Abstract:
A method for making a sports shaft include forming a negative image on an image-receiving surface of a flexible cover sheet, forming a first tube with a sheet of composite material, covering the first tube with the flexible cover sheet that has the negative image facing an outer surface of the first tube, and applying heat and pressure to cure the flexible cover sheet and the first tube by one or more molds to form a sports shaft having a composite core made of the composite material and the flexible cover sheet wrapped around the core and showing to the outside a positive image based on the negative image.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application 61/438,838, entitled “Structures of and methods of making sports shafts suitable for graphic application”, filed Feb. 2, 2011 by the same inventors, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to the field of sports equipment, and in particular, a sports shaft that supports a basket or a blade at its end to allow a ball or a ‘puck’ in play. 
         [0003]    Sports shafts, such as lacrosse shafts, usually include color patterns or designs on the exterior surfaces to identify the manufacturers and provide aesthetic appeal. Existing cosmetic applications include a rubberize substance, paint, or decals that lay on the surface of the shaft. These rubberized materials are typically applied by molding, shaping, extruding or hydra forming, or deep drawing on the outer surface of a pre-formed stick. For the veneer/wood covered shafts, these rubberized materials can be applied during the molding process. Graphics on the wood shaft can be applied before or after molding depending on the appearance desired for the graphics. 
         [0004]    A drawback of the conventional sports shafts is that the colors and graphic display are easily scraped off by bumping, collisions, and abrasion when the shafts are used in playing games. 
         [0005]    Some sports shafts are applied with some forms of graphics media that tend to improve grip. Such coatings, including rubber coatings, are usually not durable. Players often apply tapes around the sports shaft to improve their grips. Tapes are also often applied to other “stencil” or “silk-screened” shafts to enhance grip, as the surfaces of these sports shafts can be slippery and lack tactile feel for the players. When covered by tapes, the graphics on the sports shaft is useless in providing product identification and brand recognition as it is originally designed. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect, the present invention relates to a method for making a sports shaft that includes forming a negative image, by a printing apparatus, on an image-receiving surface of a flexible cover sheet; obtaining a first tube with a sheet of composite material; covering the first tube with the flexible cover sheet that has the negative image facing an outer surface of the first tube; and applying heat and pressure to cure the flexible cover sheet and the first tube by one or more molds to form a sports shaft having a composite core made of the composite material and the flexible cover sheet wrapped around the core and showing to the outside a positive image based on the negative image. 
         [0007]    Implementations of the system may include one or more of the following. The step of applying heat and pressure can include holding the flexible cover sheet and the first tube inside one or more molds; and applying pressure inside the first tube to press the first tube and the flexible cover sheet against the one or more molds. The method can further include inserting an elastic inflation tube into the first tube and inflating the elastic inflation tube by compressed air to press the first tube and the flexible cover sheet against the one or more molds. The step of applying heat and pressure can include heating the flexible cover sheet and the first tube to a temperature between about 180° F. to about 325° F. The negative image can be formed by a dye or an ink, wherein the method can further include before the step of forming a negative image, treating the image-receiving surface by heat, flame, the Corona process, sand blast, or a chemical to assist the adhesion of the dye or the ink to the image-receiving surface. The method can further include rolling the flexible cover sheet to form a second tube having the negative image facing inside, leaving the positive image visible from outside of the second tube, wherein the step of covering comprises inserting the first tube into the second tube. The flexible cover sheet can be formed by a material selected from the group consisting of a polymeric or a plastic material such as Nylon™, Polybutylene terephthalate (PBT), and co-extruded Nylon™ and PBT. The flexible cover sheet can be formed by a substantially transparent material. The flexible cover sheet can be formed by a translucent, a white, or substantially opaque material. The flexible cover sheet can have a thickness a range between about 0.01″ and about 0.04″. The flexible cover sheet can have a satin or matte finish on a cover surface opposing to the image-receiving surface. The negative image can be formed on the image-receiving surface of a flexible cover sheet using silk screen printing, ink jet printing or thermal dye sublimation printing. 
         [0008]    In another aspect, the present invention relates to a method for making a sports shaft. The method includes forming a negative image on a transfer sheet by a printing apparatus, forming a first tube with a sheet of composite material, covering the first tube by a flexible cover sheet, placing the transfer sheet on the flexible cover sheet with the negative image facing an outer surface of the flexible cover sheet, applying heat and pressure to the flexible cover sheet and the first tube by one or more molds to cure the flexible cover sheet and the composite material in the first tube and to transfer the negative image to the outer surface of the flexible cover sheet; and removing the transfer sheet from the flexible cover sheet to form a sports shaft having a composite core made of the composite material and a flexible cover sheet wrapping around the core. The outer surface of the flexible cover sheet can be printed with a positive image based on the negative image. 
         [0009]    Embodiments may include one or more of the following advantages. The present invention provides graphics to sports shafts with improved durability for the graphics and grips for the players, compared to the conventional sports shafts. The color printing is protected by a sheet of transparent material against abrasion and impact during the game play. The transparent material can be made of a material to improve grip and adhesion of feel of the shaft in players&#39; hands, which eliminates the need for taping over the sports shaft and allows the branding and trademarks to be visible through the use lives of the sports shafts. 
         [0010]    Another advantage of the disclosed sports shaft is that it can act as a cushion and can help dampen the feel of impact to the player&#39;s hands. 
         [0011]    Additionally, the flexible cover sheet can also protect the players from sharp edges that ensue of shaft breakage as the plastic sheet tends to stretch over a breakage and prevents the shards from injuring the player or lessons the degree of injuries. 
         [0012]    The present invention is applicable to a wide range of sports shafts such as lacrosse shafts, hockey sticks, and other shaft style tools, and various shaft cross-sectional shapes such as octagon, square, round, or oval cross sections. 
         [0013]    Although the invention has been particularly shown and described with reference to multiple embodiments, it will be understood by persons skilled in the relevant art that various changes in form and details can be made therein without departing from the spirit and scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The following drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the invention. 
           [0015]      FIG. 1  illustrates the printing of a negative image on an image-receiving surface of a flexible cover sheet. 
           [0016]      FIG. 2  illustrates the flexible cover sheet printed with a negative image on the image-receiving surface. 
           [0017]      FIG. 3  illustrates the formation of a tube by the flexible cover sheet carrying the negative image on the image-receiving surface. 
           [0018]      FIG. 4  shows that a tube-shaped of composite material is inserted inside the tube of the flexible cover sheet and the tube of the flexible cover sheet is fitted into a mold. 
           [0019]      FIG. 5  shows the formation of a sport shaft having a core made of the composite material wrapped by the flexible cover sheet showing a positive image visible from the outside. 
           [0020]      FIG. 6  shows a flowchart for forming a sports shaft in accordance with the present invention. 
           [0021]      FIG. 7  shows a flowchart for forming a sports shaft in accordance with another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    The present invention discloses a sport shaft that is covered by a flexible cover sheet that is printed with graphics such as identification, trademark, branding, and color text or images on its inner surface contacting the shaft surface. The flexible cover sheet can be molded to the shaft. The flexible cover sheet can be molded simultaneously during the molding of composite shafts, hydra-formed compressed air expansion, or other expanded molding process and forming techniques. The flexible cover sheet can also be molded to the sports shaft after the sports shaft is formed as in the case of extruded or formed alloy shafts. 
         [0023]    As shown in  FIG. 1 , a flexible cover sheet  100  includes an image-receiving surface  110 . In most cases, the flexible cover sheet  100  is formed by a substantially transparent material. In some cases, the flexible cover sheet  100  can be translucent, white, or substantially opaque. (In these cases, the colorant can diffuse deep into the flexible cover sheet  100  and still make the positive image visible from outside, as shown in  FIGS. 2-5  below). Suitable materials for the flexible cover sheet  100  can include a polymeric or a plastic material such as Nylon™, Polybutylene terephthalate (PBT), co-extruded Nylon™ and PBT, etc. The flexible cover sheet  100  can have a thickness in a range between about 0.01″ and about 0.04″, or about 0.02″ provide strength to sustain abrasion and impact during usage of the sports shaft to be formed. 
         [0024]    The image-receiving surface  110  can be treated by techniques such as heat, flame, the Corona process, sand blast, or chemicals. The treatments can alter the surface structure of the image-receiving surface  110  to make it more adhesive to the colorant to be printed, such as epoxy ink, and better adhesion to the composite material as describe below. The surface treatments can make the image-receiving surface  110  more easily adhere to the surface of the sports shafts (as shown in  FIGS. 3 and 4  below) because the flexible cover sheet  100  normally does not easily adhere to the surface of the sports shaft, such as an alloy shaft. 
         [0025]    A silk screen printing device  150  is prepared with a layer of epoxy ink in a negative image  160 , which corresponds to the intended graphics or image pattern to be displayed on the finished sports shaft. The screen printing device  150  is pressed against the image-receiving surface  110  of the flexible cover sheet  100  to print a negative image  170  of epoxy ink on the image-receiving surface  110  (step  610 ,  FIG. 6 ), as shown in  FIG. 2 . The negative image  170  can include multiple color images sequentially printed with different silk screens to render a blended color image. 
         [0026]    It should be noted that other forms of printing techniques, such as thermal sublimation printing and ink jet printing, can also be used to print the negative image  170  on the image-receiving surface  110  of the flexible cover sheet  100 . 
         [0027]    In some embodiments, a positive image can be first printed on a transfer sheet, for example, by thermal dye sublimation printing, and then transferred to form the negative image  170  on the image-receiving surface  110  of the flexible cover sheet  100  under heat and pressure. The dye molecules diffuse into the structure of the plastic to sufficient depth to become cohesive. 
         [0028]    After printing, the flexible cover sheet  100  is cut to a specified width and length which are compatible with the outer surface of the sports shaft while taking into account with the thermal expansion in the molding heat. 
         [0029]    Next, as shown in  FIG. 3 , the flexible cover sheet  100  is rolled up to form a tube  300  with the negative image  170  ( FIG. 2 ) facing inside leaving a positive image  310  visible from outside (step  620 ,  FIG. 6 ). The seam  320  of the tube  300  is held by a clear tape  330  which can be made of high-temperature resistant Mylar™. 
         [0030]    Optionally, a protective sheet (not shown) can be applied to the outer surface of the tube  300  to protect the flexible cover sheet  100  from being contaminated by resins, epoxy, or glues used during molding or assembly of the sports shaft ( FIG. 4  below). 
         [0031]    Next, referring to  FIG. 4 , a sports shaft is formed in a sports shaft molding apparatus  400 . The sports shaft molding apparatus  400  includes a lower mold  410  and a top mold (not shown for clarity purpose) which respectively have recesses  415  that together can define the shape of the sports shaft ( FIG. 5 ) to be formed. The shapes of the recesses  415  can define a cavity having a cross section in octagonal, square, round, or oval shape. The top mold and the lower mold  410  can have substantially the symmetric shape and can be heated by an external heater or furnace. The sports shaft molding apparatus  400  also includes an elastic inflation tube  420  that can be inflated by compressed air pumped into an air inlet  430  in fluid connection with the elastic inflation tube  420 . The elastic inflation tube  420  can be made of Nylon™. The air inlet  430  can be held to the elastic inflation tube  420  by a tape  435 . The top mold and the lower mold  410  also include the tube clamp  417  which can form a hole to clamp the air inlet  430  when the top mold and the lower mold  410  are held again one another. 
         [0032]    A sheet  450  of composite material is rolled up to form a tube  460  (step  630 ,  FIG. 6 ). The tube  460  is inserted inside the tube  300  formed by the flexible cover sheet  100  (step  640 ,  FIG. 6 ). The nested tubes  300  and  460  are fitted into the lower mold  410 . The elastic inflation tube  420  is inserted into the tube  460  formed by the sheet  450  of composite material. An upper mold (not shown) is then placed over the tube  300  of the flexible cover sheet  100  and clamped against the lower mold  410 , which holds the nested tubes  300 ,  460  in the cavity formed by the recesses  415  in the lower mold  410  and the upper mold (not shown) (step  650 ,  FIG. 6 ). The air inlet  430  is fit in the tube clamp  417 . The elastic inflation tube  420  is inflated to press the tube  460  of composite material and the tube  300  formed by the flexible cover sheet  100  against the lower mold  410  and the upper mold (not shown), which causes the nested tubes  300 ,  460  to expand and to conform to the shapes of the recesses  415  in the lower mold  410  and the upper mold (not shown). The lower mold  410  and the upper mold (not shown) are heated to a temperature in a range such as from about 180° F. to about 325° F. The flexible cover sheet  100  in the form of the tube  300  and the sheet  450  of composite sheet in the tube  460  are co-axially molded by heat and pressure to form a multi-layer tube assembly (step  660 ,  FIG. 6 ). After the applications of heat and pressure, the flexible cover sheet  100  and the sheet  450  of composite material are cured. The upper mold (not shown) is lifted. The ends of the nested tubes  300  and  460  are trimmed. The optional protective sheet (not shown) over the outer surface of the tube  300  is removed. 
         [0033]    As shown in  FIG. 5 , the resulting sport shaft  500  includes a hollow composite core  510  made of the composite material from the sheet  450  ( FIG. 4 ) wrapped by the flexible cover sheet  100  (step  670 ,  FIG. 6 ). The sport shaft  500  can formed in various shapes to have cross-section in octagon, square, round, oval shapes, etc. The positive image  310  is visible from outside. The flexible cover sheet  100  provides protection to the colorants (inks or dyes) that form the positive image  310  as well as the composite core  510  underneath. An advantage of the flexible cover sheet  100  is that it has sufficient thickness and strength to prevent from being abraded and scuffed from repetitive uses so the graphics and color patterns in the positive image  310  can be protected and continuously visible from outside. Another advantage of the flexible cover sheet  100  is that it can act as a cushion and can help dampen the feel of impact to the player&#39;s hands. Additionally, the flexible cover sheet can also protect the players from sharp edges that ensue of shaft breakage as the plastic sheet tends to stretch over a breakage and prevents the shards from injuring the player or lessons the degree of injuries. 
         [0034]    The texture of the flexible cover sheet can be chosen to provide additional friction and better hand grip. A satin or matte finish on the surface opposing the image receiving surface  110  can soften the appearance of the underlying graphics and dim the brilliance of the colors in the positive image  310 , which can provide desirable cosmetic effect for some users. 
         [0035]    As mentioned above, the flexible cover sheet  100  is not required to be transparent; the flexible cover sheet  100  can sometimes be formed by a translucent, a white, or substantially opaque material. In a thermal dye sublimation printing, the colorants in the negative image  170  ( FIG. 2 ) can diffuse deep into the flexible cover sheet  100  in the sublimation process such that the positive image  310  is visible from outside of the sports shaft  500  (shown in  FIG. 5 ) while being protected from resistant to scuffing and abrasions by the flexible cover sheet  100 . 
         [0036]    In some embodiments, the positive image  310  can be formed during the molding of the composite material in the composite core  510  and the flexible cover sheet  100 . A negative image is formed on a transfer sheet using, for example, thermal dye sublimation printing (step  710 ,  FIG. 7 ). A first tube is formed using a sheet of flexible cover sheet (step  720 ,  FIG. 7 ) similar to the description above in relation to  FIG. 3  except that flexible cover sheet is not printed with a negative image. A second tube is formed with a sheet of composite material (step  730 ,  FIG. 7 ) as described above. The second tube is inserted into the first tube (step  740 ,  FIG. 7 ). The transfer sheet carrying the negative image is pressed against the outer surface of the flexible cover sheet  100  (step  750 ,  FIG. 7 ), which are held in the upper mold and the lower mold with the nested tubes  300  and  460  (step  760 ,  FIG. 7 ), and applied with heat and pressure (step  770 ,  FIG. 7 ). A positive image is formed on the outer surface of the flexible cover sheet when the flexible cover sheet and the composite material are cured by the heat and pressure to form a sports shaft (step  770 ,  FIG. 7 ). The transfer sheet is removed (step  780 ,  FIG. 7 ). 
         [0037]    It should be understood that the above described methods are not limited to the specific examples used. Configurations can vary without deviating from the spirit of the invention. For example the flexible cover sheet can be formed by other types of materials than previously described. The negative or the positive images for the graphics and brand patterns can be printed with other printing techniques. The present invention is applicable to a wide range of sports shafts such as lacrosse shafts, hockey sticks, and other shaft style tools, and various shaft cross-sectional shapes such as octagon, square, round, or oval cross sections. The temperature for molding the sports shaft can vary according to the materials used.