Method for manufacturing the rim of a steering wheel for vehicles

Abstract: A rim of a steering wheel for vehicles is manufactured by (A) forming a molding member of a urethane material which constitutes a part of the rim of a steering wheel; (B) forming a masking portion by attaching a first mask member to a part of a surface of the molding member; (C) forming a first transfer surface by performing a hydraulic transfer on a surface where the first mask member does not adhere; (D) forming a coating film on the first transfer surface; (E) removing the first mask member to reveal a surface where transfer is not performed; (F) performing a second hydraulic transfer on the surface where transfer is not performed; and (G) cleaning the coating film. Thus, a clear pattern can be formed without overlapping or unsmooth matching of a pattern of a transfer film.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rim of a steering wheel for vehicles, and more particularly, to a method for manufacturing a rim of a steering wheel of high quality using a hydraulic transfer method. 2. Description of the Related Art FIG. 1 shows an example of a method for manufacturing a rim of a steering wheel for vehicles. As shown in FIG. 1, a first molding portion 2 formed of soft PVC or urethane is formed on and around a hub core 1. Referring to FIG. 2, the first molding portion 2 is wrapped by leather 3, and a wood portion 4 is formed around the remaining hub core 1 by processing wood suitable for the shape of the hub core 1 and attaching the processed wood thereto. Alternatively, the wood portion 4 can be formed by layering wood laminae, cut in the form of a sheet, or mixing sawdust with resin and molding the mixture and attaching a thin wood sheet thereon. However, the above manufacturing methods are complicated and not suitable for mass production. Also, the manufacturing cost is high. Japanese Patent Publication No. 61005981 discloses a method for manufacturing a rim of a steering wheel for vehicles performing only once a hydraulic transfer onto a surface of the rim by using one transfer sheet. As a consequence, as the transfer sheet is extended when a hydraulic transfer is performed only once by using one transfer sheet, the wood pattern is significantly deformed. SUMMARY OF THE INVENTION To solve the above problems, it is an objective of the present invention to provide a method for manufacturing a rim of a steering wheel for vehicles using a hydraulic transfer method so that a portion of the rim can be manufactured in a large quantity at a relatively low cost while achieving a high quality appearance thereof. It is another objective of the present invention to provide a method for manufacturing a rim of a steering wheel for vehicles in which a transferring process is performed using a mask tape or a rubber jig (hereinafter, referred to as a mask member) so that various wood patterns and other patterns can be available. Also, it is yet another objective of the present invention to provide a method for manufacturing a rim of a steering wheel for vehicles by which accurate and clear match of pattern is possible on a steering wheel whose shape is not suitable for such an hydraulic transfer in one single step. Accordingly, to achieve the above objective, there is provided a method for manufacturing a rim of a steering wheel for vehicles, which comprises the steps of: (A) forming a molding member of a urethane material which constitutes a part of the rim of a steering wheel; (B) forming a masking portion by attaching a first mask member to a part of a surface of the molding member; (C) forming a first transfer surface by performing a hydraulic transfer on a surface where the first mask member does not adhere; (D) forming a coating film on the first transfer surface; (E) removing the first mask member to reveal a surface where transfer is not performed; (F) performing a second hydraulic transfer on the surface where transfer is not performed; and (G) cleaning the coating film. To achieve the second objective, there is provided a method for manufacturing a rim of a steering wheel for vehicles, which comprises the steps of: (A) forming a molding member of a urethane material which constitutes a part of the rim of a steering wheel; (B) forming a masking portion by attaching a first mask member to a part of a surface of the molding member; (C) forming a first transfer surface by performing a hydraulic transfer on a surface where the first mask member does not adhere; (D) attaching a second mask member to the first transfer surface and removing the first mask member; and (E) performing a second hydraulic transfer on the surface where the second mask member does not adhere. To achieve the third objective, there is provided a method for manufacturing a rim of a steering wheel for vehicles, which comprises the steps of: (A) forming a molding member of a urethane material which constitutes a part of the rim of a steering wheel; (B) forming a masking portion by attaching a first mask member to a part of a surface of the molding member; (C) marking a junction line by marking a blade scar approximately at a middle portion of the mask member of the rim of a steering wheel which is placed on a horizontal rotatable table and removing a part of the mask member disposed under the junction line; (D) covering an upper portion of the mask member which is not removed; (E) performing a transfer on a lower surface under the junction line and cleaning and drying the transferred surface and coating a PVA solution on the transferred surface and drying the coated surface; (F) marking a separation line by placing the rim of a steering wheel on the horizontal rotatable table and adjusting and fixing the height of a blade to be disposed about 0.05-0.2 mm lower than that in the step (C); and (G) removing the remaining mask member and a part of a PVA film and performing a second transfer and cleaning and drying a second transfer surface. BRIEF DESCRIPTION OF THE DRAWINGS The above objectives and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: FIGS. 1 and 2 are views showing a portion of a rim of a steering wheel according to a conventional manufacturing method; FIG. 3 is a view showing a rim of a steering wheel manufactured according to a preferred embodiment of the present invention; FIG. 4 is a view showing a portion of steps for manufacturing a portion of a rim of a steering wheel in a hydraulic transfer method using a mask according to the present invention; FIGS. 5a and 5b are views for explaining the subsequent manufacturing steps after the step shown in FIG. 4; FIG. 6 is a view showing a state in which the transfer film 6 and the first mask member 8 are formed correctly; FIG. 7 is a view showing a state in which the transfer film 6 and the first mask member 8 are formed incorrectly; FIGS. 8a through 8d are views for explaining a manufacturing method according to another preferred embodiment of the present invention; FIG. 9 is a view showing a state in which the first transfer surface 11 and the second mask member 12 are formed according to another preferred embodiment of present invention; FIG. 10 is a view showing a state in which the transfer film 6 and the second mask member 12 are formed according to another preferred embodiment of present invention; FIG. 11 is a view showing a state in which patterns are not matched correctly; FIG. 12 is a view showing an example of a pattern of the transfer film; FIG. 13 is a view showing a steering wheel to which the transfer film of FIG. 12 is applied; FIGS. 14 and 15 are views showing another preferred example of a pattern and a steering wheel adopting the pattern; FIGS. 16 and 17 are views showing yet another preferred example of a pattern and a steering wheel adopting the pattern; FIG. 18 is a view showing yet another preferred embodiment of the present invention; FIG. 19 is a view showing an apparatus for forming a coupling line on the mask member of FIG. 18; FIGS. 20 and 21 are views for explaining the subsequent steps after the step shown in FIG. 19; FIG. 22 is a view showing the position of the blade 25 of the blade holder 24 of the apparatus shown in FIG. 19; and FIG. 23 is a partial sectional view for explaining the forming and incision of the PVA protective film described in FIG. 21. DETAILED DESCRIPTION OF THE INVENTION In the following description the embodiments not felling within the scope of the claims, particularly those including a coating film as masking portion, are not part of the invention. Referring to FIG. 3, according to the present invention, a second molding portion 5 is formed on and around the hub core 1 of FIG. 1 and then a pattern 15 applied on it in a hydraulic transfer method. The second molding portion 5 is formed of soft or hard urethane by molding urethane, preferably hard urethane, and performing the hydraulic transfer method according to the present invention which will be described later. The second molding portion 5 can be formed of a material made by adding sawdust into resin, In addition to the above materials. Any material such as ABS (acrylonitrile butadiene styrene), PP (polypropylene) or PVC (polyvinyl chloride) can be used therefor. However, the material of the molding portion of a steering wheel must meet various test requirements, particularly, the material should not generate sharp fragments to harm humans in a crash test. In consideration of the above and as a result of the crash test, urethane which is used for the present invention meets all requirements and is considered to be preferable. FIG. 4 shows a method of transferring a predetermined pattern on a portion of the second molding portion 5 according to the present invention. For example, the second molding portion 5 only is separated from the steering wheel. A bent circular bar, which is the result of the above separation, is masked with a first mask member 8 lengthwise and half the circumference of the section of the bar. A tape or rubber is used for the first masking member 8. A transfer film 6 is placed to float on water 7 and a portion that is not masked is located to the bottom and pushed downward above the transfer film 6. Then, a first transfer is performed due to hydraulic pressure. Consequently, the surface where the transfer is performed has a pattern, e.g., a wood pattern. After cleaning and drying the transferred portion of the bent bar, the surface where the first transfer is performed is coated with PVA (polyvinyl alcohol) solution and dried. When the first mask member 8 that is a tape is removed, a PVA coating film 9 is formed on the patterned area and the masked area is revealed clearly, as shown in FIG. 5a. The PVA solution above is water-soluble. When the PVA solution is coated and dried, a film is formed to protect a printed pattern layer formed thereunder and prevent overlapping of pattens. Since the coating film in the present invention is not limited to PVA, other materials which are water-soluble and can form a film when dried to protect a printed pattern layer already formed thereunder without discoloration or damage can be used therefor. For example, starch (farina) can be used as the PVA solution. The second transfer is performed on the remaining surface in the same manner as the first transfer. Here, the transfer may be made on a part of the area where a pattern is already formed and the coating film 9 is formed thereon. However, after the second transfer, when the area where a pattern is already formed and the coating film 9 is formed thereon is cleaned with hot water, preferably, over about 30°C, the area is melted and washed out so that the pattern formed on the coating film 9 through the second transfer is removed and the pattern formed through the first transfer is clearly revealed. When the resultant from the above cleaning step is dried, as shown in FIG. 5b, a clearly printed pattern can be formed without damage to the shape of the pattern such as overlapping, extending, or distorting of patterns. Also, even though the edge of the first mask member 8 is not accurately attached in a form of covering about half the surface to be subject to the transfer, patterns can be accurately matched when the second transfer is performed. Preferably, the edge of an end portion of the first mask member 8 closely contacting an object subject to the transfer is formed to be slanted at an angle of 60° or less with respect to the horizontal surface as shown in FIG. 6. Then, the patterns separately transferred through the first and second transfers are smoothly connected at the boundary area between the patterns. If the edge of the first mask member 8 is formed over 60°, for example, nearly 90° as shown in FIG. 7, bubbles 10 are trapped between the transfer film 6 and the first mask member 8 and cannot escape therefrom, thus, when a transfer is performed, a print is not made on the connection area between the first and second transfers. As a result, the portion where no transfer is made becomes a form of a strip. In the above preferred embodiment, a pattern is accurately and separately transferred on the hard urethane molding portion of a steering wheel that is an object to be subject to the transfer using the first mask member 8 and the coating film 9 through the first and second transfer steps. However, since the present invention is not limited to the above embodiment, two or more patterns can be separately transferred on the same surface through first, second and third transfer steps so that various patterns can be obtained. FIGS. 8a through 8d show another preferred embodiment of the present invention. As in the above embodiment, a first transfer surface 1 is first formed on the bottom surface. After the first transfer surface 1 is cleaned and dried, the first mask member 8 is removed, as shown in FIG. 4, and the first transfer surface 11 is revealed as shown in FIG. 8a. A second mask member 12 where the transfer is performed is wrapped on the first transfer surface 11 as shown in FIG. 8b. Next, when the other half surface where the transfer is not performed is turned 180° and a transfer is performed thereon, a second transfer surface 13 is formed as shown in FIG. 8c. Finally, the second transfer surface 13 is cleaned and dried, or dried without cleaning, and the second mask member 12 shown in FIG. 8c is removed. Then, a clear printed pattern can be formed as shown in FIG. 8d. It is preferable that, in the step of FIG 8b, the edge of the second mask member 12 adheres closely to the first transfer surface 11 short of its edge, leaving the first transfer surface with a predetermined gap (c) as shown in FIG 9. Then, a smooth connection of the patterns is achieved in the area where the first and second transfers are made. That is, as shown in FIG. 10, when the transfer film 6 is used for transfer after the second mask member 12 is attached, since no transfer is made as far as the distance (c), the second mask member 12 is coupled with the distance (c) such that the surface where the pattern is already formed can be revealed as long as a predetermined length. The distance is preferably 0.1-0.4 mm. Although the distance can be slightly different according to the members, in a particular case of manufacturing a steering wheel for vehicles, a set of 0.2 mm results in an accurate match of patterns according to actual experiences. When the distance (c) is too narrow, a non-transfer strip 14 is generated as shown in FIG. 11. If the distance (c) is too wide, patterns are overlapped on the transfer surface. Although a separate masking method using a mask member through first and second transfer steps is described in the above preferred embodiment, the present invention is not limited thereto. A more accurate and complicated pattern can be transferred by a method of masking through three or more transfer steps. Also, although the pattern of the transfer film used in the hydraulic transfer method according to the present invention is described to be a typical wood pattern for showing the texture of wood, the present invention is not limited thereto. Any form of pattern, for example, a stone pattern, a latticed carbon fiber pattern or a metal surface pattern can be used therefor. For example, when a steering wheel is hydraulic-transferred to have the texture of a wood pattern, a transfer film having a linear wood pattern as shown in FIG. 12 results in an unnatural shape as shown in FIG. 13, not giving a texture of wood and being inferior in view of aesthetics. It is preferable to use the transfer film 6 having a pattern as shown in FIG. 14. As shown in FIG. 15, a pattern is formed along a rim of a steering wheel. The pattern as shown in FIG. 14 can be prepared and designed using computer graphics to be suitable for the shape of the rim. Another preferred embodiment of the pattern of the transfer film 6 is shown in FIG. 16. The entire circular pattern above designed using computer graphics can be transferred on a rim of a steering wheel with one transfer. FIG. 17 shows the steering wheel where the wood pattern is smoothly connected in a circular form. FIGS. 18 through 23 show yet another preferred embodiment of the present invention in which a mask member is used. As shown in FIG. 18, a mask member 18 of a strip shape having a width of about 4-5 mm is attached to the inner and outer circumferential parts of a rim of a steering wheel 22. The rim of the steering wheel 22 is placed on an upper plate 21 of a horizontally rotatable table 20 and fixed by a clamp 23, as shown in FIG. 19. A blade holder 24 capable of adjusting the height of a blade 25 is installed on the upper plate 21. The blade 25 is fixedly held by the blade holder 24 such that the height of the blade 25 can be flushed with a junction line 8a which is a dotted line marked approximately in the middle of the mask member 18. In a state in which the rim of the steering wheel 22 is fixed and the blade holder 24 slightly presses the outer circumferential surface of the rim of the steering wheel 22, as the table 20 rotates, a blade scar is made along the junction line 8a. Then, the mask member 18 of the lower portion of the junction line 8a is removed as shown in FIG. 20. The above step of incising the mask member 18 adhering to the rim of the steering wheel 22 is performed from the inner and outer circumferential side of the rim of the steering wheel 22 using the blade holder 24. Also, the mask member 18 can be incised by rotating the upper plate 21 where the steering wheel 22 is fixed and fixedly holding the blade holder 24 with a hand. On the contrary, the mask member 18 can be incised by rotating the blade holder 24 from the inner and outer circumferential side of the rim of the steering wheel 22 while keeping the upper plate 21 where the rim of the steering wheel 22 is fixed not to rotate. As shown in FIG. 21, a PVA solution is coated on a surface b and dried and transfer is performed on a surface a . Here, the PVA solution is made by mixing PVA and water in a weight ratio of 1(PVA):12-16(water) and completely solving the mixture at the temperature of 60-70°C and adding alcohol to be at 15-20wt%. The above PVA solution dries fast and forms the thinnest film so that the working speed is faster and spraying the PVA solution is possible and a cleaning step is made easy. After the surface a where the transfer is made is cleaned and dried, the PVA solution is coated thereon and dried and the steering wheel 22 is installed on the table 20. As shown in FIG. 22, the height of the blade 25 disposed at the right side in the drawing is adjusted to be about 0.05-0.2 mm lower than the height of the left blade 25 used previously to draw a (dotted) separation line 8b as shown in FIG. 21. The remaining mask member 18 and a part of the PVA film shown in FIG. 21 are removed and a second transfer is performed on the surface b . After cleaning and drying the surface b , a clear transfer is completed so that no non-transferred surface is generated and there is no overlapping of the transferred patterns. FIG. 23 shows a magnified section of a major portion around the mask member 18 shown in FIG. 21 before the transfer on the surface b is performed. As shown in the drawing, a PVA coating film 19 is formed overlapping the mask member 18. Thus, when the mask member 18 is removed by forming a separation line 8b which is a second blade scar about 0.05-0.2 mm under the blade scar of the middle junction line 8a, the PVA protective film 19 and the mask member 19 formed from and above the separation line 8b are removed. In an another preferred embodiment of FIG. 21, the same result can be obtained by attaching a mask member, instead of coating a PVA solution on the surface b . In the former method, when a PVA solution is coated on the surface a, the surface b should not be stained with the PVA solution. Also, since an additional mask member is not needed in the above method, the mask member can be saved and a step relating to attachment of the mask member can be omitted. Meanwhile, in the latter method, when the PVA solution is coated on the surface a , since the surface b is covered with the mask member, the PVA solution can be coated by a spraying or dipping method so that the working time can be reduced. The preferred embodiments described with reference to FIGS. 18 through 23 enable a considerably fast working speed so that mass production is possible and uniformity of products is improved, lowering the defective rate. As described above, according to the present invention, since a wood texture as a natural wood can be represented at a cost relatively lower by 2-3 times or more, a rim of a steering wheel of high quality can be manufactured in mass. Also, the present invention for forming a wood pattern, for example, on a hard urethane gives not only the same touch and feel as that of natural wood, but also superior texture. Furthermore, a transfer of a pattern or picture on a product having a complicated bent portion which is difficult to transfer a pattern, for example, a rim of a steering wheel for vehicles as well as cases for various musical instruments or a fishing rod, can be clearly performed without an unsmooth connection portion or a step line between patterns or pictures. Although the above description of the present invention covers a method for manufacturing a rim of a steering wheel for vehicles, the present invention is not limited thereto. It is obvious that a transfer can be performed on surfaces of any kind of product such as plastics, aluminum, steel, or wood, having a complicated bent or curved portion.

Claims: A method for manufacturing a rim of a steering wheel for vehicles, said method comprising the steps of: (A) forming a molding member of a urethane material which constitutes a part of said rim of a steering wheel; (B) forming a masking portion by attaching a first mask member (8) to a part of a surface of said molding member; (C) forming a first transfer surface (11) by performing a hydraulic transfer on a surface where said first mask member (8) does not adhere; (D) attaching a second mask member (12) to said first transfer surface (11) and removing said first mask member; (E) performing a second hydraulic transfer on the surface where the second mask member (12) does not adhere; wherein in said step of attaching said second mask member (12), said second mask member (12) has its edge attached leaving a predeterminated gap (c) uncovered from the edge of said first transfer surface (11). The method as claimed in claim 1, wherein said distance (c) is 0.1-0.4 mm. The method as claimed in claim 2, wherein said distance (c) is 0.2 mm. The method as claimed in claim 1, wherein an edge of an end portion of said first mask member which adheres to a surface of said molding member of said rim of a steering wheel is formed to be slanted at an angle of 60°C or less with respect to the surface of said molding member, viewed from the side thereof.

Inventors: CHO YOUN-SOO, CHO, YOUN-SOO
Applicants: CHO YOUN-SOO, CHO, YOUN-SOO
Application year: 1999
Main classification: B62D1
IPC codes: B44C1, B62D1