Side bolster apparatus for automobile seat

1. A side bolster apparatus for a foldable seat back, the side bolster apparatus comprising:

a pressing unit formed in a lower portion of the seat back so as to provide an external force generated by rotating the seat back;

a bolster configured to protrude forwards from a rear side of the seat back; and

an external force transmitting unit connected to the pressing unit and receiving the external force from the pressing unit when the seat back is unfolded and transmitting the received external force to the bolster such that the bolster protrudes from the seat back,

wherein the bolster has a predetermined curvature in a longitudinal direction of the seat back;

wherein the external force transmitting unit includes:

an elevator raising or lowering the bolster with respect to the seat back;

a direction converter slidably coupled to the seat back and moving in substantially perpendicular direction to a movement direction of the elevator, wherein the direction converter has a slope so as to provide the external force to the elevator; and

a cable, wherein one end thereof is connected to the direction converter and the other end thereof is connected to the pressing unit; and

wherein the elevator includes:

a stationary guide fixed to the seat back such that the direction converter is displaceable thereto, wherein the stationary guide has a slit formed on one lateral side thereof in a direction where the bolster is raised or lowered; and

a movable guide slidably coupled to the stationary guide, one end of which is connected with the bolster and the other end of which includes a guide knob fitted into the slit of the stationary guide to move therein, the movable guide raised or lowered by the slope of the direction converter.

2. The side bolster apparatus according to claim 1 , wherein the direction converter includes a guide pin, one end of which is fixed to the seat back so as to guide motion of the direction converter along a designated path.

3. The side bolster apparatus according to claim 2 , wherein the other end of the guide pin is configured to pass through a portion of the direction converter to guide the motion of the direction converter.

4. The side bolster apparatus according to claim 2 , wherein the guide pin is aligned to be in substantially perpendicular direction to movement direction of the movable guide of the elevator.

5. The side bolster apparatus according to claim 1 , wherein the direction converter includes a first elastic member disposed substantially along a movement direction of the direction converter wherein the cable pulls the direction converter downward by the external force of the pressing unit and is restored to an original position thereof by a restoring force of the first elastic member when the external force of the pressing unit is removed so that the bolster returns to original position thereof.

6. The side bolster apparatus according to claim 5 , the elastic member is a compression spring.

7. The side bolster apparatus according to claim 1 , wherein the elevator includes a second elastic member disposed under the movable guide in the stationary guide and couples a lower portion of the movable guide and the seat back so that the movable guide is biased toward the seat back.

8. The side bolster apparatus according to claim 7 , the elastic member is an extension spring.

9. The side bolster apparatus according to claim 1 , wherein the cable includes a ball hooked on the pressing unit at the other end thereof, and the pressing unit includes a ball guide having a guide slot on a rotating path thereof such that the ball moves along the rotating path of the pressing unit, wherein the ball guide is formed at the seat frame.

10. The side bolster apparatus according to claim 9 , wherein the guide slot has an arcuate shape corresponding to the rotating path of the pressing unit.