at the same time the fluid in the lower chamber 48 flows through the vortex passages 210 and into the vortex chamber 206 in the bottom fitting 200 due to the fluid flow through the vortex passages 210 a vortex is generated in the vortex chamber 206 to produce an absorbing force against the shock the increase in fluid pressure in the fluid reservoir chamber 40 is partially absorbed by the compressible gas therein in the expansion stroke of the piston the fluid pressure in the upper chamber becomes greater than that of the lower chamber to cause fluid flow from the upper chamber 46 to the lower chamber 48 the fluid in the upper chamber 46 at first flows into the vortex chamber 118 via the vortex passages 104 the fluid flow in the vortex chamber 118 produces a vortex limiting the flow of fluid therethrough to produce an absorbing force against the shock at the same time due to expansion of the volume of the lower chamber the fluid pressure in the fluid reservoir chamber 40 becomes greater than that in the lower chamber 48 thus the fluid in the fluid reservoir chamber 40 flows through the bottom fitting 200 into the lower chamber 48 fluid flow in this direction is limited by the size of the vortex passage 210 to produce some absorbing force if the pressure difference between the fluid in the vortex chamber 206 and the fluid reservoir chamber 40 becomes greater than a set pressure of the coil spring 209 the disc shaped plate 204 is moved upwards to establish communication between the recesses 220 formed on the internal circumference of.