of the plate 108 pulls the plate 92 downwardly thereby moving the contacts 91 87 and 87a to an open position as depicted in fig3 and 3a at this occurs the switch arm 31 continues to move to a full open vertical position and the transfer horns 41 and 46 part shock is effectively absorbed by operation of the damper springs 116 the envelope 57 is charged with an insulating gas such as sulfur hexafluoride to permit the passage of the gas between a chamber 131 of the housing 63 and a chamber 132 between the envelope and the housing the housing 63 is provided with a plurality of sets of ports 133 134 and 135 thus as the pistons 86 86a and 86b move downwardly in a contact opening operation they compress the insulating gas ahead of them as the gas pushed by the pistons moves through the cone bodies 73 73a and 73b respectively the fins 76 serve to prevent turbulence of the gas as it passes through the cone bodies of the stationary contacts each of the sets of ports 133 134 and 135 are associated with one of said stationary contacts thus the chamber 131 is subdivided into three piston chambers 137 138 and 139.