Gas pressure actuated switch with calibration means

Claim 1

A GAS PRESSURE ACTUATED SWITCH COMPRISING: MEANS HAVING AN INTERNAL WALL FORMING A PASSAGE, A VANE PIVOTALLY MOUNTED WITHIN SAID PASSAGE FOR SWINGING MOVEMENT ABOUT A HORIZONTAL PIVOTAL AXIS VERTICALLY SPACED FROM THE AXIS OF SAID PASSAGE AND EXTENDING TRANSVERSELY OF SAID PASSAGE, SAID VANE HAVING AN AREA LESS THAN THE INTERNAL AREA OF SAID PASSAGE TO PROVIDE FOR FLOW OF GAS THROUGH SAID PASSAGE SO THAT A PRESSURE DIFFERENTIAL IS PRODUCED BETWEEN OPPOSITE SIDES OF SAID VANE, SAID VANE HAVING A THICKENED EDGE ALONG A SUBSTANTIAL PORTION OF ITS PERIMETER WITH ITS GREATEST THICKNESS REMOTE FROM THE PIVOTAL AXIS OF SAID VANE AND TAPERING TO A MINIMUM ALONG THE TRANSVERSE EDGES OF SAID VANE TOWARD SAID PIVOTAL AXIS SO THAT THE TOTAL CLEARANCE AROUND THE VANE REMAINS SUBSTANTIALLY CONSTANT WHILE THE VANE SWINGS THROUGH A CONSIDERABLE ARC, AN ELONGATED MERCURY SWITCH TUBE MOUNTED ON SAID VANE AND PROJECTING LATERALLY THEREFROM WHEREBY TO ACT AS A COUNTERWEIGHT TENDING TO HOLD SAID VANE IN ONE DIRECTION FROM THE VERTICAL, SAID VANE BEING PIVOTALLY MOVABLE IN THE OPPOSITE DIRECTION TO SUCH AN EXTENT THAT THE MERCURY IN SAID SWITCH TUBE REVERSES ITS EFFECTIVE POSITION WHEN SAID PRESSURE DIFFERENTIAL INCREASES TO A PREDETERMINED VALUE, AND VARIABLE ORIFICE MEANS AT ONE END OF THE PASSAGE FOR PRODUCING AN ADJUSTABLE PRESSURE DROP DUE TO SAID FLOW OF FLUID THROUGH SAID PASSAGE TO ADJUST SAID PRESSURE DIFFERENTIAL BETWEEN THE OPPOSITE SIDES OF SAID VANE FOR A GIVEN TOTAL PRESSURE DIFFERENCE ACROSS SAID SWITCH.