62 is mounted in a slidable piston assembly 64 in contrast to valve 12 of fig1 which is fixed in an immovable base more specifically valve 62 includes a head portion 62 a and a stem portion 62 b which extends into a central opening 64 b in the piston head 64 a to guide valve 62 in axial movement relative to piston head 64 a spring 66 biases slidable piston assembly 64 to the right against the pressure within the accumulator slidable piston assembly 64 can be moved to the left relative to valve body 65 and thereby close valve 62 on command by reducing the pressure at port 67 and within chamber 67 a from system high pressure at ports 69 and 70 to system low pressure at reservoir 71 when cpu 72 issues a command to close valve 62 electric power to control valve 73 generally referred to as a normally closed valve is terminated as in the previously described embodiments the choice of a normally closed valve for control valve 73 insures that the accumulator will shut off in the event of loss of electric power a fail safe design feature accumulator downstream pressure in chamber 68 is prevented from causing flow through port 74 to port 67 by check valve 75 an elastomer seal 76 is provided as a seat for poppet valve 62 spring 63 is calibrated to allow valve 62 to u201c slam shut u201d when the flow from the accumulator exceeds the maximum flow predetermined to be the maximum ever needed by the vehicle this third embodiment also has the capability to compare the pressure at.