Conventionally, as is shown in FIGS. 6 or 7, an automobile seat is constructed by a seat cushion 1, seatback cushion 2 and seat adjuster unit 3. When assembling, seat cushion 1 and seatback cushion 2 are independently formed in order to cover the cushions 1 and 2 by separate cover materials. As shown in FIG. 7, cushion material 5 of the seat cushion 1 is fixed on a seat cushion pan 4 and cover material 6 is put on the cushion material 5. The end portion 7 of the cover material 6 is put under the cushion pan 4 to be secured thereto by clip means 8.
As shown in FIG. 6, seatback cushion 2 includes cushion material and seatback frame (not shown) secured to the cushion material. Seat adjuster 3 is secured to the cushion and cover material 9 is attached over the seatback frame by clip means at an end portion 10 of the cover material 9. Cover 11 is finally attached to the assembly to form the seatback cushion 2. Seat cushion 1 is secured to the seatback cushion 2 by bolt means 12 through seat adjuster 3 which is integrally secured to the seatback cushion 2.
This conventional seat assembly, however, has a drawback that since the connection between the two cushion portions are made through bolt and pin connection at the relatively thin seat cushion pan, load concentration at the connecting portion will cause to reduction of rigidity and strength. If a reinforcement is attached to the connecting portion in order to cover the strength or rigidity, weight will be increased, which leads to the cost increase.