Patent Publication Number: US-2022234343-A1

Title: Rubber product with a printed surface and method for forming a printed surface on the same

Description:
TECHNICAL FIELD 
     The present invention is related to a rubber product with a printed surface and a method for forming a printed surface on the rubber product, rendering the printed surface of the rubber product more resistant against abrasion and corrosion. 
     BACKGROUND 
     Conventional rubber products or key buttons normally take the form of a casing sheathed by a rubber layer around the casing. Such rubber layer is mainly applied to the conventional rubber products or key buttons that are adopted in televisions or electronic products but are not limited thereto and only serves to shed light on the scope of applications for key buttons in the present invention. Basically, the resilient nature of the rubber layer makes itself not a perfect material to be printed unless it undergoes a sulfurization process arising from a heating and pressing process. Despite higher degree of resilience, the crosslinking reaction in the sulfurization process also hardens the surface of the rubber layer to result in a fixed form required for printing. Also because of the increased temperature and pressure in the sulfurization process, the rubber layer is usually carried out a form pressing while it is heated. In other words, the rubber layer is placed between a male (lower) die and a female (upper) die to be stamped to a designated form before moving on to subsequent printing operation simply because all protruded areas have their intended forms for most of the key buttons after the pressing and then facilitate the printing operation, which is the conventional 2-dimensional screen printing, on their surface. In the event of special demand, background color can be done by spray painting first before a baking process. If needed, a second baking process is performed after the printing or even numerous printing and baking processes may be involved. It is known that the rubber layer should have a fixed form before color printing on its surface. As the rubber layer gets deformed and hardened after several rounds of baking process, most of conventional printing methods employ single-color printing to ensure the yield of finished products. For sake of one baking process for one color printed on a product, the size of the product varies with many baking processes because the size is changed by evaporation of organic materials in each baking process. Such size variation is proportional to the number of baking process and causes a lower yield of the product accordingly. Consequently, the printing operation can only be manually conducted in a piece-by-piece fashion, which in turns leads to a higher production cost and impacts automation of overall production process. 
     Furthermore, as disclosed in Chinese Utility Model No. CNS2459162Y, a method transfer-printing a pattern on a rubber product includes printing the pattern on a transfer paper in advance, simultaneously placing a natural rubber material and the transfer paper into a die assembly, pressing the natural rubber material through a sulfurization process at high temperature and pressure, and transfer-printing the pattern on the transfer paper onto the rubber product in the course of the press-forming. Such method transfer-printing the pattern on the transfer paper relies on adhesive on the transfer paper for the transfer paper to be directly attached to the rubber product at high temperature and pressure. However, when being subject to high temperature and pressure in the die assembly, the transfer paper is prone to retraction, which further deforms the pattern on the transfer paper. Moreover, as being also stuck on the rubber product with the adhesive, the pattern on the transfer paper may easily come off when it is rubbed and can be worn out easily if the rubber product is used in a frequent manner. 
     In view of the foregoing disadvantages of the conventional rubber products, how to provide a printed layer on the surface on a rubber product with more abrasion resistance and a printing method in fulfillment of production automation becomes a substantial issue to be tackled. 
     SUMMARY 
     An objective of the present invention is to provide a rubber product with a printed surface and a method for forming the printed surface on the rubber product for a printed surface layer of the rubber product to have better resistance against abrasion and corrosion. 
     To achieve the foregoing objective, the rubber product with a printed surface includes a base and a printed surface layer. 
     The base is made of a natural rubber material undergoing a sulfurization process. 
     The printed surface layer has the printed surface on the base and formed by ink made of the natural rubber material and is fused with the base after the printed surface layer and the base are heated and pressed. 
     Preferably, the printed surface layer has at least one color formed thereon. 
     Preferably, the printed surface layer has at least one key button region or at least one label region formed thereon. 
     Preferably, the printed surface layer is printed by way of multi-layer printing. 
     To achieve the foregoing objective, the method for forming a printed surface on a rubber product includes: 
     a pre-printing step forming a printed surface layer on each of at least one plate heated and pre-shrunk beforehand, in which the printed surface layer on each of the at least one plate is printed on the plate with inks containing a natural rubber material; 
     a pre-shrinking step heating the at least one plate for the printed surface layer on each of the at least one plate to be shrunk to a designated form; 
     a fusing step simultaneously placing the at least one plate and a substrate made of the natural rubber material into a die assembly with the printed surface layer on each of the at least one plate adjacent to the substrate, heating and pressing the at least one plate and the substrate inside the die assembly at the same time for the substrate to form a base through a sulfurization process, and fusing adjacent surfaces of the base and the printed surface layer on each of the at least one plate together during the sulfurization process to form a preliminary workpiece; and 
     a cutting step cutting the preliminary workpiece into a predetermined shape to form the rubber product with the at least one printed surface layer. 
     Preferably, the at least one plate is made of a material that has a melting point higher than that of the natural rubber material and is selected from one of PC (Polycarbonate), TPU (Thermoplastic Polyurethane), PET (Polyethylene Terephthalate). 
     Preferably, in the pre-printing step, each of the at least one printed surface layer having at least one pattern is formed on one of the at least one plate and each of the at least one pattern is printed with multiple colors. 
     Preferably, in the cutting step, the preliminary workpiece is cut when the preliminary workpiece is inside or removed from the die assembly. 
     Preferably, the method further includes a separating step removing the at least one plate from the at least one printed surface layer respectively after the preliminary workpiece is formed. 
     Preferably, the at least one plate includes one plate with one printed surface layer formed on the plate. 
     Preferably, the at least one plate includes two plates with two printed surface layers formed on the respective plates and the two printed surface layers are arranged to be adjacent to two opposite sides of the substrate in the fusing step. 
     In contrast to conventional techniques, the rubber product formed by the present invention has the following advantages: 
     Because both the printed surface layer and the base contain the natural rubber material, the natural rubber material allows the printed surface layer and the base to be fused together due to fused connection out of the sulfurization process, thereby not only increasing the capability against abrasion but providing better resistance against corrosion and more decent waterproof effect for the printed surface layer. 
     Besides single-sided printing, two plates with two printed surface layers formed thereon respectively can be arranged on two opposite sides of the substrate made of the natural rubber material to further achieve double-sided printing on the substrate at the same time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
         FIG. 1  is a 3D schematic diagram showing a rubber product with a printed surface in accordance with the present invention; 
         FIG. 2  is a side view of the rubber product in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the rubber product in  FIG. 1 ; 
         FIG. 4  is a flow diagram showing a method for forming a printed surface on a rubber product in accordance with the present invention; 
         FIG. 5  is a 3D schematic diagram showing a plate and a printed surface layer in accordance with the present invention; 
         FIG. 6  is an exploded schematic diagram showing the plate and the printed surface layer in  FIG. 5 ; 
         FIG. 7  is a side view showing the plate and the printed surface layer in  FIG. 5 ; 
         FIG. 8  is a side view in partial section showing that a plate and a natural rubber material are placed inside a die assembly; 
         FIG. 9  is a side view in partial section showing that the plate and the printed surface layer in  FIG. 8  are separated; 
         FIG. 10  is a schematic diagram showing a bridging layer formed between a plate and a printed surface layer in accordance with the present invention; 
         FIG. 11  is a side view in partial section showing that a plate and a printed surface layer are simultaneously formed on a base in accordance with the present invention; 
         FIG. 12  is a schematic diagram showing that a plate and a natural rubber material are made in a strip from in accordance with the present invention; 
         FIG. 13  is a side view in partial section showing two printed surface layers formed on a natural rubber material in accordance with the present invention; 
         FIG. 14  is a cross-sectional view showing a plate adopting multi-colored printing in accordance with the present invention; and 
         FIG. 15  is a cross-sectional view showing a plate adopting 3D printing in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 to 3 , a rubber product with a printed surface is shown. The rubber product  10  includes a base  11  and a printed surface layer  12 . The base  11  is made of a natural rubber material that undergoes a sulfurization process. The printed surface layer  12  is printed beforehand with different colored inks made of the natural rubber material, such that the printed surface layer  12  can demonstrate variation in color and have at least one pattern or at least one label formed thereon. Surfaces of the printed surface layer  12  and the base  11  that are adjacent to each other are fused together through the sulfurization process. Upon the sulfurization process, the rubber product  10  can have portions thereon varying in height, such as a key button region  13  and a label region  14  formed on the rubber product  10 . 
     With reference to  FIGS. 4 to 9 , to form the foregoing rubber product, a method for printing the printed surface on the rubber product is provided. The method includes a pre-printing step S 1 , a pre-shrinking step S 2 , a fusing step S 3 , a separating step S 4 , and a cutting step S 5 . 
     The pre-printing step S 1  first provides a plate  20 , which is made of a material that has a melting point higher than that of the natural rubber material and may be selected from one of plastic materials, for example, PC (Polycarbonate), TPU (Thermoplastic Polyurethane), PET (Polyethylene Terephthalate), or the like, then heats the plate  20  to preshrink it, and pre-prints inks made of the natural rubber material on the plate  20  to form the printed surface layer  12  on the plate  20 . The printed surface layer  12  may have at least one pattern or at least one label each of which is printed with multiple colors. Given as one example, the at least one pattern includes the key button region  13  and the at least one label includes the label region  14  as shown in  FIG. 1 . Besides, the printed surface layer  12  may have multiple colors, at least one pattern, or at least one label printed on the plate  20  printed on the plate  20  by way of multi-layer printing or in a three-dimensional (3D) form. 
     The pre-shrinking step S 2  shrinks the plate  20  having the printed surface layer  12  by heating the plate  20  at a high temperature for the printed surface layer  12  on the plate  20  to be shrunk to a designated form. It should be pointed out that the plate  20  will not deformed during the pre-shrinking step S 2  since the plate  20  is made of the material whose melting point is higher than that of the natural rubber material. Instead, it is only the printed surface layer  12  that is shrunk by heat and gets deformed. 
     The fusing step S 3  comes after the pre-shrinking step S 2 , and after the printed surface layer  12  on the plate  20  is pre-shrunk and formed on the plate  20 , simultaneously places the plate  20  and a substrate  30  made of the natural rubber material into a die assembly  40  with the printed surface layer  12  adjacent to the substrate  30 . The die assembly  40  includes an upper die base  41  and a lower die base  42  each of which is formed with a pre-determined contour thereon. The die assembly  40  is mounted on a stamping press machine  50  through which the upper die base  41  is moved toward the lower die base  42  to perform a pressing. After the upper die base  41  falls onto the lower die base  42 , the fusing step S 3  further heats the upper die base  41  and the lower die base  42  for the substrate  30  to form the base  11  through a sulfurization process inside the die assembly  40  at a high temperature and a high pressure. A molten state occurring on surfaces of the base  11  can be resulted from the sulfurization process. As both the printed surface layer  12  and the base  11  are made of the natural rubber material, the homogeneous material property causes adjacent surfaces of the base  11  and the printed surface layer  12  to be fused together in the course of the sulfurization process, such that the printed surface layer  12  and the base  11  are formed as one piece due to fused connection. Meanwhile, the base  11  can be shaped into a predetermined form and the effect of transfer-printing the printed surface layer  12  from the plate  20  to the base  11  can be also achieved. 
     The separating step S 4  serves to separate the plate  20  from the printed surface layer  12 . Because the plate  20  and the printed surface layer  12  in the present embodiment are made of different materials and the melting point of the plate  20  is higher than that of the printed surface layer  12 , the plate  20  inside the die assembly  40  will not be fused with the printed surface layer  12  in the fusing step S 3 . After the printed surface layer  12  and the base  11  are fused as a whole to form a preliminary workpiece  60  and the die assembly  40  is chilled down, an injection mechanism  43  mounted on the lower die base  42  pushes the plate  20  upwards to separate it from the printed surface layer  12 . Additionally, in the present embodiment, an injection technique that separates the plate  20  and the printed surface layer  12  inside the die assembly  40  is adopted. Nevertheless, in practical applications, after the printed surface layer  12  and the base  11  are fused and cooled, they can be removed from the die assembly  40  and the plate  20  can then be torn off from the printed surface layer  12  to alternatively achieve the separating step S 4 . 
     The cutting step S 5  cuts the preliminary workpiece  60  into a predetermined shape of the rubber product as shown in  FIG. 1  after the base  11  and the printed surface layer  12  are fused inside the die assembly  40 , thereby allowing the printed surface layer  12  to be formed on the rubber product  10 . The cutting step S 5  here enables to cut the preliminary workpiece  50  into the rubber product  10  regardless of whether the preliminary workpiece  59  is inside the die assembly  40  or is removed from the die assembly  40 . (As being conventional techniques, either way of cutting the preliminary workpiece  50  is not elaborated here.) 
     What is worth mentioning is that owing to the sulfurization process generated through the high temperature and pressure inside the die assembly  40 , adjacent surfaces of the base  11  and the printed surface layer  12  can be fused together. Hence, the printed surface layer  12  and the base  11  have not only a better bonding strength therebetween but better resistance against abrasion and corrosion. 
     With reference to  FIGS. 10 and 11 , in the present embodiment, when a bridging layer  21  is mounted between the plate  20  and the printed surface layer  12 , the bridging layer  21  serves to bridge the printed surface layer  12  and the plate  20 , thus allowing the printed surface layer  12  and the plate  20  to be bridge-connected. After the sulfurization process at high temperature and pressure is carried out inside the die assembly  40  for the plate  20  and the base  11 , the plate  20  can be kept on the printed surface layer  12  and the plate  20  can be used as a protection layer for the printed surface layer  12 . Doing so can certainly enhance the abrasion resistance of the printed surface layer  12  and in the meanwhile make the printed surface layer  12  more vivid in color. When applied to certain special products, such as outdoor products, control panels, key boards, and the like, which need to be protected against grease, the plate  20  can prevent grease from being in direct contact with the rubber product (as shown in  FIG. 1 ), thus prolonging the life duration of the rubber product  10 . 
     With reference to  FIGS. 8 and 12 , in the present embodiment, the plate  20  and the substrate  30  can be made to take a strip form with a plenty of the printed surface layers  12  separately printed on the plate  20 . As a result, the plates  20  on the strip form and the substrate  30  can be fed into the die assembly  40  through a strip belt conveyor to attain the effect of production automation, which not only meets the demand of mass production but effectively increases production efficiency. 
     With reference to  FIG. 13 , the present embodiment is dedicated to ensure a double-sided printing effect on the substrate  30  inside the die assembly  40 . What it takes is to simultaneously mount two of the foregoing plates  20  on both top and bottom sides of the substrate  30  with two of the foregoing printed surface layers  12  on the respective plates  20  adjacent to the top and bottom sides of the substrate  30  respectively, such that the double-sided printing effect can be realized through the sulfurization process inside the die assembly  40  at the high temperature and pressure. 
     With reference to  FIG. 14 , the present embodiment serves to form the printed surface layer  12  on the heated and pre-shrunk plate  20  with various colors and height variation by way of screen-printing varying in screen mesh thickness, thereby achieving 3D transfer-printing effect or multi-colored transfer-printing effect. 
     Lastly, with reference to  FIG. 15 , the present embodiment serves to simultaneously form various indentations, such as dome-shaped indentation or rectangular indentation, patterns, or texts on the plate  20  which is malleable, by heating and pressing the plate  20  while the plate  20  is conducted with the pre-shrinking processing. Subsequently, ink containing the natural rubber material is filled in the indentations to generate the printed surface layer  12  by way of screen-printing or drop-on-demand printing, such that the plate  20  can be also utilized to fulfill the 3D transfer-printing effect. 
     In sum, the present invention pre-prints inks containing the natural rubber material on the plate  20  to form the printed surface layer  12 , places the plate  20  printed with the printed surface layer  12  and the substrate  30  made of the natural rubber material into the die assembly  40 , and performs the sulfurization process for adjacent surfaces of the printed surface layer  12  and the base  11  to be fused together and for the printed surface layer  11  to be transfer-printed on the base  12 . As such, besides the enhanced product durability, such as capability withstanding special chemical substances and enhanced abrasion-resistant capability, multiple colors, patterns or 3D forms can be transfer-printed at the same time. Therefore, the rubber product and the method for forming the printed surface can provide superior applicability and productivity and what the mechanism and the production method involved are novel and totally unconventional. 
     Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.