1. Field of the Invention
The present invention relates to an apparatus for manufacturing a seat including an automotive seat, and is particularly concerned with an apparatus for forming a seat, of such integral foaming type wherein a trim cover assembly and a foam base material are foamed together in a die into an integral unit of seat having an outer cover member and a foam cushion member covered integrally therewith.
2. Description of Prior Art
An integral foaming with a trim cover assembly into a certain seat, such as for example, an automotive seat, has been effected in view of easy operation requiring no adhesive, and various kinds of apparatuses therefor have been provided and known. Particularly, let us focus an apparatus having three die members for such integral foaming: As known from the Japanese Patent Laid-Open Publication No. 49-76653, basically the apparatus of this kind includes a lower die member upon which a trim cover assembly is placed, an intermediate die member having a contour similar to the body of seat, which is to be mounted upon the lower die member, wherein the trim cover assembly is retained between the lower and intermediate die members, and an upper die member which is to be mounted upon the opened side of the intermediate die member. Accordingly, a hollow is defined within those three die members, in which a foaming base material is injected and then a foaming is effected therein in order for the trim cover assembly to be integrally foamed with a foamed resultant cushion member.
A typical explanation on this sort of apparatus will be given now by referring to FIGS. 1 through 3.
As shown in FIG. 1, the apparatus comprises an upper die member (3) whose shape conforms to that of the bottom surface of a resulting seat, which is formed at its center area with an injection port (31), through which a foaming base material is to be injected, an intermediate die member (1') which in composed of three separate die pieces (1a') (1b') (1c') although not clearly shown and reference may be made to FIG. 4 from which the designation (1c') being not shown should be assumed as generally corresponding to (1c) for understanding, the die pieces (1a')(1b')(1c') being to be put togther and intended for forming a body of resulting cushion member (5'), and a lower die member (2) upon which is placed a trim cover assembly (4). The trim cover assembly (4) consists essentially of a seating surface portion (4a) and a side wall portion (4b), the seat surface portion (4a) including an outer cover member (41) made of a woven fabric or the like, a foam wadding (42) formed of a slab-type urethane foam material, and a wadding cover (43) of non-woven fabric or the like, and the side wall portion (4b) being a single cover element which covers a corresponding side wall part of a cushion member. The illustrated trim cover assembly (4) has a pair of decorative constricted parts (4c)(4c) formed in the seating surface portion (4a). The side wall portion (4b) is at its one end parts sewn with the peripheral parts of the seating surface portion (4a) at a sewn jointed point (4f), with the terminal end (4g) of the seating surface portion (4a) protruding outwardly from the sewn jointed point (4f). The lower die member (2) is, therefore, provided at its molding surface with a pair of support projections (21) (21) each being disposed in correspondence with the respective two constricted parts (4c) (4c) associated with the trim cover assembly (4), and the entire diameter or surface area of the lower die member (2) is designed relatively smaller than the outer diameter of the intermediate die member (1') as shown.
The molding surface of the lower die member (2) is formed such that its surface area is generally similar to that of the seating surface portion (4a), in order that the trim cover assembly (4), which is initially turned inside out, is placed on the lower die member (2), with the side wall portion (4b) depending around the peripheral edges of the lower die member (2), and the constricted parts (4c) (4c) being supported upon the projections (21) (21) respectively as shown.
In operation, the first step is to place the turned-over trim cover assembly (4) upon the lower die member (2) as shown in FIG. 1. The intermediate die member (1'), after having its three die pieces (1a') (1b') (1c') put together, is then pressedly placed on that lower die member (2) so that the lower contact edges (13A) (13B) of the intermediate die member (1') are pressed in place upon the peripheral edges of the lower die member (2), thereby collapsing and retaining therebetween the peripheral end areas of the seating surface portion (4a) of the trim cover assembly (4), whereupon a retained areas (4d) (4d') are defined in such peripheral end areas of the trim cover assembly (4), and therefore, as can be seen from FIGS. 1 and 2, the seating surface portion (4b) is pressingly retained at those retained areas (4d) (4d') between the contact ends (13A) (13B) of the intermediate die member (1') and the peripheral end parts of the lower die member (2). At the same time, the upper die member (3) is fitted on the upper opened side of the intermediate die member (2). Consequently, those three die members (3) (1') (2) are fitted securely together to form a unit of seat forming die having a hollow therein. Then, a base foaming material is injected through the port (31) into the hollow of thus-assembled die unit. A foaming is effected in the die unit so as to produce a foam cushion member (5') which is integral with the seating surface portion (4a) of the trim cover assembly (4), as in FIG. 2.
The above-described foaming process has been a common way, but the drawback has been with a resulting seat produced therefrom, in that an undesired projected area (P) is created at the corner of the seat as shown in FIG. 3. The reason is that, as best shown in FIG. 2, at the time when the lower contact end (13A) is pressed against the peripheral end area of the lower die member (2), the corresponding peripheral end part (at 4e) of the seating surface portion (4) are resiliently collapsed, creating the recess (at 51') at that retained area (4e) in the vicinity of the lower end of the die piece (1a'), and as such, the base foaming material, which is in a liquid form and injected in the die unit, is flowed into such recess of velley or slope (s), with the result that, after curing the base material into a foam solid body, a projected area (51') is defined at the upper corner of resultant foam cushion member (5') and due to the projected area (51'), the corresponding corner area (43) of the seating surface portion (4), which lies upon the projected area (51'), is pulled outwardly to create an undesired projection area (P) as shown in FIG. 3. It is noted here that, after curing of the base foaming material, both intermediate die and upper die members (1') (3) are removed from the lower die member (2), and the side wall portions (4b) (4b) as well as the seating surface portion (4a) are turned back to a normal state from the inside-out state, as can be seen from FIG. 3.
Hence, in the molding or forming process above, it has been difficult to produce a given contour of seat accurately with a good curvature on its corners, and such projection area (P) has impaired the aesthetic appearance of the seat, by creating an unpleasing irregularity or wrinkles on the surface of the seat.
Further, as seen in FIG. 3, the side wall portion (4b) is not stretched neatly over the corresponding portion of the cushion member (5') due to the outwardly protrusion of the sewn jointed point (4f) and terminal end (4f) associated with the trim cover assembly (4). This results in a poor appearance of the seat.