is no permanent alteration of the frame. The embodiments of the clamp system  10  include a first jaw member  12 , a second jaw member  14 , screw means  20 ,  22 , an extension member  32 , and a registration pin  44 . 
       FIGS. 1 and 2  show the first jaw member  12  aligned end to end with the second jaw member  14 . The jaw members  12 ,  14  are not required to have identical size, but they must be aligned in a parallel relationship. The jaw members  12 ,  14  are parallel with a respective flat surface  50  of the first jaw member  12  facing a complementary flat surface  52  of the second jaw member  14 . The frame is positioned between these two flat surfaces  50 ,  52  without altering the frame. Each jaw member  12 ,  14  also has a plurality of openings  16 ,  18 , wherein the openings  16  of the first jaw member  12  are aligned with the openings  18  of the second jaw member  14 .  FIGS. 1-2  indicate that the openings  16 ,  18  can be threaded. In one embodiment,  FIGS. 1 ,  2 ,  6 , and  7 , show each jaw member  12 ,  14  being comprised of an outer casing and an inner core. In this embodiment, the openings  16 ,  18  extend through both the outer casing and inner core of the first jaw member  12 , but only through the inner core of the second jaw member  14 . Also, the openings  16 ,  18  are placed linearly along a length of each respective jaw member  12 ,  14 . Embodiments of  FIGS. 1-7  show the openings  16 ,  18  linear and parallel to edges of each respective jaw member. The embodiments of  FIGS. 1-7  show two openings as the plurality of openings  16 ,  18 , although alternate numbers of sets of openings are also possible. Any embodiment of  FIGS. 1-7  may be comprised of aluminum for the jaw members and extension members, and the jaw members and extension members may also be hollow. The reduced weight of these structures makes the clamp system more portable and lighter to carry. 
       FIG. 5  shows an embodiment with a gripping means  51  on the flat surface  50  and complementary flat surface  52  of the jaw members  12 ,  14 . The gripping means  51  can be comprised of tacky material, such as vinyl, cork, or rubber, which enables the clamp system  10  to grasp the frame with more friction force to prevent sliding between the jaw members  12 ,  14 . Any known gripping means  51 , such as coatings or other compositions can be used. Any gripping means  51  must remain flat for even contact against the frame by the jaw members  12 ,  14 . 
     The screw means  20 ,  22 , connect to the first jaw member  12  and to the second jaw member  14  in  FIGS. 1 and 2 . Each screw means  20 ,  22  connects aligned respective openings  16 ,  18  of the jaw members  12 ,  14 . The screw means  20  is located toward an end of the jaw members  12 ,  14 , to connect openings  16 ,  18 , and there is a screw means  22  further from the end for another set of openings  16 ,  18 . Embodiments of  FIGS. 1-7  show fixed ends  24 ,  26  of the screw means  20 ,  22 , respectively in the second jaw member  14 , while the other ends extend through openings  16  of the first jaw member  12 . 
     One screw means  22  comprises a locking nut  30  positioned between the jaw members  12 ,  14 , while the other screw means  20  comprises a complementary locking nut  28  on an opposite side of the first jaw member  12 . In this manner, the first jaw member  12  can be locked in place at a set distance from the second jaw member  14  by the threaded engagement of the screw means  20 ,  22  and the threaded openings  16 ,  18  of the respective jaw members  12 ,  14 . This clamping action of the screw means  22  and locking nut  30  removably fix the clamp system  10  to the frame of the screen without damage to the frame. The stabilizing action of the screw means  20  and the complementary locking nut  28  provides resistance to deformation of the clamp system  10  or warping of the jaw members. Instead of pivoting at the locking nut  30 , the first jaw member  12  remains stable by the resistance to lever action of the complementary locking nut  28 . 
     In the embodiments of  FIGS. 1-9 , the screw means  20 ,  22  are complementary. The screw means are cooperative to maintain the first jaw member  12  in a stable position. The screw means  20 ,  22  exert opposing compressive forces against the first jaw member  12  for the locked position of the jaw members  12 ,  14 . The lever action of the screw means  20  and complementary locking nut  28  maintains the tight clamping force of the screw means  22  and locking nut  30  on the frame. In alternate embodiments, the screw means  20 ,  22  can be threaded in opposite directions, and the screw means  20 ,  22  can be friction fit by screw threads, so as to maintain the jaw members at a set distance apart. There is no drilling or scratching or holes created on the frame. There is no permanent alteration of the frame in order to lock the clamp system  10  of the present invention. 
     Furthermore, one screw means can be comprised of steel, while a second screw is comprised of aluminum. In one possible embodiment, the steel screw can be the screw means  22  used for the clamping action on locking nut  30 , while an aluminum screw as the other screw means  20  can be used for the stabilizing action on the complementary locking nut  28 . Although the clamp system  10  may use the extra strength and durability of the steel screw for clamping onto the frame, the stabilizing force of the complementary locking nut  28  is not required to be as strong, since only a stabilizing force is required. The lighter aluminum material makes the system  10  lighter and easier to carry. The lever action at the complementary locking nut  28  may only be sufficient to reduce warping and deformation by the locking nut  30  and the frame. 
     The clamp system  10  of the present invention further includes an extension member  32  attached to an end  34  of the first jaw member  12 .  FIGS. 1-2  and  4 - 5  show an embodiment with an outer sheath  33 .  FIG. 3  shows an embodiment with an attached extension member  32 .  FIGS. 6-7  alternate embodiments with an integral extension member  32 ′, wherein  FIG. 6  is consistent with the embodiments of  FIGS. 1-7  and may or may not include the sheath  33 .  FIG. 7  shows a sheath  33 . 
     The end  34  of the first jaw member  12  is opposite another end  36  with the openings  16 ,  18 . At the end  34 , the attached extension member  32  further comprises a housing  38  extending orthogonal to the first jaw member  12 . There is a registration hole  40  on an end  42  of the housing  38 , which can also be threaded.  FIGS. 1 ,  2 ,  4  and  5  show the extension member  32  as a sheath  33  partially fitted over the first jaw member  12  by covering three surfaces of the end  34  of the first jaw member  12 . The remaining surface is uncovered to maintain flat contact with the frame. In this embodiment, the extension member  32  as a sheath  33  forms a groove encasing the end  34  for fixed attachment to the first jaw member  12 . Alternatively, friction fit sizing of the groove and jaw member  12  or other adhering means can be used for the sheath  33 . Including the other embodiments of FIGS.  3  and  6 - 7  without the sheath, any known prior art means can be used to adhere the extension member  32  to the jaw member  12 , including adhesives and making the extension member  32  integral with the first jaw member  12 . Depending upon materials, soldering or adhesives may be applicable. Also, in all embodiments of  FIGS. 1-7 , the extension member  32  remains flush with the flat surface  50  of the first jaw member  12 . 
     Importantly, the registration pin means  44  threadedly engages the registration hole  40  and extends parallel to the jaw members  12 ,  14  and orthogonal to the housing  38 . The registration pin means  44  has a blunt end  46 , which abuts against the platen. Similar to other systems, the registration pin means  44  insures the consistent positioning of the platen relative to the frame, and thus, the substrate. The registration pin  44  also has a threaded locking means  47 , shown in embodiments of  FIG. 2  and  FIG. 3 . The thread locking means  47  comprises a threaded screw or bolt with a hex head end and a locking nut within the housing  38 . The threaded locking means  47  adjusts the position of the registration pin  44 , while resisting any slight alterations of the registration pin  44  caused by repeated abutment of platens. The blunt end  46  may be an acorn nut or other equivalent structure which reduces the risk of damage to the platen. The repetitive knocking against the blunt end  46  by platens may slight move the registration pin  44  backward. The threaded locking means  47  can be tightly set through the registration hole  40  in order to resist these slight alterations. In embodiments of the present invention, a hand tool may be required to actuate the threaded locking means  47  for even setting the position, such that the resistance to the repetitive abutment of platens is further minimized. A hand tool can engage the hex head of the threaded bolt or screw of the threaded locking means  47  for rotation through the locking nut within the housing  38 . Additionally, in the embodiments of  FIGS. 1-9 , the housing  38  of the extension member  32  may be filled with an epoxy resin. The registration pin  44  threaded passes through the housing  38  and the epoxy resin and the threaded registration  40 . The epoxy resin provides further resistance to the wear of repeated mounting of platens on the clamped frame. 
       FIGS. 8-9  show still another embodiment of the present invention as a clamp system  310  of a primary clamp  302  and a secondary clamp  304 . The primary clamp  302  includes the analogous first jaw member  312 , a second jaw member  314 , screw means  320 ,  322 , an extension member  332 , and a registration pin  344 . The secondary clamp  304  includes the analogous first jaw member  312 ′, a second jaw member  314 ′, screw means  320 ′,  322 ′, an extension member  332 ′, and a registration pin  344 ′.  FIG. 8  shows the second jaw members  14 ,  14 ′ being connected by a mounting bar  360 , which is planar with the flat surface of second jaw members  314 ,  314 ′, extending transverse to the length of second jaw members  314 ,  314 ′ and parallel to the extension members  332 ,  332 ′. The mounting bar  360  sits atop the frame and extends through the second jaw members  314 ,  314 ′.  FIG. 9  shows the second jaw members  314 ,  314 ′ being connected by a mounting bar  362 . In this variation, the mounting bar  362  is parallel to the screw means,  322 ,  322 ′, as indicated by the arrows in  FIG. 9 . The mounting bar  362  has a flat surface orthogonal to the flat surfaces of second jaw members,  314 ,  314 ′, extending transverse to the length of second jaw members  314 ,  314 ′ and parallel to the extension members  332 ,  332 ′.  FIG. 9  shows the mounting bar  362  connecting the screw means  322 ,  322 ′ of the primary clamp  302  and the secondary clamp  304  and being flush to the edge of the frame. Thus, the two clamps can be used to position two registration pins  344 ,  344 ′ consistently and in cooperation with each other. This embodiment provides for consistent positioning of the platen and the frame using two registration pins. 
     The method of clamping with the system includes mounting a frame, tightening the jaw members, stabilizing the jaw members, and setting the registration pin. The frame is mounted between the first jaw member and the second jaw member, when the frame is placed between the flat surface of the first jaw member and the complementary flat surface of the second jaw member. Then, the jaw members are stabilized against the frame by rotating the complementary locking nut so that the complementary locking nut engages the flat surface of the first jaw member. The lever action of this complementary locking nut presses against an end of the first jaw member so as to prevent buckling and loosening by the locking nut. For the step of tightening, the locking nut on the screw means is rotated so that the flat surface of the first jaw member and the complementary flat surface of the second jaw member press against opposite sides of the frame. Once stabilized and set, the registration pin is set by rotating the registration pin through the housing of the extension member. In one embodiment, the threaded locking means is actuated by a hand tool so that the screw or bolt moves through the locking nut in the housing for a set position. For the screen printing process, a platen is aligned against the blunt end of the registration pin. The position of the platen relative to the frame is identical to a position of any subsequent platen placed against the blunt end. In an embodiment of the present invention, actuating the threaded locking means on the registration pin requires a hand tool to a set and locked position. The extra resistance of the registration pin is a feature of embodiments of the present invention, which may require setting the registration pin by manual or mechanical means. 
     The embodiments of the present invention provide a clamp accessory for screen printing equipment that maintains alignment of the platen and screen for multiple substrates. There is identical placement of the platens relative to the frame. Thus, the substrate on the platen is always positioned in the same place, so that the ink application can be consistent and precise on the substrate. Additionally, the abutment of the flat surface of the jaw members against the frame increases the working life of the frame. Unlike the prior art with drilled holes and fixed mounts, the frame has not been altered by the present invention. The clamp system of the present invention is also removable from the frame. The friction fit attachment is created by tightening screws and moving the jaw members closer and closer together, without damaging the frame. Thus, the screen can be used over and over, even when the position of the substrate is changed for a new batch of applications. 
     The embodiments of the present invention also provide a clamp system with reduced risk of mechanical failure. The screws are tightened into the jaw members instead of the frame, which prevent deformation of the clamp into the wooden frame. The screw means of the present invention provides a clamping action and a stabilizing action, unlike any prior art system. The harsh clamping action is balanced by a lighter weight lever action to keep mechanical integrity of the flat surfaces holding the frame without deformation of either structure. There is pressure exerted against the frame without any contact by screws. 
     The registration pin of the embodiments of the present invention is positioned and aligned consistently by the jaw members and extension member of the present invention. The registration pin is parallel to the jaw members and has improved resistance to deformations and/or buckling. The threaded locking means requires a hand tool because of the tightness of the threaded engagement to the registration hole, and the housing filled with epoxy resin further resists movement of the registration pin caused by repetitive contact with platens. Additionally, the clamp system of the present invention is lighter and easier to transport when made of aluminum material and when formed of hollow structures. The clamp achieves the benefits of improved working life of the screen and consistent ink application using an innovative structure. 
     The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the described system and method can be made without departing from the true spirit of the invention.