cushion the spring 15 and the spring seat 16 are installed in the lower housing 14 the wedge shaped spring fixing pin 17 is disposed at a position above the spring 15 and the spring seat 16 in use when the wedge shaped spring fixing pin 17 is released by the actuator 10 the elastic force of the spring 15 acts to push the spring seat 16 upwards in the alternative embodiment shown in fig3 b where the actuator 10 is installed at the rear end of the seat cushion the spring 15 and the spring seat 16 are installed in the upper housing 13 the wedge shaped spring fixing pin 17 is disposed at a position below the spring 15 and the spring seat 16 in use when the wedge shaped spring fixing pin 17 is released by the actuator 10 the elastic force of the spring 15 acts to force the spring seat 16 downwards in a preferred embodiment the wedge shaped spring fixing pin 17 is connected to a seat belt fig4 the wedge shaped spring fixing pin 17 disengages form the actuator 10 in accordance with movement of the seat belt thus when the seat belt is stretched tight as during a collision the wedge shaped spring fixing pin 17 disengages from the actuator 10 hereinafter the operation of an embodiment of the anti submarine seat for the automobile according to an embodiment of the present invention will be described in detail with reference to the.