Method of manufacturing cushion material

Abstract: A method of manufacturing a cushion material including steps of: a mixed cotton manufacturing process in which main fibers and a plurality of types of heat-fusible fibers, which are formed of main fibers and sheath portions and whose sheath portions have different melting points, are mixed so as to make a mixed cotton; a laminating process in which the mixed cotton is spread at a substantially uniform density at an entire one forming mold of a plurality of forming molds; and a heating process in which the mixed cotton spread at the entire one forming mold is heated such that a heating temperature of portions of a cushion material which are to be formed hard differs from a heating temperature of portions of the cushion material which are to be formed soft so that a number of types of the heat-fusible fibers which melt at the portions of the cushion material which are to be formed hard is greater than a number of types of the heat-fusible fibers which melt at the portions of the cushion material which are to be formed soft.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a cushion material according to the preamble of claim 1. Description of the Related Art As illustrated as an example in Fig. 6, when a cushion material is used for a seat pad 70 of a seat cushion for a vehicle, the hardness of a central portion 70A of the seat pad 70 is low, and the hardness of both side portions 70B is high so as to improve the seating comfort for the vehicle occupant and to improve the ability of the seat pad 70 to hold the vehicle occupant. An example of a method of manufacturing such a cushion material having different hardnesses in different portions is disclosed in Japanese Patent Application Laid-Open No. 3-170112. As illustrated in Fig. 7, in this conventional method of manufacturing a cushion material, when a plurality of heat-fusible fibers, which are shaped as cotton balls, are blown into a mold 72, cotton ball shaped heat-fusible fibers 74A (the black fibers in the drawing), which are hardened to an appropriate degree by a binder in advance, are mixed and blown in together with cotton ball shaped heat-fusible fibers 74B (the white fibers in the drawing), which are not bound by a binder, at a portion 72A within the mold 72 which corresponds to a central portion of the seat pad, i.e., at a portion which is to be formed soft. The heat-fusible fibers 74A and 74B are mixed such that the density of the heat-fusible fibers 74A is higher at portions 72B corresponding to both side portions of the seat pad, i.e., at portions which are to be formed hard. Thereafter, pressure is applied as illustrated in Fig. 8. Subsequently, as illustrated in Fig. 9, the mold 72 which is filled with the heat-fusible fibers is placed within a heating portion 86 of a penetration-type heating apparatus 84 which is equipped with a hot air generating device 80 and a fan 82. The entire mold is heated at the same temperature. However, in this method of manufacturing a cushion material, the process for manufacturing the cotton ball shaped heat-fusible fibers 74A arid 74B is complicated Further, in order to form the respective hard portions and soft portions of the cushion material by manipulating the mixing ratio of the heat-fusible fibers 74A and the heat-fusible fibers 74B, it is necessary to mix the heat-fusible fibers 74A and the heat-fusible fibers 74B uniformly in accordance with the respective soft portions and hard portions. This process is extremely difficult, and irregularities in hardness due to irregularities in the densities of the fibers occur easily. From EP 0 212 082 A1 a method for manufacturing a fluid filter is known having portions of different densities. According to to the disclosed method a product comprises a randomly arranged mixture of thermoplastic fibers and fibers which are not thermoplastic or a batt made of fibers which are not thermoplastic which is impregnated with a thermoset binder. This product is wound around a heated member and is heated form the center in such a way that only the portion of the product in used heated member is melted. By doing so, the rest of said product is maintained in an unmelted state. Therefore, from this document the technical teaching can be gathered to use a material comprising thermoplastic fibers or fibers impragnated with a thermoset binder and heating only a portion of that material with the effect that within this portion the fibers will melt together, whereas within the rest of the material the fibers are not melted together. The object underlying the invention is to provide a method of manufacturing a cushion material having harder and softer portions which is simple and which can be carried out easily. This object is achieved by a method according to new claim 1. According to this method main fibers are used and a plurality of different heat-fusible fibers wherein the main fibers are unsheathed and further sheated fibers having different melting points are used. This material is spread into a mold as a substantially uniform density. Actually, it is the greatest advantage of the new method that the material, the mixed cotton can be spread at the uniform density at the entire forming mold whereby the manufacturing process can be considerably simplified. To achieve harder portions and softer portions, the portions which have a greater hardness or heated by temperature higher than the heating temperature of portions which should be softer. Such a different heating can be easily achieved, for example by a device as shown in fig. 1 of the application documents. The number of fusion points of the heat-fusible fibers of the hard portions of the cushion material is greater than the number of fusion points of the heat-fusible fibers of the soft portions so that a cushion material having hard portions and soft portions is manufactured. Accordingly, in the present invention, there is no manufacturing process for manufacturing heat-fusible fibers which are shaped as cotton balls, as there is in the conventional art. The manufacturing process of the present invention is simple, and there is no need to vary the densities of the heat-fusible fibers. Therefore, it is difficult for irregularities in hardness to be generated in the portions which are to be formed soft and in the portions which are to be formed hard. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view illustrating a penetration-type heating apparatus used in a heating process of a method of manufacturing a cushion material relating to an embodiment of the present invention. Fig. 2A is a schematic view illustrating a mixed cotton of the method of manufacturing a cushion material relating to the embodiment of the present invention. Fig. 2B is a schematic view illustrating a state of heat-fusible fibers of a hard portion of a seat pad manufactured by the method of manufacturing a cushion material relating to tile embodiment of the present invention. Fig. 2C is a schematic view of a state of heat-fusible fibers of a soft portion of the seat pad manufactured by the method of manufacturing a cushion material relating to the embodiment of the present invention. Fig. 3 is a schematic view illustrating a mold clamping process of the method of manufacturing a cushion material relating to the embodiment of the present invention. Fig. 4 is a perspective view illustrating the seat pad of a seat cushion for a vehicle manufactured by the method of manufacturing a cushion material relating to the embodiment of the present invention. Fig. 5 is a sectional view taken alon line 5-5 of Fig. 4. Fig. 6 is a sectional view illustrating a seat pad of a seat cushion for a vehicle manufactured by a method of manufacturing a cushion material relating to a conventional example. Fig. 7 is a schematic view illustrating a laminating process of the method of manufacturing a cushion material relating to the conventional example. Fig. 8 is a schematic view illustrating a mold clamping process of the method of manufacturing a cushion material relating to the conventional example. Fig. 9 is a schematic view illustrating a penetration-type heating apparatus used in a heating process of the method of manufacturing a cushion material relating to the conventional example. DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a method of manufacturing a cushion material relating to the present invention will be described in accordance with Figs. 1 through 5. As illustrated in Fig. 4, a seat pad 10 of a seat cushion for a vehicle manufactured by the method of manufacturing a cushion material of the present embodiment is formed such that side portions 10B, 10C protrude upwardly with respect to a seat surface central portion 10A. As shown in Fig. 5, the hardness of the seat surface central portion 10A of the seat pad 10 is low, and the hardness of the side portions 10B, 10C is high so that the seat is comfortable for a vehicle occupant. Further, because the side portions 10B, 10C reliably restrain the hips of the vehicle occupant, it is difficult for the occupant to slide towards the sides of the seat. Next, the method of manufacturing the seat pad 10 will be described in detail. As an example, the following three types of fibers illustrated in Table 1 are used: main fibers (melting point: 250°C ) and two types of heat-fusible fibers A, B, which respectively have the same core portion but have a sheath portion of a different melting point at the outer periphery of the core portion. The melting point of the sheath portion of the heat-fusible fibers A is 150°C and that of the heat-fusible fibers B is 180°C. The fibers are mixed uniformly so that the mixing ratio of the main fibers, the heat-fusible fibers A and the heat-fusible fibers B is 65%, 20%, 15%. As illustrated in Fig. 2A, a mixed cotton 18 formed of main fibers 12, heat-fusible fibers A 14, and heat-fusible fibers B 16 is thereby manufactured. (Hereinafter, this process will be referred to as the "mixed cotton manufacturing process"). Next, as illustrated in Fig. 3, the mixed cotton 18 manufactured in the mixed cotton manufacturing process is spread evenly on a lower mold 20 which forms the upper surface of the seat pad 10. (Hereirlafter, this process will be referred to as the "laminating process"). The lower mold 20 is formed of punching metal having a predetermined rate of hole area (i.e., the area of the holes per unit area). An upper mold 24, which is similarly formed of punching metal and which is used to form the bottom surface of the seat pad 10, is clamped with the lower mold 20 (hereinafter, the "mold clamping process"). The mixed cotton 18 is to be measured and spread by taking the volume of the interior of the molds into consideration so that the overall density of the entire seat pad 10 is a predetermined value when the molds are clamped. Therefore, as can be seen in Figs. 1 through 3, the mixed cotton 18 is compressed by the clamping of the molds such that a predetermined internal compressive force is generated. Next, as illustrated in Fig. 1, the clamped mixed cotton 18 is set within a heating portion 26 of a penetration-type heating apparatus 25. The interior of the heating portion 26 of the penetration-type heating apparatus 25 is divided into a low temperature heating portion 26A and high temperature heating portions 26B, 26C. The low temperature heating portion 26A heats a seat surface central portion corresponding portion 18A of the clamped mixed cotton 18 which corresponds to the seat surface central portion 10A of the seat pad 10. The high temperature heating portions 26B, 26C heat side portion corresponding portions 18B, 18C of the clamped mixed cotton 18 which correspond to the side portions 10B, 10C of the seat pad 10. The low temperature heating portion 26A is connected, via a duct 30, to a hot air generating device 32 and to a fan 34 which blows heat generated by the hot air generating device 32. The seat surface central portion corresponding portion 18A of the clamped mixed cotton 18 is thereby heated to, for example, 170°C. Further, the high temperature heating portions 26B, 26C of the penetration-type heating apparatus 25 are connected, via respective ducts 36, to a hot air generating device 38 and to a fan 40 which blows heat generated by the hot air generating device 38. The side portion corresponding portions 18B, 18C of the clamped mixed cotton 18 are thereby heated to, for example, 200°C. By heating the clamped mixed cotton 18 in this way, both the sheath portions of the heat-fusible fibers A 14 and the sheath portions of the heat-fusible fibers B 16 are melted by heat as illustrated in Fig. 2B at the side portion corresponding portions 18B, 18C of the clamped mixed cotton 18. Therefore, the main fibers 12, the heat-fusible fibers A 14 and the heat-fusible fibers B 16 are fused together at fusion points P. On the other hand, as illustrated in Fig. 2C, at the seat surface central portion corresponding portion 18A of the clamped mixed cotton 18, only the sheath portions of the heat-fusible fibers A 14 are melted by heat. Therefore, the heat-fusible fibers A 14 fuse with the main fibers 12 and the heat-fusible fibers B 16 at the fusion points P. Compared to the number of fusion points P at the seat surface central portion corresponding portion 18A of the mixed cotton 18, there are a large number of fusion points P at the side portion corresponding portions 18B, 18C of the mixed cotton 18. The hardness of the side portion corresponding portions 18B, 18C of the mixed cotton 18 which correspond to the side portions 10B, 10C of the seat pad 10 is high as compared with the hardness of the seat surface central portion corresponding portion 18A of the mixed cotton 18 which corresponds to the seat surface central portion 10A of the seat pad 10. In other words, heating (i.e., heating processing) is carried out at different temperatures for the side portion corresponding portions 18B, 18C of the clamped mixed cotton 18 which are to be formed hard and for the seat surface central portion corresponding portion 18A which is to be formed soft. In this way, at the side portion corresponding portions 18B, 18C of the clamped mixed cotton 18 which are to be formed hard, the number of types of heat-fusible fibers whose sheath portions melt (i.e., two types: the heat-fusible fibers A 14 and the heat-fusible fibers B 16) is greater than the number of types of heat-fusible fibers (i.e., one type: the heat-fusible fibers A 14) which melt at the seat surface central portion corresponding portion 18A which is to be formed soft. Thereafter, a cooling process and a process for removing the seat, pad 10 from the molds, which are both commonly-known processes, are carried out so that the seat bad 10 is completed. As described above, in the present invention, there is no manufacturing process for manufacturing the cotton ball shaped heat-fusible fibers as there is in the conventional art. Further, the manufacturing process of the present invention for manufacturing the mixed cotton is simple, and there is no need to vary the densities of the heat-fusible fibers. Therefore, it is difficult for irregularities in hardness to be generated in the portions which are to be formed soft and in the portions which are to be formed hard. In the present embodiment, the seat surface central portion corresponding portion 18A of the clamped mixed cotton 18 which is to be formed soft is heated to 170°C , and simultaneously, the side portion corresponding portions 18B, 18C which are to be formed hard are heated to 200°C. However, an alternative method may be used in which the entire mixed cotton 18 clamped in the molds is heated to 170°C, and thereafter, only the side portion corresponding portions 18B, 18C of the clamped mixed cotton 18 which are to be formed hard are heated to 200°C. Further, in order to vary the hardness of the seat pad 10, the mixing ratio of the heat-fusible fibers A 14 and the heat-fusible fibers B 16 may be varied. For example, if the main fibers 12 are decreased and the heat-fusible fibers A 14 are increased, the entire seat pad 10 becomes more hard. On the other hand, if the main fibers 12 are decreased and the heat-fusible fibers B 16 are increased, only the side portions 10B, 10C of the seat pad 10 become harder. Further, if the heat-fusible fibers A 14 are decreased and the heat-fusible fibers B 16 are increased, the seat surface central portion 10A of the seat pad becomes more soft and the side portions 10B, 10C of th seat pad 10 become more hard. Moreover, in the present embodiment, the mixed cotton 18 is formed of the main fibers 12 and two types of heat-fusible fibers having different sheath portion melting points. However, the mixed cotton 18 may be formed of a main fiber and three or more types of heat-fusible fibers having different melting points of the sheath portions. In the present embodiment, a method of manufacturing a seat pad of a seat cushion for a vehicle is described. However, the method of manufacturing a cushion material of the present invention is not limited to the manufacturing of seat pads of seat cushions for vehicles. The method of the present invention is directed toward the manufacturing of cushion materials in general, and may also be applied to chairs, beds and the like.

Claims: A method for manufacturing a cushion material comprising the steps of: a mixed cotton manufacturing process in which fibers are mixed so as to make a mixed cotton; a laminating process in which said mixed cotton is spread at an entire one forming mold (20) of a plurality of forming molds (20, 24); and a heating process in which said mixed cotton spread at said entire one forming hold (20) is heated; characterized in that said mixed cotton comprises main fibers (12) and a plurality of types of heat-fusible fibers (14, 16) which are formed of main fibers as core portions and sheath portions and whose sheath portions have different melting points, and that said mixed cotton is spread at a substantially uniform density at said forming mold (20) and is heated such that a heating temperature of portions (18B, 18C) of a cushion material which are to be formed hard is higher than a heating temperature of portions (18A) of said cushion material which are to be formed soft so that a number of types of said heat-fusible fibers (14, 16) which melt at the portions (18B, 18C) of said cushion material which are to be formed hard is greater than a number of types of said-heat-fusible fibers (14, 16) which melt at the portions of said cushion material which are to be formed soft. A method of manufacturing a cushion material according to claim 1, wherein said heating process includes a first mixed cotton heating process in which said mixed cotton is heated at a first temperature which is lower than a melting point of said main fibers and which is higher than a melting point of said sheath portions of at least one type of said heat-fusible fibers (14, 16) of said plurality of types of said heat-fusible fibers (14, 16), and a second mixed cotton heating process in which said mixed cotton is heated at a second temperature which is lower than the melting point of said main fibers (12) and which is higher than said first temperature. A method of manufacturing a cushion material according to claim 2, wherein in said heating process, said first mixed cotton heating process and said second mixed cotton heating process are effected simultaneously. A method of manufacturing a cushion material according to claim 2, wherein in said heating process, said second mixed cotton heating process is effected after said first mixed cotton heating process. A method of manufacturing a cushion material according to claim 4, wherein in said first mixed cotton heating process, said mixed cotton at the portions (18B, 18C) of said cushion material which are to be formed hard and said mixed cotton at the portions (18A) of said cushion material which are to be formed soft are heated simultaneously. A method of manufacturing a cushion material according to claim 1, wherein in said mixed cotton manufacturing process, mixing is effected such that respective proportions of said main fibers (12) included in said mixed cotton and of said plurality of types of said heat-fusible fibers (14, 16) included in said mixed cotton are constant throughout said entire mixed cotton. A method of manufacturing a cushion material according to claim 1, wherein in said laminating process, said mixed cotton is laminated so that a density of said mixed cotton is substantially uniform when said mixed cotton is compressed by said plurality of forming molds (20, 24). A method of manufacturing a cushion material according to claim 1, further comprising the step of: a mold clamping process in which said mixed cotton which was spread in said laminating process is compressed and formed by said plurality of forming molds (20, 24). A method of manufacturing a cushion material according to claim 8, wherein in said heating process, said mixed cotton and said plurality of forming molds (20, 24) are heated in a state in which said mixed cotton is compressed in said mold clamping process. A method of manufacturing a cushion material according to claim 1, wherein said sheath portions of said plurality of types of said heat-fusible fibers are provided at respective outer peripheries of said main fibers (12) which correspond to said heat-fusible fibers (14, 16). A method of manufacturing a cushion material according to claim 1, wherein during said laminating process said mixed cotton is spread at a substantially uniform density at an entire one forming mold (20) of a plurality of forming molds (20, 24) and afterwards during a mold clamping process said mixed cotton which was spread in said laminating process is compressed and formed by said plurality of forming molds (20, 24). A method of manufacturing a cushion material according to claim 1, wherein said heating process is effected by blowing hot air.

Inventors: NOMIZO FUMIO, NOMIZO, FUMIO
Applicants: TOYOTA MOTOR CO LTD, TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1993
Main classification: D04H1
IPC codes: D04H1, B68G5, A47C27